DEPAR TMENT OF HUMANITIES & SCIENCE S PROGRAMMING FOR PROBLEM SOLVING MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY PROGRAMMING FOR

PROBLEM SOLVING DIGITAL NOTES B.Tech – I Year – I Semester R-20 DEPAR TMENT OF HUMANITIES & SCIENCE S

PROGRAMMING FOR PROBLEM SOLVING Preface C is a general -purpose programming language that is extremely popular, simple and flexible. It is machine -independent, structured programming language which is used extensively in various applications. C was the basic language to write everything from

opera ting systems (Windows and many others) to complex programs like the Oracle database, Python interpreter and more.

It is said that 'C' is a god's programming language. One can say, C is a base for the programming. If you know 'C,' you can easily grasp the k nowledge of the other programming languages that uses the concept of 'C' 'C' is a structured programming language in which program is divided into various modules. Each module can be written separately and together it forms a single 'C' program.

This struc ture makes it easy for testing, maintaining and debugging processes.

This digital notes is designed to be a stand -alone introduction to C, even if you've never programmed before. This notes has been organized to meet syllabi requirements of both JNTUH and AICTE. It serves as an introductory material to first year students, enabling them to understand basic concepts of C and updating them on the problem solving ability .

Organization of the book The content has been divided into five units, as per the syllabus.

Unit I – Introduction to Computer System, Problem Solving with algorithms and flowcharts Basics of C Language – History, Structure, Tokens, Data types, Control structures Unit II - Pointer basics, Arrays and Strings Unit III – Modu lar Programming using functions, Dynamic Memory Management Unit IV – Structures, Unions and Files

Unit V – Basic Data Structures – Stacks, Queues and Linked Lists We would like to extend our sincere gratitude to Dr. VSK Reddy, Principal, Malla Reddy Colle ge of Engineering and Technology (autonomous) under whose patronage we were able to write this book. We are also indebted to Dr.D.Sujatha, Head of the Department, Computer Science and Engi neering for her constant support and motivation for our academic growth.

With great pleasure we acknowledge the compatible environment shared by our colleagues I Year B. Tech CSE -I Sem L T/P/D C 4 -/-/- 3 PROGRAMMING FOR PROBLEM SOLVING USING C COURSE OBJECTIVES :

The students will be able to 1. Understand the use of computer system in problem solving and to build program logic with algorithms and flowcharts.

2. Explain the features and constructs of C programming such as data types, expressionsLoops, arrays, strings and pointers 3. Learn how to write modular Programs using Functions 4. Understand the use of Structures, Unions an d Files 5. Use basic data structures like stacks, queues and linked lists in designing applications

UNIT - I Introduction to Computing – Computer Systems, Computing Environments, Co mputer Languages, Algorithms and Flowcharts, Steps for Creating and R unning programs.

Introduction to C – History of C, Features o f C, Structure o f C Program, Character Set, C Tokens -keywords, Identifiers, C onstants, Data types, Variables. Operators, Expressions, Precedence and Associativity, Expression Evaluation, Type conversio n, typedef, enum Control Structures: Selection Statements ( Decision Making) – if and switch statements , Repetitio n Statements (Loops) - while, for, do -while statements , Unconditional Statements –

break, continue, goto. Command line arguments.

UNIT -II Pointers – Pointer variable, pointer declarati on, Initialization of pointer, a ccessing variables through pointers, pointer a rithmetic, pointers to pointers, void pointers Arrays – Definition , declaration of array, Initialization, storing values in array, two dimensional arrays, Multi -dimensional arrays. Arrays and Pointers, Array of pointers

Strings – Declaration and Initialization, String Input / Output functions, Array of strings, String manipulation functions , Unformatted I/O functions , strings and pointers DEPARTMENT OF HUMANITIES & SCIENCES PROGRAMMING FOR PROBLEM SOLVING UNIT -III

Designing Structured Programs using Functions - Types of Functions - user defined functions, Standard Functions, Categories of functions, Parameter Passing techniques, Scope – Local Vs Global, Storage classes , Recursive functions.

Passing arrays as parameters to functions , Pointers to functions , Dynamic Memory allocation , UNIT -IV Structures and Unions - Declaration, initialization, accessing structures, operations on structures, structures containing arrays, structures containing pointers, nested structures, sel f referential structures, array of structures, structures and functions, structures and pointers,

unions.

Files – Concept of a file, Streams, Text files and Binary files, Opening and Closing files, File input / output funct ions.Sequential Access and Random Access Functions UNIT -V Basic Data Structures – Linear and Non Linear Structures – Implementation of Stacks, Queues, Linked Lists and their applications.

Case Studies Case 1: Student Record Management System The main features of this project include basic file handling operations; you will learn how to add, list, modify and delete data to/from file.

Currently, listed below are the only features that make up this project, but you can add new features as you li ke to make this project a better one!  Add record  List record  Modify record

 Delete record Case 2: Library Management System This project has 2 modules.

1. Section for a librarian 2. Section for a student DEPARTMENT OF HUMANITIES & SCIENCES PROGRAMMING FOR PROBLEM SOLVING A librarian can add, search, edit and delete books. This section is password protected. That

means you need administrative credentials to log in as a librarian.

A student can search for the book and check the status of the book if it is available.

Here is list of fe atures that you can add to the project.

1. You can create a structure fora student that uniquely identify eachstudent. When a student borrows a book from the library, you link his ID to Book ID so that librarian can find how burrowed particular book.

2. You can create a feature to bulk import the books from CSV file.

3. You can add REGEX to search so that a book can be searched using ID, title, author or any of the field.

4. You can add the student login section.

TEXT BOOKS:

1. Mastering C , K.R. Venugopal , S R Prasad, Tata McGraw -Hill Education.

2. Computer Science: A Structured Programming Approach Using C, B.A.Forouzan and R.F.

Gilberg, Third Edition, Cengage Learning 3. Data Structures and Algorithms Made Easy by NarasimhaKarumanchi , Career Monk publications, 2017 REFERENCE BOOKS:

1. The C Programming Language, B.W. Kernighan and Dennis M.Ritchie, PHI.

2. Computer Programming, E.Balagurusamy, First Edition, TMH.

3. C and Data structures – P. Padmanabham, Third Edition, B.S. Publications.

4. Programming in C, Ashok Kamthane . Pearson Education India.

5. Let us C ,YashwanthKanethkar, 13th Edition, BPB Publications.

6. Data Structures using C by Aaron M. Tenenbaum, Pearson Publications 7. Data Structures using C by Puntambekar COURSE OUTCOMES:

At the end of the course the student will be able to 1. Understand a problem and build an algorithm/flowchart to solve it 2. Define variables and construct expressions using C language 3. Construct C programs using various conditional statements and loops 4. Develop efficient, modular programs using functions

5. Utilize arrays, structures and unions for storing and manipulating data 6. Make use of files and file operations to store and retrieve data 7. Design applications using basic data structures like stacks, queues and linked lists .

DEPARTMENT OF HUMANITIES & SCIENCES PROGRAMMING FOR PROBLEM SOLVING DEPAR TMENT OF HUMANITIES & SCIENCE S PROGRAMMING FOR PROBLEM SOLVING INDEX UNIT -I: Introduction to Problem Solving 4-75

Basics of C UNIT -II: Pointers, Arrays and Strings 76-95 UNIT -III: Functions 96-120 UNIT -IV: Structures, Unions and Files 121-152 UNIT -V: Basic data structures 153-176

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 1 Introduction to Problem Solving The computer allows us to do tasks more efficiently, quickly, and accurately than we could by hand. In order for this powerful machine to be a useful tool, it must be programmed. That is, we must specify what

we want done and how. We do this through programming.

A computer is not intelligent. It cannot analyze a problem and come up with a solution. A human (the programmer) must analyze the problem, dev elop the instructions for solving the problem, and then have the computer carry out the instructions.

Once we have written a solution for the computer, the computer can repeat the solution very quickly and consistently, again and again. The computer frees people from repetitive and boring tasks.

Steps in developing a solution Before starting to think about writing any programming code, we must first focus on the problem statement, that is, on the real-world domain . First we must understand the problem and then we try solving it. Once we think we have solved it we systematize our solution by writing it out in a more formal way as a series of steps (an algorithm ) that can be followed by another person.

Problem solving requires thinking about t he problem at a high level of abstraction while writing programming language code requires a very low level of abstraction DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 2 To write a program for a computer to follow, we must go through a two -phase process: problem solving

and implementation Problem -Solving Phase 1. Analysis and Specification: Understand (define) the problem and what the solution must do.

2. General Solution (Algorithm): Specify the required data and the logical sequences of steps that solve the problem.

3. Verify: Follow the steps exactly to see if the solution really does solve the problem.

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 3 Implementation Phase 1. Concrete Solution (Program): Translate the algorithm (the general solution) into a programming language.

2. Test: Have the computer follow the instructions. Then manually che ck the results. If you find errors, analyze the program and the algorithm to determine the source of the errors, and then make corrections.

Once a program has been written, it enters a third phase: maintenance.

Maintenance Phase 1. Use: Use the program.

2. Maintain: Modify the program to meet changing requirements or to correct any errors that show up while using it.

The programmer begins the programming process by analyzing the problem, breaking it into manageable pieces, and developing a general solution for each piece called an algorithm. The solutions to the pieces are collected together to form a program that solves the original problem.

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 4 UNIT -I Topics Covered:

Introduction to Computing – Computer Systems, Computing Environments, Computer Languages, Algorithms and Flowcharts, Steps for Creating and Running programs.

Introduction to C – History of C, Features of C, Structure of C Program, Character Set, C Tokens - keywords, Identifiers, Constants, Data types, Variables . Operators, Expressions, Precedence and Associativity, Expression Evaluation, Type conversion, typedef, enum Control Structures: Selection Statements(Decision Making) – if and switch statements, Repetition Statements (Loops) - while, for, do -while statem ents, Unconditional Statements –

break, continue, goto, Command line arguments.

INTRODUCTION TO COMPUTING Computer systems Computer is a digital electronic device which understands only 0’s and 1’s. It performs all arithmetic calculations (Addition, multiplication...) and non arithmetic calculations (copy, choose, move, compare….).

A computer is a system made of two components: Hardware and Software The computer hardware is the physical equipment. The software is the collection of programs (instructio ns) that allow the hardware to do its job. The computer manipulates these symbols in the desired way by following an intellectual map called program. A program is a detail set of humanly prepared instructions that directs the computer to function in a spec ific

way to produce the desired results. Computer intelligence quotient or I.Q is zero. It does not have any thinking, arguing or decision -taking power of its own. This power is intelligently conferred to it by proper programming methods by persons handling it.

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 5 Computer Hardware:

The hardware component of the computer system consists of five parts:

1. Input devices 2. Central processing unit (CPU) 3. Primary (Main) storage or Immediate Access memory Storage (I.A.S) 4. Output devices 5. Auxiliary storage devices or secondary memory or backing storage devices (floppy disk,

tape...) The input device is usually a keyboard where programs and data are entered into the computer. Examples of the other input devices include a mouse, a pen, or stylus, a touch screen, or an audio input unit.

The central processing unit (CPU) is responsible for executing instruction such as arithmetic calculations, comparisons among data, and movement of data inside the system.

Primary storage is a place where the programs and da ta are stored are erased when we turn off a personal computer or when we log off from a time -sharing computer.

The output device is usually a monitor or a printer to show output. If the output is shown on the monitor, we say we have a soft copy. If a print ed on the printer, we say we have a hard copy.

Auxiliary storage is used for both input and output. It is a place where the programs and data are stored permanently. When we turn off the computer, our programs and data remain in the secondary storage, read y for the next time we need them.

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 6 Computer Software:

Computer software is divided into two categories: system software and application software. System software manages the computer resources. It provides the interface between the hardware and the users but does nothing to directly serve the users need. Application software is a directly responsible for helping users solves their problem.

System Software:

System software consists of programs that manages the hardware resources of a computer and pe rform required information processing tasks. These programs are divided into three classes: the operating system, system support, and system development.

The operating system provides services such as a user interface, file and database access, and interfa ce to communication systems such as internet protocols.

System support software provides system utilities and other operating services.

System development software includes the language translators that convert programs into machine language for execution, debugging tools to ensure that the programs are error free.

Application software:

These are divided into two classes:

General -purpose software and Application -specific software DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 7 General -purpose software is purchased from a software developer and can be used for more

than one application. Examples like word processor, database management systems.

Application -specific software can be used only for its intended purpose. A general ledger system used by accountants and a material requirem ents planning system used by a manufacturing organization are examples.

Figure: Relationship between System software and Application software Computing Environments In the early days of computer, there is only one environment: the mainframe computer hidden in a central computing department. With the advent of minicomputers and personal computer, the environment changed, resulting in computers on virtually every desktop.

Personal Computing Environment:

In 1971, Ma rcian E. Hoff, working for Intel, combined the basic elements of the central processing unit into the microprocessor. This first computer on a chip was Intel 4004 and was the grandparent many times removed of Intel’s current system.

H/w Application software System software USER DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving

MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 8 If we are using a perso nal computer, all of the computer hardware components are tied together in our personal computer(PC for short).we have whole the computer for ourselves and we can do whatever we want.

Time -Sharing Environment:

Employees in large companies often work in what is known as time -sharing environment. In the time -sharing environment, many users are connected to one or more computers. A typical college lab in which a minicomputer shared by many students. In the time -sharing environment, all computing must be don e the central computer. In other words, the central computer has many duties: It must control the shared resources; it must manage the

shared data and printing; and it must do the computing.

Client/Server Environment:

A client server computing environm ent splits the computing function between a central computer and user’s computers. The users are given personal computers or workstation so that some of the computations responsibility can be moved from the central computer and assigned to the work station s. In this, the micro computers or work stations are called the client. The central computer, which may be a powerful microcomputer, minicomputer, or central main

frame systems, is known as the server.

Distributed Computing:

A distributed computing environment provides a seamless integration of computing functions between different servers and clients. The Internet provides connectivity to different servers throughout the world. Example like eBay.

Computer languages Low Level Language: The only programming language available was machine languages. Each computer has its own machine language which is made of streams of 0’s and 1’s. The only language understood by computer hardware is machine language.

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 9 1. Middle Level Language: The programs are written using the instructions of CPU is called Assembly level language. It uses symbols, or mnemonics, to represent the various machine language instructions. Examples are TASM,MASM

2. High Level Language: In the Assembly level language programmers need to concentr ate on the hardware so it is tedious because each machine instruction had to be individually coded. So the High level language was developed it is English like language where instruction typically translates into machine language instructions.

Creating and Running Programs The procedure for turning a program written in C into machine language. These steps are repeated many times during development to correct errors and make improvements to the code.

Writing and Editing Programs:

The software used to write programs is known as text editor. A text editor helps us enter, change, and store character data. Depending on the editor on our system, we could use it to write letters write programs. The main difference between the text processing and program writ ing is that program are written using lines of code, while most text processing is done with characters and lines. After complete a program, we save our file to disk. This file will

be input to the compiler; it is known as a source file.

Compiling Programs :

The code in a source file stored on the disk must be translated into machine language. This is the job of the compiler. The C compiler is actually two separate programs: The Preprocessor and the translator The preprocessor reads the source code and prep ares it for translator. While preparing the code, it scans for special instruction known as preprocessor commands. These commands tell

the preprocessor to look for the special code libraries, make substitutions in the code, and in other ways prepare the co de for translation with machine language. The result of preprocessing is called the translation unit. After the preprocessor has prepared the code for compilation the translator does the actual work of converting the program into machine DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving

MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 10 language. An objec t module is the coding machine language.

Figure: Building a C Program DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 11 Linking Programs:

As we will see late, a C Program is made up of many functions. We write some of these functions, and they are a part of our source program. However, there are other functions, such as input/output process and mathematical library functions that exists else where and must be attached to our program. The linker all of these functions, ours and system’s, into pour final executable programs.

Executing Programs:

Once our program has been linked, it is ready for execution. To execute a program, we use an operating system command, such as run, to load the program into primary memory and execute it. Getting the program into memory is the function of an operating sy stem program known as the loader. It locates the executable program and reads it into memory. When everything is loaded, the program takes control and it begins execution. In today’s integrated

development environment, these steps are combined under one m ouse click or pull -down windows.

In typical program execution, the program reads data from processing, either from the user or from a file. After the program process the data, it prepares the output. Data output can be to the user monitor or to file. When the program has finished its job, it tells the operating system, which then removes the program from the memory.

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 12 Algorithms An algorithm is a step -by-step procedure for solving a problem using pseudocode. The Pseudocode we present here is particularly useful for developing algorithm that will be

converted to structured C programs.

Features of an algorithm:

Finiteness : An algorithm terminates after a fixed number of steps.

Definiteness : Each step of the algorithm is precisely defined.

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 13 Effectiveness : All the operations used in the algorithm can be performed exactly in a fixed duration time.

Input : An algorithm has certain precise inputs before the execution of the algorithm begins.

Output : An algorithm has one or more outputs Pseudo code Pseudo code is similar to everyday English; Pseudo code is an artificial and informal language that helps programmers develops algorithms. It is convenient and user -friendly although it is not an actual computer programming language. Pseudo code programs are not actually

executed on computers. Rather, they merely help the programmers “think out” a program before attempting to write it in a programming language such as C.

Steps to follow i n writing pseudo code:

 Mimic good code and good English. Variable names should be mnemonic, include comments where it is useful.

 Ignore unnecessary details. Use some convention to group statements.(begin/end, brackets).

 Take advantage of programming short hands. Using if -else or looping structures is more concise.

 Consider the context.

Example: 1 An algorithm /Pseudo code to add two numbers.

Step 1: start Step 2: Read the two numbers into a, b Step 3: c = a + b Step 4: write/print c Step 5: stop.

Example 2: An algorithm /Pseudo code to find whether a given number is odd number or a even number.

Step 1: Start Step 2: Read the number n Step 3: If (n % 2) = 0 then Write n is even number Go to step 5 Step 4: write n is odd number

Step 5: Stop DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 14 Start Read a, b

c= a + b Write c Stop Flow Chart A flow is a graphical representation of an algorithm or a portion of an algorithm. Flowcharts are drawn using certain special -purpose symbols such as rectangles, diamonds, ovals, and small

circles as shown below. These symbols are connected by arrows called flowlines. Like pseudo code, flowchart is useful for developing and representing algorithms, although, pseudo code is performed by most programmers. Flowcharts clearly visually a how control structures operate in a program. The m ost common symbols used in drawing flow charts.

Uses of flowcharts:

 Flowcharts are an excellent means of communication and they impart ideas to others.

 Flowcharts provide an overview of the entire problem and its algorithm for solution.

 Flowcharts are quick method of illustrating program flow and show all major parts of a program.

 Flowcharts facilitates coding and modification of programs  Flowcharts provide a permanent recording of program logic.

Example 1: Flowchart for addition of two numbers.

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 15 Example 2: Flowchart to find whether a given number is odd or even.

INTRODUCTION TO C LANGUAGE History of C C is a structured programming language. It is considered a high -level language because it allows the programmers to concentrate on the problem at hand and not worry about the machine that the program will be using. C, like modern languages, is derived from ALGOL. the first language to use a

block structure. ALGOL is used in Europe but not in America this leads to the development of Structured programming languages. In 1967, Martin Richards developed a language called Basic Combined Programming Language, or BCPL. Ken Thompson followed in 1970 with similar language he simply called B. B was used to developed the first version of the UNIX, one of the popular network operating system in use today. Finally, Dennis M. Ritchie developed C, which took many concepts from

ALGOL, BCPL, and B and added the concept of data types.

Start Read n If(n%2)==0 Write n is even number Write n is odd number

Stop DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 16 The history of ‘C’ started in 1972 by the BELL Laboratories, USA., Where Dennis M.Ritchie proposed this language. The growing popularity of ‘C’, the changes in the language over the

years and the creation of compilers by groups not involved in its design, combined to demonstrate a need for a more precise and more contemporary definition of the language. In 1983, the American National Stand ards Institute (ANSI) established a committee whose goal was to produce “An unambiguous and machine - independent definition of the language C”. The result is the ANSI standard for C.

Structure of a C Program: Every C program contains a number of several bu ilding blocks known as functions. Each function of it performs task independently. A function is subroutine that may consists one or more statements.

Example of a simple C program:

/* Program Listing welcome.c A simple program in ‘C’*/ line 1 #include line 2 main() line 3 { line 4 printf (“ Welcome to C programming \n”); line 5

} /*End of main () */ line 6 Output: Welcome to C Programming DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 17 Documentation section:

To enhance the readability of the program, programmers can provide comments about the program in this section. Comments can be used any where in the program but too many comments are avoided. It is useful for documentation. This gives the clarity of the program can be followed if it is properly documented. The comments can be inserted with a single statement or in nested statements.

Examples /* This is a single comment*/ /*This is a example of/*nested comments*/*/ From above example: line 1 DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving

MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 18 /* Program Listing welcome.c A simple program in ‘C’*/ Header file section : C program depends upon some header files for function definition that are used in program. A header file contains the information required by the compiler when calls to the library functions used in the program occur during compilation. Each heade r file by default

is extended with .h. The file should be included using #include directive.

Example: line 2 #include or #include “stdio.h” In this example file is included i.e. all the definitions and prototypes of functions defined in this file are available in the current program. This file is compiled with original program.

Global declaration section: This section declares some variables that are used in more than one function. These variables are known as global variables. These m ust be declared outside of all the functions.

Main program section: Every program written in C language must contain main() function.

Empty parenthesis after main is necessary. The function main() is starting point of every ‘C’ program. The execution of th e program always begins with the function main(). Except the main () function, other sections may not be necessary. The program execution starts with the opening brace ( { ) and ends with the closing brace ( } ). Between these two braces the programmer sho uld declare the declaration part and the executable part.

Declaration Part: the declaration part declares the entire variables that are used in executable part.

The initialization of variables also done here. The initialization means providing the initial value to the variables  Executable Part: This part contains the statements following the declaration of the variables. This part contains a set of statements. These statements are enclosed between the braces.

Examples: line 3, line 4, line 5, line 6 DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 19 User -defined function: The function defined by the user is called user defined function. These functions are generally defined after the main() function. They can also be defined before

main() function. This portion in not compulsory.

Rules of a C language  C is made of functions.

 A function is a set of statements which perform a specific task(job)  Structure of a function definition: A function will have a name.

 A C statements ends with a semi -colon (;) which indicates to the compiler end of the statement.

 Most of the statements are placed with in a function with few exceptions.

 main () is a special type of function and its specialty is every program should contain one and only main function. main () indicates the starting point of program.

i. A part from main() function. There are two types Standard Library functions:

They are also called as ready maid function or built in function.

Examples: printf(),scanf(),sqrt()….

ii. User -defined functions: These functions have to be defined by the programmers.

 Average of compiler provide 500 functions  C language is case -sensitive but not space -sensitive.

 ANSI C has 32 keywords called as reserve words Note: Though main () is not a keyword it has to be written in lower case letter.

 A C statement is one of the following:

 An expression l.variable=R.value Example: z=x+y; x=5;  A call to a function Example: printf (“Welcome”);

y=sqrt(x);  Combination of both the above i.e. it can be expression and a call to a function Example:

z= x+sqrt(y); DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 20 Characteristics of ‘C’ language Or Features of ‘C’ language 1. Modularity

2. Extendability 3. Portability 4. Efficiency and Speed 5. Flexibility Modularity: Ability to break down large modules into a manageable sub modules. It is one of

the important features of the structured programming languages.

Example: calculator can be divided into arithmetic and trigonometric and again that is divided into sub modules.

Advantages:

 Different persons with different roles can be involved in developing the project.

 The project can be completed with in given period of time.

 Debugging will become easier.

 Software maintenance become easier because of plug -out and plug in features.

 C is highly structured language.

Extendability: Ability to extend an existing software by adding new features is called extendabiltiy. It is a by product of modularity.

Portability: Ability to port (install) existing software in different platforms (Unix, dos etc.) is called portability. It means that the programs written on one machine can be executed on different machine with or without minor changes in the program.

Efficiency and speed: C language has rich set of data types and operators making the language DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 21 more efficient and fast. The language provides some operators example: increment and decrement operators) which speed up the execution to large extent. Further, it also provides

user defined data types (example: structures) through which miscellaneous data can be easily manipulated.

Note: Though C is a high level language often it is called as middle level language because programs written in c language run at the speeds matching to that of the some programs written in assembly level language. Due to this reason C language is widely used in developing system software.

Flexibility: keywords are for computer languages. ASCI C complier has only 32 keywords. These are the basis building blocks of the programming language. C is also called as programmers’ language. With 32 keywords a programmer is able to solve any type of task due to this reason programmers have the compl ete control over the language their by gaining the flexibility.

Note: C program run faster and occupy less space, they are widely used in mobile technology, telecommunications, embedded systems.

C Tokens:

In a Passage of text, individual words and punctuation marks are called as tokens. In a C program, the smallest individual units are known as C tokens. The following are different categories of C tokens.

1) Keywords 2) Identifiers 3) Constants 4) Operators.

Keywords:

Keywords are also known as reserve words. These keywords are only to be used for their intended purpose and as identifiers. All the Keywords are lowercase.

Example: auto, char, int, long, goto, return, register…etc Note: The keywords with at least one uppercase letter can be used as an identifier.

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 22 Identifiers:

Identifier allows us to name data and other objects in the program. Different programming languages use different syntactical rules to form identifiers. In C, the rules for identifiers are very simple. The only valid names symbols are the capital letter A through Z, the lowercase letters a through z, the digits 0 and 9, and the underscore. The first character of the identifiers cannot be a digit. The last rule is that the name we create cannot be keywords. C allows names

to be up to 63 characters long.

Rules of identifiers 1. An identifier must start with a letter or underscore: it may not have a space or a hypen.

2. C is a case -sensitive language Variables A variable is a place holder that occupies some part of the memory which can initialize or assigned or changed during the execution of the program.

Declaration of variables Syntax : datatype variable _name(s); Example : float price; Here price is a variable which hold a float value.

Initialization of variable Syntax: data type variable_name(s) = value; Example: int x=5; Here x is a variable which holds a value=5; Rules & conventions for naming the variables :

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 23 1. Variable should always be declared at the beginning of the functions.

2. A variable name should begin with alphabet or underscore. And the remaining character can be alphabets digits or underscore.

3. A variable name can’t exceed 31 characters 4. Special characters are not allowed with in the variable name including spaces. Expect underscore.

5. Keywords cannot be used as variable names Conventions 1. Declare variable names in lowercase letters 2. Variables names should provide a hint on what it is going to hold.

Examples of valid and invalid variables:

Valid variables Invalid variables int a2; int _a1; double a_b_c; float 1a; int a b c;

int abc$; double $abc; Note: Uninitialized variables contain junk or garbage values.

Constants A constant is a value that doesn’t change during the execution of a program. These are generally declared before main function.

Constants DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 24 Numeric constants String constant Character constant Integer constant Real constant

Integer constant: Numeric value without decimal part is called integer constant.

Example: 5, -66 Real constant: Numeric value with decimal part is called as real constant. The precision of a real value indicates number of digits after decimal point. Example: 5.0, - 98.76… Character constant: A single character enclosed in single quotes is called as character constant.

Character Set Alphabet: a-z A-Z Digits: 0 -9 Special characters: $, ?, ; , , …..

Example: ‘a’, ‘5’, Declaration of a constant Syntax: const data type constant_name= value; Example: const float PI=3.14159; Note: In an 8 bit character set, a character occupies 1 byte. Where as in 16 bit character set, a

character occupies 2 bytes. Character constants have integer values known as ASCII values DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 25 Complex Imaginary Real Derived Floating -point (ASCII -American Standard code for Information Interchange).Since each char acter represents an integer value, it is also possible to perform arithmetic operations on character constants.

Spacebar is also a character constant.

String constant: A single character or a group of characters enclosed in double quotes is called string c onstant.

Example: “5” , “temperature” Note: Character constant occupies 1 byte where as string constant occupies 2 bytes.

Backslash Character constants : C supports some special backslash character constants that are used in output functions. These are al so known as escape sequences .

‘\a’- audible alert(bell) ‘\v’- vertical tab ‘\b’- backspace. ‘\’’- single quote.

‘\f’- form feed ‘\”’- double quote.

‘\n’- new line ‘\?’- question mark ‘\r’- carriage return ‘\0’- Null Data Types A data type consists of the values it represents and the operations defined upon it. The C language has defined a set of data types that can be divided into four general categories: void,

integral , floating -point, and derived as shown below Integral void C Data Types DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 26 Integer Character Boolean

Figure: Data Types Void type:

The void type, designated by the keyword void, has no values and no operations, although having no values and operations might seem unusual. It can also be used to define that a function has no return value.

Integral type The C language has three integral types: Boolean, character, and integer. Integral types cannot contain a fraction part; they are whole numbers.

 Boolean: Boolean type can represent only two values: true or false. C used integers to represent the Boolean values: a nonzero number (Positive or negative) was used to represent true, and zero was used to represent false. The Boolean type, which is referred to the keyword bool, i s stored in memory as 0(false) or 1(true).

 Character: A character is any value that can be represented in the computer’s alphabet, or as it is better known, its character set. An 8 -bit character set represent up to 256 characters.

 Integer: An integer type is a number without a fraction part. C supports four different sizes of the integer data types:

 Floating -Point Types The C standard recognizes three floating –point types: real, imaginary, and complex.

 Real: The real type holds values that consist of an in tegral and a fractional part. The C language supports three different sizes of real types: float, double, and long double.

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 27  Imaginary type: An imaginary number is used extensively in mathematics and engineering. An imaginary number is a real number multipli ed by the square root of - 1. Most C implementations do not support the imaginary type.

 Complex: Complex number is a combination of real and imaginary number.

DATA TYPE STORAGE SIZE IN BYTES RANGE FORMAT SPECIFIER 16 BIT Compiler 32 BIT Compiler 16 BIT

32 BIT short int or signed short int 2

2 -32768 To 32767 (-215 to +215 -1) -32768 To

32767 (-215 to +215 -1) %hd short int or

signed short int 2 2 0 to 65535 (0 to +216 -1) 0 to 65535 (0 to +216 -1)

%hu signed int or int 2

4 -32768 To 32767 (-215 to +215 -1) -2,147,843,648 to

2,147,843,647 (-231 to +231-1) %d or %i unsigned int 2 4 0 to 65535

(0 to +216 -1) 0 to 4,294,967,295 (0 to232-1 ) %u long int or signed long int

4 4 -2,147,843,648 to 2,147,843,647 (-231 to +231-1) -2,147,843,648

to 2,147,843,647 (-231 to +231-1) %ld unsigned long int 4 4 0 to 4,294,967,295

(0 to232-1 ) 0 to 4,294,967,295 (0 to232-1 ) %lu long long int or signed long long

int Not supported 8 -------- -

922337203685477580 8 To 922337203685477580 7

(-263 to +263-1) %Ld char or signed char 1

1 -128 to 127 (-27 to 27 1) - -128 to 127 7 7 (-2 to 2 -1) %c

Unsigned signed char 1 1 0 to 256 (0 to 28-1) 0 to 256 (0 to 28-1) %c DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 28 Derived data types:

Derived datatypes are used in ‘C’ to store a set of data values. Arrays , Structures , Union and pointer are examples for derived data types.

User -defined data types:

The data types defined by the user are known as the user -defined data types. C provides two identifiers typedef and enum to create new data type names typedef:

It allows the user to define an identifier that would represent an existing data type.

The user -defined data type identifier can later be used to declare variables.

Syntax: typedef type identifier; For Example, the declaration , typedef int Integer; makes the name Integer a synonym of int.Now the type Integer can be used in declarations ,type castings,etc like

Integer num1,num2; Which will be treated by the C compiler as the declaration of num1,num2a s int variables.

“typedef” ia more useful with structures and pointers.

Enumeration:

An enumerated type (also called enumeration or enum) is a data type consisting of a set of named values called elements, members or enumerators of the type.

The enumerator names are usually identifiers that behave as constants in the language. A DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 29 variable that has been declared as having an enumerated type can be assigned any of the enumerators as a value. In other words, an enumerated type has values that are different from

each other, and that can be compared and assigned, but which are not specified by the programmer as having any particular concrete representation in the computer's memory; compilers and interpreters can represent them arbitrarily.

The enume ration data type is defined as follows:

Syntax: enum identifier {value1,value2,……valuen}; Identifier: it is a user defined enumerated data type which can be used to declare variables that can have one of the values enclosed within the braces ( enumeration constants ).

Declaration of variables of this new type:

Ex:

enum week{ sunday, monday, tuesday, wednesday, thursday, friday, saturday}; declaration of variable:

enum week today; today=wednesday; Example of enumerated type #include enum week{ sunday, monday, tuesday, wednesday, thursday, friday, saturday}; int

main() { enum week today; today=wednesday; printf("%d day",today+1);

return 0; } Output 4 day DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving

MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 30 Operators:

Operators are C tokens which can join together individual constants, variables, array elements and functions references. Operators act upon data items called operators.

C operators are classified into following categories:

1. Arithmetic operators 2. Relational operators 3. Logical operators 4. Assignment operators 5. Increment and decrement operators

6. Conditional operators 7. Bitwise operators 8. Special operators Arithmetic operators:

Arithmetic operators Meaning + - *

/ % Addition or unary plus Subtraction or unary minus Multiplication Division

Modulo division DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 31  For arithmetic operations, operands must be numeric values.

 Here modulo division produces remainder of integer division Arithmetic operations are classified as  Integer arithmetic  Real arithmetic  Mixed mode arithmetic

Integer arithmetic: Both the operands are integer in an integer arithmetic. It always yields an integer value.

Example: a+b, a -b Real arithmetic: Both the operands are real in real arithmetic. It yields real value as result. It cannot be applied to % operator.

Example: float a=20.0, b= 3.0 a+b= 20.0+3.0=23.000000 a/b=20.0/3.0=6.6666667 a%b=20.0%3.0(invalid expression) Mixed mode arithmetic: when one is integer and other is real it is known as mixed mode arithmetic.

Here, result will always be real.

Example: int a=20.0, b=3; a+b= 20.0+3=23.0 a/b=20.0/3=6.666667 a%b=20.0%3 (invalid expression) DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving

MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 32 Relational operators:

Relational operators Action < <= > >=

== != Is less than Is less than or equal to Is grater than Is grater than or equal to

Is equal to Is not equal to Example 1) 38<4 = 0 false 2) 38>4 =1 true

Logical operators:

Logical operators Action && || ! Logical AND Logical OR

Logical NOT  Logical expression combines two or more relational expressions.

 Logical operators are used to test more than one condition and make decision.

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 33 Logical AND: The result of the logical AND expression will be true only when the relational expressions are true.

Syntax: Exp1 && Exp2 Example: if a=10, b=5, c=15 1. i=(a>b)&&(b

2. i=(a

Logical OR: The result of logical OR expression will be true only when both the relational expressions are false.

Syntax: Exp1||Exp2 Example:

if a=10,b=5,c=15 1. i=(a

2. i=(ac); The value of i in this expression will be 0.

Logical NOT: the result of the expression will be true, if the expression is false and vice versa.

Syntax: !Exp2 Example: x=20 i = !(x==20) The value of i will be 0. This is because x==20 is true(value 1).

Assignment operators:

The operators are used to assign result of an expression to a variable. Syntax:

variable op=exp; OR variable=variable op exp; Example:

1. a=a+10; or a+=10; adds 10 to a and assigns the value to a.

2. a=a*(b+5) or a*=b+5 multiplies b+5 with a and assigns result to a DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 34 Increment and Decrement operators: These operators are represented as ‘++’ and ‘ --’. ‘++’ increments operand by 1 and ‘ --’ decrements operand by 1. They are unary operators and take

the following form.

Examples:

1. int a=9; y= ++a; The value of y will be 10; 2. int a=9; y=a++; The value of y will be 9; Operator Action

a++ ++a a- - --a Post -increment Pre-increment

Post -decrement Pre-decrement Conditional operator: It is also known as ternary operator.

Syantax: Exp1 ? Exp2 : Exp3; where exp1,exp2,exp3 are expressions. Example:

int a=5,b=10,c=15; y = (a>b) ? b : c; DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 35 In the above statement, the expression a>b is evaluated since; it is false value of c will be

assigned to y. so value of y will be 15.

Bitwise operators:

Bitwise operators are similar to that of logical operators except that they work on binary bits.

When bitwise operators are used with variables, they are internally converted to binary numbers and then bitwise operators are applied on individual bits. Bitwise operators do manipulation on bits stored in memory. These operators work with char and int data types.

They cannot be used with floating point numbers.

Bitwise operators Action & | ^ <<

>> ~ (unary) Bitwise AND Bitwise OR Bitwise exclusive OR Shift left

Shift right Ones complement Example: if a=4, b=6; The equivalent binary value of a is 0000 0100 The equivalent binary value of b is 0000 0110

a) The value of a&b = 0 0 0 0 0 1 0 0 b) The value of a|b= 0 0 0 0 0 1 1 0 c) The value of a^b = 0 0 0 0 0 1 0 1 d) a<<2. It left shifts the binary bits twice. Therefore a= 0 0 0 1 0 0 0 0 DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving

MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 36 e) a>>2. It right shifts the binary bits twice. Therefore a = 0 0 0 0 0 0 0 1 f) ~a. Unary operator which performs logical negation on each bit, 0’s will be converted to 1’s and 1’s to 0’s. Therefore a will become 1 1 1 1 1 0 1 1 Special operators:

There are some special operators available in C such as,  Comma operator  Sizeof operator  Member selection operators (. and ->) Comma operator: The comma operator ‘ , ’ has the lowest priority among all the operators

available in C. This operator is used to separate the related expressions. The expressions separated by comma operator need not be included within the parenthesis.

Example: c= (a=5, b =10, a+b); This expression first assign 5 to a, then assigns 10 to b and finally (5+10) to c.

Sizeof operator: It returns number of bytes the operand occupies. Operand may be a variable, a constant, or a data type qualifier.

Syntax: sizeof (operand); Example: y= sizeof (int); here value of y will be 2 bytes Member operators: These are used to access members of structures and unions.

Example:

Var.member1; // when va r is a structures variable.

Var->members2; // when var is a pointer to structures variable.

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 37 Points to be remembered on operators:

• Unary operator: It requires only one operand.

• Binary operator: It requires two operands like a+b, a -b,a*c etc.

• Logical operator: Used to compare two or more operands. Operands may be variable constants or expression.

• Assignment operator: Used to combine the results of two or more statements.

• Conditional operator: Checks the condition and executes the statement depending on the condition.

• Bitwise operator: Used to manipulate the data at bit level. It operates on integer only. It may not be applied to float or real.

Input/output Functions Input and output operations on data can be done by using input and output functions. An input function reads data from keyboard and stores in the variable where as output function prints value in the variable on the screen These functions are classified into two categories.

1. Formatted input/output functions(IO) 2. Unformatted input/output functions(IO) FORMATTED I/O FUNCTIONS •Formatted functions read and write all types of data values. format specifier are used to identify the data type to read or written into variables.

Formatted Input function:

Formatted input function accepts an input data that has been arranged in a particular format through keyboard.

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 38 scanf() is the formatted input function The general form or syntax of the scanf( ) is scanf("format specifier",&variable);

scanf function consists of two parts.

first part in scanf function is format specifier enclosed within double quotes. format specif ier is used to specify the type of format accepted by the scanf to the specified variable. format specifier starts with "%" followed on or two characters ex: %d is for accepting signed integers Second part in scanf () is list of variables. All variables are preceded with an ampersand(&)

symbol. ampersand is address operator which directs scanf() to store read value at the memory address of the variable.

format string(Control string): Group of format specifiers are called as format string or control string . if scanf() has to read multiple values from keyboard then all format specifiers are grouped to form format string as show below ex: scanf("%d%%d%d",&v1,&v2,&v3); The above example reads three integers one by one from keyboard into variable v1,v2,v3

respe ctively Formatted Output function: This prints data on the console(output screen).

printf() is the formatted output function.

printf ( ): This function prints all type of data values to the console.

it consists of two sections. first section contains format string and next part contains list for corresponding variables for specified format string.

Syntax: printf(“format string”,arg1,arg2….argn); The control string consists of • Characters that will be printed on the screen as they appear.

• Format specifiers that define the output format for display each data item.

• Escape sequence characters such as \t, \n, \b etc.

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 39 arg1,arg2…..argn are the list of variables whose values has to be printer on to screen Note: The arguments should match in number, o rder and type with the format specifications.

Output of Integer Numbers:

List of format specifiers:

Format specifier Data type %hd signed short int Or short int or short %hu unsigned short int %d or %i signed int Or int %u unsigned int

%ld long int or signed long int %lu unsigned long int %Ld long long int Or signed long int %Lu unsigned long long int %o or %O octal integer

%x or %X Hexa decimal integer %c char %f float %lf double %Lf long double

%s String(group of characters) %e Print float value in exponential form.

%g Print using %e or %f whichever is smaller %e Print float value in exponential form DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 40 The format specifier can also contain sub -specifiers: flags, width, .precision and code

% FLAG WIDTH MODIFIER Precision SIZE CODE flags Description - Left-justify within the given field width; Right justification is the default (see width sub- specifier).

+ Forces to preceed the result with a plus or minus sign (+ or -) even for positive numbers. By default, only negative numbers are preceded with a - sign.

width Description (number) Minimum number of characters to be printed. If the value to be printed is shorter than this number, the result is padded with blank spaces. The value is not truncated even if the result is larger.

.precision Description . Separates the fractional part.

If the period is specified without an explicit value for precision , 0 is assumed.

Size Allocates no of positions for fractional part CODE using conversion symbol for data type Ex: Output of the number 1234.

#include void main ( ) { printf(" \n%d",1234); //Without field width printf(" \n%6d",1234); // Right alignment

printf(" \n%-6d ",1234); //Left alignment printf(" \n%012d",1234); //Padding with Zero DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 41 printf(" \n%2d",1234); //Ov erriding the field width value.

} For floating point l Number:

The output of a real number may be displayed in two ways:

1. Decimal Notation ex: 2.345, 0.000005, -2.8976, 3456.987 etc.

2. Exponential Notation Output of Real Number in decimal notation: %w.p f Here both w and p are integers.

The integer w indicates the minimum number of positions that are to be used for display of the value.

The integer p indicates the number of digits to be displayed after decimal point (precision). The value when disp layed is rounded to p decimal places and printed right -justified in #include int main() {

float y= 98.7654; printf(" \n %f", y); printf(" \n%7.4f",y); printf(" \n%7.2f",y); printf(" \n%-7.2f",y);

return 0; } DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 42 Printing of a single character:

The format specification for printing a character is:

#include int main() { printf(“%c”,’S’); printf(“ \n%3c”,’S’);

printf(“ \n%6c”,’S’); return 0; } S S

UNFORMATTED IO FUNCTIONS INPUT FUNCTIONS 1.getch() 2.getche() 3.getchar()

4.gets() 1. getch(): - reads a character from keyboard and it does not require pressing of enter key after entering a key, entered character is not displayed on console S DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving

MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 43 char ch; ch=getch(); 2. getche(): - reads a character from keyboard and it does not require p ressing of enter key after entering a key, entered character is echoed back on to the console

char ch; ch=getche(); getch() and getche() are available in the header file conio.h (console input output header file) 3. getchar(): -reads a character from keyboard and it requires pressing of enter key

char ch; ch=getchar(); 4. gets(): -reads a string from keyboard char ch[10]; gets(ch); OUTPUT FUNCTIONS:

1.putchar() 2.puts() 3.putch() 1. putchar(): -prints a character on to the screen char ch;

ch=getchar(); putchar(ch); 2. puts(): - prints a string on to the screen char ch[10]; gets();

puts(ch); DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 44 3. putch(): -prints a character on to the screen char ch;

ch=getchar(); putch(ch); Expressions An expression consists of a single entity such as a constant, a variable, an array element or a reference to a function or can be a combination of such entities joined together using one

or more operators. An expression can also represent logical condition, that is true or false, which can be represented using integer value like ‘1’ and ‘0’ respectively. Expressions can be simple or complex. An operator is a syntactical token that requires an action be taken. An operand is an object on which an operation is performed; A simple expression contains only one operator.

Example: 2+5=7 ; A complex expression contains more than one operator. Example:

2+6*8=50 Here a priority comes into picture with precedence. The order in which the operators in a complex expression are evaluated is determined by a set of priorities known as precedence.

Higher the precedence that expression will be calculated first. If two operators with the same precedence occur in a complex expression. Another attribute of an operator, its associativity, takes control. Associativity is parsing direction used to evaluate an expression. It can be either left-to-right or right -to-left.

Note : when two operators having same precedence occur in an expression and their associativity is left -to-right.

We can divide the simple expression into six categories.

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 45 Expression Categories Primary Postfix Prefix Unary Binary Ternary

Examples:

1. c=a+b*d; 2.

x==y; 3. x+=y; Note: An expression always reduces to single value.

Primary Expressions: A primary expression consists of only one operand with no operator. In c, the operand in the primary expression can be name, a constant, or a parenthesized expression.

Names: A name is any identifier for a variable, a function or any other object in the language.

The following are examples of some names used as primary expressions:

Examples: a, b12, price, calc, INT_MAX, size etc.

Literal constants: A constant is a piece of data whose value can’t change during the execution of the program.

Examples: 5, 123.98, ‘A’ Parenthetical expressions: Any value enclosed in parentheses must be reducible to a single value and is therefore a primary expression.

Examples: (2+3+4), (a=23+b*6) DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 46 Postfix Expressions: The postfix expression consists of one operand following by one operator.

Postfix increments/decrements: The postfix increments and p ostfix decrements are also postfix operators. The value of the postfix increment expression is determined before the variable is increased. For instance, if the variable a contains 4 before the expression is evaluated, the value of the expression a++ is 4. As a result of evaluating the expression and its side effect, a contains 5.

x = a (value of expression is a) Example: x=a++ a = a+1(value of a is incremented by 1) Note: The operand in a postfix expression must be a variable.

Prefix Expressions: The operator comes before the operand.

Prefix increment/decrement: In C, we have only two prefix operators that form prefix expressions: prefix increment and prefix decrement. With the prefix operators, the effect takes place before th e expression that contains the operator is evaluated.

a = a +1 (value of a is incremented by 1) Example: x=++a x = a( value of expression is a after increment) if the variable a contains 4 before the expression is evaluated, after evaluation th e value of both a and x will be 5.

Unary Expressions: A unary expression, like a prefix expression, consists of one operand and one operator. The major difference is a prefix expression needs a variable while unary expression can have an expression or a variable as the operand.

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 47 Sizeof: The sizeof operator tells us the size, in bytes, of a type or a primary expression. On some PC the size of int is 2 bytes, some mainframes it is 4 bytes, and on super computers it is 16 bytes. It is important to know the ex act size of an integer; we can use the sizeof operator with

the integer type.

Note: It is also possible to find the size of primary expression.

Examples: sizeof -345.23, sizeof x; Unary plus/minus: The unary plus and unary minus are what we think of as simply the plus and minus signs. In C, however, they are actually operators. Because they are operators, they can be used to compute the arithmetic value of an operand.

Expression Contents of a Before expression Expression value +a 3 +3 -a 3 -3 +a -5 -5

-a -5 +5 Binary Expressions: These binary expressions are formed by an operand – operator - operand combination.

Examples: Any two numbers added, subtracted, multiplied or divided are usually formed in algebraic notation, which is a binary expression.

Assignment expression: The assignment expression evaluates the operand on the right side of the operator (=) and places its value in the variable on the left. The assignment expression has a value and a side effect.

 The value of the total expression is the value of the expression on the right of the assignment operator (=).

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 48  The side effect places the expression value in the variable on the left of the assignment operator.

Note: The left operand in an assignment expression must be a single variable.

Simple assignment: a = 5, b =x+1, i = i+1 The left variable must be able to receive it; that is, it must be a variable, not a constant. If the left operand cannot receive a value and we assign one to it,we get a compile error.

Compound assignment: A compou nd assignment is a shorthand notation for a simple assignment. It requires that the left operand be repeated as a part of the right expression. Five compound assignment operators are *=, +=, /=, %=, -=.

Example: x*=y+3 is evaluated as x = x*(y+3) Preceden ce and Associativity Precedence is used to determine the order in which different operators in a complex expression are evaluated. Associativity is used to determine the order in which operators with the same precedence are evaluated in a complex expression.

Precedence:

Example: 2+3*7 This expression is actually two binary expressions, with one addition and on multiplication operators. So the multiplication has the higher priority then 3*7=21 and adds the remaining 21+2=23.

Associativity: Assoc iativity can be left -to-right or right -to-left. Left -to-right associativity evaluates the expression by starting on the left and moving to the right. Right -to-left associativity evaluates the expression proceeding from right to left.

Note: Associativity is applied when we have more than one operator of the same precedence level in an expression.

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 49 Left-to-right associativity:

Example: 3 * 8 / 4 % 4 * 5 Here all these operators have the same precedence so associativity from left to right.

((((3 * 8) / 4) % 4 ) * 5) (((24/4) %4) *5) ((6%4) * 5) (2 *5) 10

Right - to-left associativity:

Example: a +=b*=c -= 5 Which is evaluated as (a+=(b*=(c -=5))) Again is expanded to (a=a+(b=b*(c=c -5))) If a=3,b=5,c=8 (a=3+(b=(5*(c=8 -5)))

then c=3,b=15,a=18.

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 50 DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 51 Side Effects: In assignment C first evaluates the expression on the right of the assignment

operator and then places the value in the left variable. Changing the value of the left variable is a side effect.

Example: x =4; This simple expression has three parts. First, on the right of the assignment operator is a primary expression that has the value 4. Second, the whole expression (x=4) also has a value of 4. And third, as a side effect, x receives the value 4.

Let’s modify the expression slight ly x = x+4; the initial value of x is 5 then x=7.

Evaluating Expressions Expressions without side effects:

Assume the value of the variables a=3,b=4,c=5 a * 4 + b /2 – c * b Following are the rules:

1. Replace the variable by their values. This gives us the following expression: 3 * 4 + 4 /2 – 5 * 4 2. Evaluate the highest precedence operators, and replace them with the resulting value.

In the above expression, the operators with the highest precedence are the multiply and divide. We therefore evaluates them first from the left and replace them with the resulting values. The expression is now (3 * 4) + (4/2) - (5*4) 12 + 2 – 20

3. Repeat step 2 until the result is obtained. Result= -6 DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 52 Expressions with side effects:

Consider the expression --a * (3+b) /2 – c ++ * b Assume the values of the variables a=3,b=4,c=5; Following are the rules:

1. Calculate the value of the parenthesized expression (3+b) - -a * 7 /2 –c ++ *b.

2. Evaluate the postfix expression(c++). Remember that as a postfix expression, the value of c++ is same as the value of c; the increment takes place after the evaluation. The expression is now - -a * 7 /2 – 5 *b.

3. Evaluates the prefix expression (- -a) Remember that as a prefix expression, the value of - -a is the value after the side effect, which means that we first decrement a and then use its decremented value.

2* 7 /2 – 5 *b 4. The multiply and division are now evaluated using their associativity rule, left to right.

The expre ssion is now 14 /3 -5 * b 7-5 *4 7-20= -13 Note: In C, if a single variable is modified more than once in an expression, the result is

undefined.

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 53 Type Conversions OR Mixed – Mode Expression An expression that contains variables and constants of different data types is called as mixed – mode expression.

There are 2 types of data conversions that take place in mixed -mode expression.

1. Implicit data conversion(Coercion) 2. Explicit data conversion(Type Casting) 1. Implicit data conversion: In this type the control will automatically convert data values of lower type are converted to the data types of higher types.

A. Implicit data conversion between integer and real values.

Example program:

main() { int r1=6,r2=4,r3; float r4=2.3,r5=3.2,r6; double r7;

r7 = (r1 * r4) + ( r2 * r5) + 10; int(6) float(2.3) int(4) float(3.2) int(10) float(6.00) float(4.00) float(10.0) float(13.800) + float(13.800) + float(10.0) float(36.600)

double(r7) (36.00000000) DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 54 printf(“ \n r7=%lf”,r7); Output: r7= 36.00000000

Rule1: when a real value is assigned to an integer variable, the fractional part of the real value is truncated and only integer part is assigned to a variable.

Rule2: when an integer value say 10 is assigned to float variable, it is stored as 10.0000.

B. Implicit data conversion between character and integer value.

Example program main() { char ch= ‘a’,op; int x=65,y;

y = ch; char(a) int(97) printf(“ \n ch=%c , y=%d”, ch , y);// Output : ch=a, y=97 op = x;

char (a) int(65) printf(“ \n x=%d, op=%c”, x, op);// Output: x=65,op=A DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 55 Rule 3: when a character is assigned to an integer variable, the ASCII value of the char is

assigned to variable.

Rule 4 : when a valid integer value (0 to 255) is assigned to char variable. Character equivalent of the integer value is assigned to a variable.

Note: Assigning an integer value into a character variable beyond its range. i.e. less than zero or greater than 255 leads to logical errors.

2. Explicit data conversion: In this type of data conversion between the output of an rvalue is forced to act as user specified data type. It refers to the process of changing an entity of one data type into another.

Syntax: lvariable=(data type) rvalue; Typecasting Example program for both ex plicit and implicit conversions main() {

int x=5, y=2; float z; z = x / y; DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 56

int(5) int(2) implicit data conversion float(2.0000) int(2) printf(“ \n %f”, z); Output: 2.0000 z =(float)x/y; float float (2.5000) explicit data conversion

printf(“ \n %f”,z);// Output: 2.5000 Statements:

A statement causes an action to be performed by the program. The C statement ends with a semicolon (;). The statement that starts with a ‘#’ symbol is an “include statement” to include header files in the program. In C there are six types of statements. They are as follows.

1. Selection statements: These types of statements are executed depending on the condition. These include if and switch.

2. Iteration statements: These statements are executed repeatedly until a condition is satisfied. These include for, while and do-while.

3. Jump statements: It alters the flow of execution. These are break, continue, goto, and return.

4. Label statement: It is used to give the location of the target statement to which control must be transferr ed. These are case, default and label.

5. Expression statement: These statements composed of valid expression are called expression statements.

6. Block statement: A block consists of a set of statements enclosed within flower braces ‘{’ and ‘}’. These are also called compound statements.

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 57 Control Structures A program is nothing but the execution of sequence of one or more instructions. Some times it is desirable to alter the execution of sequence of statements in the program depending

upon certain circumstances. This involves decision making through branching and looping .

Control statements specify the order in which the various instructions in a program are to be executed by the computer. i.e. they determine the ‘flow of control’ in a program. Vari ous control statements in C are:

 Selection or decision control statements  Case control statements  Repetition or Loop control statements Selection control statements: - Selection control statements allow the computer to take a decision as to which statement is to be executed next. Different selection control statements

are:

 if statement  Conditional operator  if statement : The if statement is a powerful decision making statement and is used to control the flow of execution of statements. It can be achieved through different forms of if statement.

a) simple if b) if – else c) nested if-else d) else -if ladder a) simple if statement: C uses the keyword “if” to execute a set of statements or one statements when the logical condition is true.

Syntax: if(condition or expression) { Statements -block; } next statement DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving

MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 58 It allows the computer to evaluate the expression first and then depending on the value of expression, the control is transfers to the particular statement. If the expression is true (non - zero value) then the statement -block is executed and next statement is executed. If the expression is false (zero), directly next statement is executed without executing the statement -

block . Statement -block may be one or more statements. If more than one statement, then keep all those statements in compound block({ }) Example:

1. if( age > 60) printf(“Old person”); 2. if( marks >100) { printf(“ Invalid marks”);

printf(“ Check your marks once again “); } DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 59 Expression

b) if –else statement : It is an extension of simple if. It takes care of both the true as well as false conditions. It has two blocks. One is for if and it is executed when the condition is true , the other block is for else and it is executed when the condition is false . No mu ltiple else statements are allowed with one if.

Syntax: if(test condition) { True block statements } else

{ False block statements } Next statement Flowchart: false (zero) true (one)

True block stmts False block stmts DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 60 If the condition is true then true block statement(s) is executed, otherwise if the condition is false, then false -block statement(s) is executed. The else cannot be used without if.

Example: if(a%2 = = 0) { Printf(“ even number”); } else

{ Printf(“odd number”); } c) Nested if -else statement : When a series of decisions are involved, we have to use more than one if -else in nested form.

Syntax: if( condition -1) { if(condition -2) { ………

if(condition -3) { Statement -1 } else

{ Statement -2 DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 61 }

} else { Statement -3 }

} else { Statement -4 }

next statement In this kind of statements, number of logical conditions is checked for executing various statements. If any condition is true then associated block will be executed, otherwise it skips and executes else block statements. We can add repetitively if statements in else block also.

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 62 Example: if(a>b) { if(a>c)

{ printf(“ ais big”); else { printf(“c is big”);

} } else { if(c>b)

{ printf(“c is big”); } else {

printf(“ b is big’); } } d) else-if ladder : The else -if ladder is used when multipath decisions are involved.

Syntax : if(condition -1) Statement -1 else if(condition -2) Statement -2 else if(condition -3)

Statement -3 ...

….

….

else Statement -x next statement DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 63

Example : if(avg>=70) printf(“ distinction”); else if(avg>=60) printf(“ first class”); else if(avg>=50)

printf(“second class”); else if(avg>=40) printf(“third class”); else printf(“fail”);

Case control statement: At times, the if condition may increases the complexity of the program when one of many alternatives is to be selected. C has built -in multiway decision statement known as switch -case . The switch statement requires only one argumen t variable or expression. It tests the value of a given variable against a list of case values and when a match is DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving

MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 64 found, a block of statements associated with that case is executed, if not such match, then default statement is executed.

Syntax : switch(var iable or expression) { case value -1: block -1 break; case value -2: block -2

break; ..

..

..

..

default: default -block } next statement The expression is an integer expression or character. Value -1, value -2 are either integer constants or character constants. These values should be unique with in a switch statement.

Case labels end with colon ( : ).

The break statement signals the end of a particular case and causes an exit from the switch statement, transferring the control to the next statement following the switch.

The default is an optional case when present. It will be executed if the value of the expression doesn’t match with any of the case values. If not present, no action takes place if all matches fail and control goes to the next statement.

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 65 Example: switch(op) { case ‘+’: c=a+b; break;

case ‘ -’: c=a -b; break; case ‘*’: c=a*b; break; case ‘/’: c=a/b;break; default: printf(“wrong option”); }

Loop control statements Many tasks are needed to be done with the help of a computer and they are repetitive in nature. Such type of actions can be easily done by using loop control statements.

Example : calculation of salary of employs of an organization for every month.

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 66 A loop is defined as a block of statements which are repeatedly executed for certain number of times to do a specific task.

Steps in loops: - 1. Loop variable: It is a variable used in loop to evaluate.

2. Initialization: It is the step in which starting value or final values are assigned to the loop variable.

3. Test -condition: It is to check the condition to terminate the loop. It is any relational expression with the help of logical operators.

4. Update statement: It is the numerical value added or subtracted to the loop variable in each round of the loop.

C language supports three types of loop control statements.

 while  do-while  for  while: This is the simplest looping structure in C. the while is an ent ry-controlled loop statement.

Syntax: initial statement while(test condition) { Statement(s) Update statement

} DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 67 Start Initialization

Condition End An action or series of actions Flow chart:

The test condition may be any expression, is evaluated and if it is true then the body of the loop is executed. The test condition is once again executed for updated values, and if it is true the body of the loop is executed once again. This process is repeated unt il the test condition is finally becomes false and control is transferred out of the loop to the next statement. The body of the loop may contain one or more statements. The braces are needed if the body of the loop

contains more than one statement.

Exampl e: main() { int i,sum; i = 1; sum=0; while (i<=10)

{ sum = sum + i ; i + +; } printf(“sum=%d”,sum);

} Here the value, sum of first ten numbers is stored into the variable sum; i is called as loop variable.

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 68 Start Initialization true Condition

false An action or series of actions The loop is repeated for ten times to do that process, each time by incrementing the value of i by one. Once the value of i becomes 11 then the test condition becomes false and the control is out of the loop.

 do-while : On some occasions it might be necessary to execute the body of the loop before the test condition is performed. Such situations can be handled by the do -while statement. Do -while id exit controlled loop statement.

Syntax:initial statement do { Statement(s) Update statement

} while (test – conditio n); next statement Flow chart :

(Post -test Loop) The body of the loop is executed first, and then at the end of the loop the test condition is evaluated, if it is true then the statements are executed once again. The process of execution continues until the test condition finally becomes false and the control is transferred to the next statement

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 69 Example :

main() { int i, sum; i =1; sum=0;

do { sum = sum + i; i + +; } while ( i<=10);

printf(“Sum=%d”, sum); }  for statement : The for loop entry controlled loop that provides a more concise loop control structure.

Syntax: for( initialization ; test-condition ; increment/decrement) { Statement(s) } next statement

The for loop allows to specify three things about the loop in a single line.

i. Setting a loop counter variable to an initial value using assignment statement. Eg:

i=1 count=0; ii. the test condition is a relational expression that determines the number of iterations desired or it determines when to exit from the loop. If the test condition is true, the body of the loop is executed, otherwise th e loop is terminated and execution continues with the next statement after the loop.

Eg: i<=10 iii. After evaluating the last statement of the body the loop, the control is transferred to the increment/decrement statement of the loop. And the new value is again tested to see whether it satisfies the loop condition or not.

Eg: i++ ++i i+=2 DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 70  The body of the loop may contain one or more statements. In case there is more than one statement then braces

 The three sections of for loop must be separated by semicolo ns (;). Initialization and incr/decr parts may contain more than one statement must be separated by commas.

Example: for(i=1, j=10 ; i<=10 ; i++, j --)  The test -condition may have any compound relation and the testing need not be limited only to the loop variable.

Example: for(i=1; i<20 && sum <100 ; i++)  It is permissible to use expressions in the assignment statement of initialization and incr/decr sections.

Example: for( k=(a+b)/2; k>0;k=k/2)  The sections of for loop my absent depends on requirement in the program. But it leads to take some extra care about those sections.

Example: for( ; ; ) This statement leads to infinite loop or never –ending process.

Nesting of loops: The way if statement can be nested, similarly whiles and for can also be nested.

Example: for(i=1;i<=3;i++) //outer for loop { for(j=1;j<=2;j++) // inner for loop { Printf(“ \t %d %d”, i,j);

} Printf(“ \n”); } Here in this example nested for loop is used, and the total process is executed for 6( 3 * 2) DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving

MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 71 times. And the output of this example will be: 1 1 1 2 2 1 2 2 3 1 3 2 The way for loops have been nested here, similarly while and do -while can also be nested. Not

only this, a for loop can occur within a while loop, or a while within a for.

Example: Comparison of three loops. Finding the sum of first 10 numbers by using all loop statements.

Program to write the sum of first 10 numbers by using while loop.

#include int main() { int i,sum; sum=0; i=1;

while(i<=10) { sum=sum+i; i++; }

printf(“Sum of first 10 numbers = %d”, sum); return 0; } Program to write the sum of first 10 numbers by using do-while loop.

#include int main() { int i,sum; sum=0;

i=1; DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 72 do {

sum=sum+i; i++; }while(i<=10); printf(“Sum of first 10 numbers = %d”, sum); return 0;

} Program to write the sum of first 10 numbers by using for loop.

#include int main() { int i,sum; for(i=1,sum=0 ;i<=10 ;i++)

{ sum=sum+i; } printf(“Sum of first 10 numbers = %d”, sum); return 0;

} Jumps in loops : We often come across some situations where we want to make a jump from one statement to other statement, jump out of a loop or to jump to next iteration of the loop instantly,. This can be accomplished by the statements like :

 break  continue  goto .

break statement:

 When we want to jump out of a loop instantly without waiting to get back to the condition test, then the keyword break allows us to do this.

 The break statement provides an early exit from the loop.

 A break is usually associated with an if.

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 73 Example:

for(i=1;i<=3;i++) { for(j=1;j<=5;j++) { if(j = = 3)

break; else print f(“ %d %d”, i, j); } printf(“ \n”);

} Output: 1 1 1 2 2 1 2 2 3 1 3 2 In this example when j value equals 5, break takes the control outside the inner for loop

only, since it is placed inside the inner loop.

The continue statement :

 When we want to take the control to the beginning of the loop by passing the statements inside the loop which are not yet been executed, then the keyword continue allows us to do this.

 It causes the next iteration of the loop to b egin and it applies only to loops.

 A continue is usually associated with an if.

Example: for(i=1;i<=2;i++) { for(j=1;j<=2;j++) { if(i = = j)

continue; else printf(“ \n%d %d”, i, j); } }

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 74 Output : 1 2 2 1 In this example when i and j values are equal, continue takes the control to the inner for loop

by ignoring rest of the statements in the inner for loop.

The goto statement :

 The goto statement alerts the normal sequence of program execution and control transfers to some other part of the program.

 The goto statement leads the control to go to the particular part of the program by indicating in its label name.

Syntax: goto label; Where label is a unique identifier used to label the target statement to which control will be transferred. The general format of the label statement is:

label : statement; Example:

void main( ) { int x; read : scanf(“%d”,&x); if(x<0)

goto read; else printf(“x=%d”,x); } Here read is label, whenever x value entered as negative(x<0) then the control goes to read

label, and once again scanf( ) statement executed to read next value.

Command Line Arguments: Arguments passed to the main function are known as Command Line Arguments. Command line arguments are given after the name of the program during the execution of the program in a command -line shell. To pass command line arguments, main() is defined with two arguments : first argument is the number of command line arguments and second is list of command -line arguments.

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 75 int main(int argc, char *argv[ ]) { ……..

}  argc (argument count) is int and stores number of command -line arguments passed by the user including the name of the program. So if we pass a value to a program, value of argc would be 2 (one for argument and one for program name)  The value of argc should be non negative .

 argv( argument vector) is array of character pointers listing all the arguments.

 If argc is greater than zero, the array elements from argv[0] to argv[argc -1] will contain pointers to strings.

 argv[0] is the name of the program , After that till argv[argc -1] every element is a command line argument .

Example:

int main(int argc, char* argv[ ]) { printf( "You have entered %d arguments ", argc ); for (int i = 0; i < argc; ++i) printf(“%s”, argv[i] );

return 0; } Properties of Command Line Arguments:

1. They are passed to main() function.

2. They are parameters/arguments supplied to the program when it is invoked.

3. They are used to control program from outside instead of hard coding those values inside the code.

4. argv[0] holds the name of the program.

5. argv[1] points to the first command line argument and argv[argc -1] points last argument.

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 76 UNIT -II Topics Covered:

Pointers – Pointer variable, pointer declaration, Initialization of pointer, Accessing variables through pointers, Pointer Arithmetic, pointers to pointers, void pointers Arrays – Definition, declaration of array, Initialization, storing values in array, Two dimensional arrays, Multi -dimensional arrays. A rrays and Pointers, Array of pointers Strings – Declaration and Initialization, String Input / Output functions, String manipulation functions,

strings and pointers, Arrays of strings Pointer: A Pointer is a variable which can store the address of another variable Syntax for declaring a Pointer dataype *var_name datatype is the pointer's base type; it must be a valid C data type and var-name is the name of the

pointer variable Example: int *p; - Pointer to an integer float *q; - Pointer to a float char *r; - Pointer to a char a. We define a pointer variable

b. assign the address of a variable to a pointer c. access the value at the address available in the pointer variable Example Program for declaring and using a Pointer #include int main( )

{ int i = 10, *p; p = &i; printf(“Value of i through pointer p : %d”, *p); return 0; } DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving

MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 77 Benefits of using pointers are a. Pointers can be used to return multiple values from a function via function arguments.

b. Pointers allow arguments to be passed by reference c. Pointers allow passing arrays and strings as arguments to functions more efficiently d. Pointers allow C to support dynamic memory management.

Null Pointer: A pointer that is assigned NULL is called a null pointer.

Example: int *p = NULL Pointer to Pointer: A variable that holds the address of another Pointer variable Syntax: datatype **var_name; Example: int **q;

Program showing the use of Pointer to Pointer #include int main( ) { int a=10, *p, **q; p=&a;

q=&p; printf(“Value of a : %d”, a); printf(“Value of a through pointer p : %d”, *p); printf(“Value of a through pointer to pointer q : %d”, **q); return 0; }

Void Pointer : A variable that can hold the address of a variable of any type Syntax: void *var_name; Example: void *p; Program showing the use of Void Pointer #include int

main( ) { int a = 10; float b = 10.5; char c = ‘A’; void *p;

p=&a; printf(“Value of a through pointer : %d”, *((int *)p)); p=&b; printf(“Value of b through pointer : %f”, *((float *)p)); p=&c; printf(“Value of c through pointer : %c”, *((char *)p)); return 0;

} DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 78 Arithmetic operations that can be performed on pointers i. Like normal variables, pointer variables can be used in expressions.

Example: x= (*p1) + (*p2); ii. C language allows us to add integers to pointers and to subtract integers from pointers Example: If p1, p2 are two pointer variables then operations such as p1+4, p2 - 2, p1 - p2 can be performed

iii. Pointers can also be compared using relational operators.

Example: p1>p2, p1==p2, p1! =p2 are valid operations iv. Pointer constants should not be used in division or multiplication. Also, two pointers cannot be added.

Example: p1/p2, p1*p2, p1/3, p1+p2 are invalid operations.

v. Pointer increments and scale factor when a pointer is incremented, its values is increased by length of data type that it points to. This length is called scale factor.

Example: If the address of p1 is 1002. After using p1=p1+1, the value becomes 1004 but not 1003.

Arrays:

C supports a derived data type known as array that can be used to handle large amounts of data (multiple values) at a time.

An array is collection of elements of the same data type , which share a common name.

Array elements are always stored in contiguous memory locations.

Each element in the group is referred by its position called index .

The first element in the array is numbered 0, so the last element is one less than the size of the array.

Before using an array its type and dimension must be declared, so that the compiler will know what kind of an array and how large an array.

Each array element is referred by specifying the array name followed by one or more subscripts, with each subscript enclosed in square brackets. The value of each subscript must be expressed as a non-DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 79 negative integer , variable or expression. The number of subscript determines the dimensionality of the

array. We can use arrays to represent not only list of values but also tables of data in two or more dimensions. We have different types of arrays based on its dimensional.

 One-dimensional arrays / Single -dimensional arrays  Two -dimensional arrays / Double -dimensional arrays  Multi -dimensional arrays One – Dimensional arrays:

A list of items can be given one variable name using only one subscript and such a variable is called one -dimensional array or single -dimensional variable.

Syntax: data -type array -name[size]; The data -type specifies the type of elements such as int, float or char. And the size indicates the maximum number of elements that can be stored in that array Eg: int a[5] ; here a is an array containing 5 integer elements.

char name[20]; here name is an array containing 20 characters.

Note: C language character strings are as simple as array of characters . And every string should be terminated by null character (‘\0’).

The computer internally reserves five storage locations for array a in the above example as follows.

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 80 These elements may be used in programs just like any other C variables. Eg:

x = a [3] + a [2]; Y= a [4] * 2; Note: C performs no bounds (array size) checking and therefore care should be exercised to ensure that the array indices are within the declared limits.

Initialization of one -dimensional arrays: After an array is declared its elements must be initialized.

Otherwise they will contain garbage values. An array can be initialized at either of the following stages.

 At compile time  At run time Compile time initialization:

We can initialize the elements of arrays in the same way as the ordinary variables when they are declared. The values in the list must and should be separated by comma.

data -type array -name [ size ] = { list of values }; Eg:

 int a [ 6 ] = { 3, 5, 23, 28, 6, 11 }; will initialize the given values to array a.

 float avg [ 5 ] = { 78.45, 65.92, 59.1 } will assign the first three elements to 78.45, 65.92 and 59.1 and the remaining two elements to zero.

 int counter [ ] = { 1, 1, 1, 1 }; here the size is optional, it may be omitted. In such cases the compiler allocates enough space for all initialized elements.

 char name[ ] = { ‘S’, ‘I’, ‘M’, ‘H’, ‘A’, ‘\0’ }; here declares the name to be an array of characters, and is initialized by the string “SIMHA” ending with the null character. A nd we can do the same thing in another way also. i.e. we can assign the entire string at a time, not an element by element as follows:

char name [ ] = “SIMHA”  intnum [ 3 ] = { 10,20,30,40,50 }; will not work. It is illegal in C. i.e. if we have more initializes DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 81 than the declared size, the compiler will produce an error.

Run time initialization: An array can be explicitly initialized at run time. At the time of execution array values can be given.

Examples:

 int a[ 10 ] ; for ( i=0; i<10; i++) scanf(“%d”,&a [ i ]);  float x [ 15 ]; for( i=0; i<15; i++)

scanf(“%f”, &x [ i ] );  char name [ 10 ]; for(i=0;i<5;i++) scanf(“%c”, &name [ i ] ); or scanf(“ %s”, name); or char name[10];

gets(name); //Example for One dimensional array – Sum of the elements of an array // Initialize the array elements at compile time #include int main() {

int i, sum=0; int a [ 10 ] = { 12, 3, 5, 43, 21, 1, 6, 8, 9, 11 }; // Array a is initialized at compile time /* finding the sum of array a */ for(i=0; i<10; i++) sum =

sum + a[ i ]; DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 82 printf(“ \n Sum of elements of array a is %d”, sum); return 0; }

//Example for One dimensional array – Sum of the elements of an array // Initialize the array elements at run time #include int main() { int a[ 10], i, n, sum=0;

printf (“Enter no.of elements :”); scanf (“%d”, &n); printf(“Enter %d elements :”,n); for(i=0; i

/* finding the sum of array a */ for(i=0; i

Two - Dimensional Arrays: C allows us to define the data in the form of table of items by using two-dimensional arrays.

Syntax: data -type array -name [ row size ] [ column size ]; Eg: int a [ 3] [ 4 ] ; Here a is two dimensional array with row size 3 and column size 4., and the total elements we can store in this array a is 12 (i.e. 3 * 4 ).

Each dimension of th e array is indexed from zero to its maximum size minus one; the first index selects the row and the second index selects the column with in that row. Two dimensional arrays are stored in memory as follows:

Examples: Representation of two dimensional array in memory DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 83 [0] [0] [0][1] [0][2] [0][3] [1] [0] [1][1] [1][2] [1][3]

[2][0] [2][1] [2][2] [2][3] Initializing Two Dimensional Arrays : Like on -dimensional arrays, two -dimensional arrays can also be initialized at compile time and runtime.

Compile time initialization:

Two -dimensional arrays may be initialized by following their declaration with a list of initial values enclosed in braces. Until and unless we initialize the array explicitly it is having some garbage values initially.

Eg:- int a [2] [3] = {3, 5, 7, 12, 22, 32} ; Here a[0][0] = 3 a[0][1] = 5 a[0][2] = 7 And a[1][0] = 12 a[1][1] = 22 a[1][2] = 32 The initialization can also be done in row by row as follows. int a [2] [3] = { { 3, 5, 7 } , {12, 22, 32 } };

We can also initialize a two dimensional array in the form of a matrix as follows: int a[2] [3] = { { 3, 5, 7 }, {12, 22, 32 } };

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 84 When the array is completely initialized with all values, explicitly we need not specify the size of the first dimension (row size). i.e Int a [ ] [ 3] = {

{ 3, 5, 7 }, {12, 22, 32 } }; if the values are missing in an initialize, they are automatically set to zero. i.e. int a [2] [3] = { { 1, 5, },

{12} }; So here the first two elements of the first row are initialized by 1 and 5 respectively, the first element of second row to 12, and all other elements to zero .

Run time Initialization: An array can be explicitly initialized at run time. Eg:

int a [2] [3] ; Int i, j; for ( i=0 ; i < 2 ; i++) // To represent row index ( i= 0,1 ) { for ( j =0 ; j < 3 ; j ++ ) // To represent column index ( j = 0,1,2)

scanf( “ %d”, & a[ i ] [ j ]); } Eg: Program to print the multiplication table for first 10 numbers up to the 10 multiples.

#include int i,j,r,c,table[ROW][COLUMN]; #define ROW 10 #define int main() { COLUMN 10

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 85 printf(" \n MULTIPLICATION TABLE \n\n"); printf("X |"); for(j=1;j<=COLUMN; j++)

printf("%5d",j); printf(" \n \n\n"); for(i=0;i

for(j=1;j<=COLUMN;j++) { c=j; table [i][j]= r*c; printf("%5d",table[i][j]);

} printf(" \n\n"); } return 0; }

In the above program the size of the array table is mentioned as ROW and COLU MN (i.e. table[ROW] [COLUMN]) where these symbolic constants having the values 10 and 10. It is always good practice to take the size of the array in terms of symbolic constants instead of directly taking the values.

Multi -Dimensional arrays:

C allows arrays of three or more dimensions. The compiler determines the exact limit.

Syntax: data -type array -name [S1][S2][S3]………[S n]; Where Si is the size of the ith dimension.

Eg: int table [3] [4] [2]; Here table is the three dimensional array containing 24 i nteger elements (i.e. 3 * 4 * 2 = 24 ).

float a [4] [2] [5] [3] a is a multidimensional array containing 120 elements.

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 86 NOTE: A three dimensional array can be represented as a series of two -dimensional arrays, and a two -dimensional array can be represented as a series of one dimensional arrays.

/* PROGRAM TO DECLARE AND INITIALIZE A MULTI -DIMENSIONAL ARRAY AT COMPILE TIME AND PRINT THE SAME */ #include void main() {

int a[3][2][3]={ { {1,1,1}, {1,1,1} }, { {2,2,2}, {2,2,2}

}, { {3,3,3}, {3,3,3} } };

inti,j,k; printf(" \n A three dimensional array is : \n"); for(i=0;i<3;i++) { for(j=0;j<2;j++)

{ for(k=0;k<3;k++) { printf(" %d",a[i][j][k]); }

printf(" \n"); } printf(" \n\n"); } return 0;

} /* PROGRAM TO DECLARE AND INITIALIZE A MULTI -DIMENSIONAL ARRAY AT RUNTIME AND PRINT THE SAME */ #include void main() { int a[5][5][5];

inti,j,k,x,y,z; printf(" \n Enter the size of a 3D array "); scanf("%d%d%d",&x,&y,&z); printf(" \n Enter values into a 3D array of size %dx%dx%d \n",x,y,z); for(i=0;i

{ for(j=0;j

for(k=0;k

} printf(" \n A three dimensional array is : \n"); for(i=0;i

{ for(k=0;k

printf(" \n"); } printf(" \n\n"); } return 0;

} Arrays and Pointers Elements of an array can be accessed through a pointer also. We can declare a pointer variable and store the address of the first element of the array in the pointer variable. All the elements of the array can be accessed through the po inter.

Example: int arr[10] = {1,2,3,4,5}; int *ptr = arr; In the above example, arr is an integer array, ptr is an integer pointer in which address of the first element of the array is stored Program to access the elements of an array through pointer

#include int main() { int arr[5] = { 1, 2, 3, 4, 5 }; // integer array int *ptr = arr; // pointer ptr storing the address of the first element of arr

for(i=0;i<5;i++) printf("%d \n", *ptr); return 0; } DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving

MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 88 Array of Pointers(Pointer arrays):

An array of pointers is an indexed set of variables in which the variables are pointers (a reference to a location in memory ).

Syntax: datatype *arr_name[ size ]; Example: int *ptr[5]; Here ptr is an array name whose elements are integer pointers Program for Array of Pointers #include int main( )

{ int a=10, b=20, c=30; int *ptr[3]; p[0]=&a; p[1]=&b; p[2]=&c;

printf(“Value of a : %d”,*p[0]); printf(“Value of b : %d”,*p[1]); printf(“Value of c : %d”,*p[2]); return 0; }

Strings A string is an array of characters. (Or) A string is a one -dimensional array of characters terminated by a null character (‘ \0’).

Eg: “INDIA” “WELCOME” Each character of the string occupies one -byte of memory. The characters of the string are stored in contiguous memory locations .

Declaration and Initialization of Strings Syntax :

char string -name [size]; Eg:

char city [20]; Character arrays (strings) may be initializing when they are declared (compile time initialization).

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 89 Eg:

 We can initialize a character array as element by element and last character should be the null character.

char city [10] = { ‘H’, ‘Y’, ‘D’, ‘E’, ‘R’, ‘A’, ‘B’, ‘A’, ‘D’, ‘ \0’ } ;  We can initialize a character array as total string at a time.

char city [10] = “HYDERABAD”;  We can initialize a character array with out specifying the size, the compiler automatically determines the size.

char city [ ] = “HYDERABAD”; The memory representation of this character array is as follows:

0 1 2 3 4 5 6 7 8 9 H Y D E R A B A D \0 3010 3011 3012 3013 3014 3015 3016 3017 3018 3019 Reading Strings: -  The input function scanf ( ) can be used with %s format specification to read a string. Eg:

char name[30]; scanf(“%s”, name);  The scanf() function to read multi word strings is doesn’t consider white spaces. It terminates the input string at first occurrence of white space. So multi word strings can’t read by using scanf() function.

Eg: char city[30]; scanf(“%s”, city); If the input string is “NEW DELHI”, then the variable city can store only “NEW”, it ignores the rest because white space is occurred after NEW.

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 90  To read multi word strings, we can use gets( ) function or getchar( ) function repeatedly. Eg:

char city[20]; gets (city); if the input string is “NEW DELHI”, then name contains total string “NEW DELHI”.

(Or) int i=0; char city[20], ch; do { ch=getchar (); name[ i

]=ch; i++; } while(ch != ‘ \n’);  C language doesn’t allow operators that work on stings directly. I.e. assignment, arithmetic, equality operator etc are doesn’t work with strings.

Eg: char s1, s2; s1 = “WELCOME” s1==s2 invalid invalid s1+s2

invalid Writing of strings to screen  The printf() function with %s specification is used to print strings to the screen. Eg:

printf(”%s”,city);  We can also specify the precision with which the array is displayed. Eg:

char name[ ] =” RADHA KRISHNA”; printf(“ %s”, name); RADHA KRISHNA printf(“ %14s”, name); RADHA KRISHNA printf(“ % 5s”, name); RADHA KRISHNA printf(“ % 14.5 s”, name); RADHA

printf(“ % -14.5 s”, name); RADHA DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 91 printf(“ % .3s”, name); RAD We can also print strings by using puts () function and putchar () function repeatedly

Eg: puts(name) OR for(i=0;name[i]!=’ \0’;i++) { putchar(name[i]);

} PROGRAM TO READ A STRING AND PRINT IT #include int main() { char ch, city[20]; int i;

printf("Enter a city name "); i=0; do { ch=getchar();

city[i]=ch; i++; }while(ch!=' \n'); i=i-1; city[i]=' \0';

printf("The city is :"); puts(city); return 0; } String handling functions

Operators can’t work with strings directly. So to manipulate strings we have a large number of string handling functions in C standard library and the responsible header file is “string.h”. Some of those functions are:

strcpy ( ), strcmp ( ), strcat ( ), strlen ( ), strrev ( ) etc.

strcpy( ): It is to copy one string into another, and it returns the resultant string.

Syntax: strcpy( string1, string2); String2 is copied into string1.

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 92 Eg: char city1[10] = “HYDERABAD”; char city2[12] = “BANGLORE”; strcpy (city1, city2);

Here city2 is copied into city1. So city1= “BANGLORE” and city2=”BANGLORE”. The size of the array city1 should be large enough to receive the content s of city2.

strcmp( ): It is to compare two strings to check their equality. If they are equal it returns zero, otherwise it returns the numeric difference between the first non matching characters in the strings.

(i.e. +ve if first one is greater, -ve if first one is lesser).

Syntax: strcmp (string1, string2); Eg: char city1[10] = “HYDERABAD”; char city2[12] = “BANGLORE”; strcpy (city1, city2); Here city1 and city 2 are compared, and returns the numeric difference between ASCII value of ‘H’ and

ASCII value of ‘B’ as they are not equal.

Strcmp(“RAM”,ROM”); It returns some –ve value.

Strcmp(“RAM”,RAM”): It returns 0 as they are equal.

strcat ( ): This function is used to join two strings together, and it returns the resultant string.

Syntax: strcat( string1, string2); String1 is appended with string2 by removing the null character of string1 and string2 remains unchanged. The resultant string is stored in string1.

Eg: char city1[10] = “HELLO”; char city2[12] = “WORLD”; strcat (city1, city2); Here city2 is appended to city1. So city1= “HELLOWORLD” and city2=”WORLD”.

strlen( ): It is to find out the length of the given string and it returns an integer value, that is the number of characters in the given string. It takes only one parameter DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 93 Syntax: strlen( string1); It gives

the length of string1.

Eg: char city[10] = “HYDERABAD”; strlen (city); it gives the value 9.

strrev ( ): This function is to find out the reverse of a given string.

Syntax : strrev (string); Eg: char city[10] = “HYDERABAD”; strrev (city); it give the string “DABAREDYH” Strings and Pointers

A pointer can be used to access the individual elements of a String.

For Example char str[10]; declares a string str. The variable name of the string str holds the address of the first element of the array i.e., it points at the starting memory address.

So, we can create a character pointer ptr and store the address of the string str variable in it. This way, ptr will point at the string str.

char *ptr= str; In the following code we are assigning the address of the string str to the pointer ptr. #include int main() { char str[6] = "Hello"; // string variable

char *ptr = str; // pointer variable points to the first address of the string // print the contents of the string using pointer while(*ptr!=' \0') DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 94

{ printf("%c", *ptr); ptr++; // increment ptr so that it points to the next element of the string } return 0;

} Array of Strings We have array of integers, array of floating point numbers, etc..similarly we have array of strings also.

Collection of strings is represented using array of strings.

Declaration:

Char arr[row][col]; where, arr - name of the array row - represents number of strings col - represents size of each string Initialization: -

chararr[row][col] = { list of strings }; Example: - char city[5][10] = { “DELHI”, “CHENNAI”, “BANGALORE”, “HYDERABAD”, “MUMBAI” }; D E L H I \0

C H E N N A I \0 B A N G A L O R E \0 H Y D E R A B A D \0 M U M B A I \0 DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving

MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 95 In the above storage representation memory is wasted due to the fixed length for all strings #include int main() {

int i; char ch_arr[3][10] = { "spike", "tom", "jerry" };

for(i = 0; i < 3; i++) { printf("string = %s \n", ch_arr[i]); } return 0;

} DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 96 UNIT -III Topics Covered:

Designing Structured Programs using Functions - Types of Functions - user defined functions, Standard Functions, Categories of functions, Parameter Passing techniques, Scope – Local Vs Global, Storage classes, Recursive functions.

Passing arrays as parameters to functions, Pointers to functions, Dynamic Memory allocation DESIGNING STRUCTURED PROGRAMMMES In the preceding chapters, we used only the three non -derived types, void, integral, and floating –point. These are used to solve only the limited amount of problems. There are six derived data types in C: Array, Functions, Pointer, Structure, Union, and Enumerated. Breaking a complex problem into

smaller parts (understandable parts). We call each of these parts of a program a module and the process of subdividing a problem into manageable parts top-down design. In the principle of top -down design and structured programming, a program is subjected to factoring, that is the program is divided into main module and its related modules. Each module is in turn divided into sub modules until the resulting modules cannot be further subdivided. A C prog ram finds itself in a similar fashion as in top -

down structured designing. It cannot handle all the tasks by itself. Instead it requests other program -like entities – called functions .

Function: Definition A function is a self -contained block of one or more statements that perform a particular task.

Every C program can be thought of as a collection of these functions, and one of which must be main ( ) function.

The execution of the program always starts and ends with main function and main function can call other functions. A called function can receive control from a calling function , when the called function completes its execution it returns the control back t o the calling function. The communication between calling function and called function is by passing parameters at the time of calling.

Advantages of functions in C DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 97  It facilitates top -down modular programming; here the problem can be factored into unders tandable and manageable steps.

 Reusing of the code: The length of the source program can be reduced by using functions at appropriate places. i.e writing functions avoids rewriting of same code over and over.

 Using functions it becomes easier to write programs and keep track of what they are doing.

 The functions are much easier to understand and test.

 C comes with rich and valuable set of library functions that makes programmer’s work easier.

C functions can be classified into two categories.

 Library functions  User -defined functions Library functions : The library functions are predefined set of functions. The user can only use these functions but can’t change or modify them. These functions are already defined, tested and debugged in C standard library . When the user needs to use library functions, then a call to these functions is

required.

Eg: The basic input and output functions like printf( ) , scanf( ) are defined in the C library header file stdio.h.

sqrt( ), sin( ), cos( ), tan( ), pow( ), getchar( ), exit( ), toupper( ), strcmp( ), strlen( ) etc., all these are some C library functions.

User -defined functions : These are defined by the user according to the requirement in the application.

The user can modify and can create any number of func tions based on requirement. The user can certainly understand the internal working of the function.

The difference between library functions and user -defined functions  The library functions are not required to written by the user, where as user -defined fu nctions have to develop by the user at the time of writing of application.

 The user can’t modify the meaning of the library functions. But user can modify the user -defined functions.

 The library functions are already tested and debugged, but the user -defin ed functions need to be test and debug.

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 98 The structure of user -defined function:

Syntax: return -type function -name (arguments list) argument declaration { Local variable declarations Executable statement ……

…… …… return (expression or value) }  In function structure all parts not essential, it is based on the requirement of the program and

some sections or parts may be absent.

 Return -type is any data type  All functions by default return int type data.

 Function -name can be any name like variables whi ch follows naming conventions of identifiers.

 The arguments list and its associated declaration are optional. These are any valid variable name separated by commas. There may be any number of variables, any type of variables with respect to the function ca lling statement and these variables receive values from calling function.

 The declaration of local variables is required only when any local variables are used in the function.

 A function can have any number of executable statements.

 The return is a keyword which is followed by some expression or value. The return statement returns a value to the calling function and is optional. When there is no return statement, then no value is being returned to the calling function. We can return only one val ue at a time .

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 99 Eg: int add( int x, int y) int add(x,y) int add( int x, int y) { int x, y; { int z; ( or ) { (or) return ( x + y );

z = x + y; int z; } return z; z = x + y; } return z; }  Every user -defined function can have its declaration (also called as function prototyping ) and

definition. Some other function can call this function.

 When function calling statement is invoked, the control is transferred to the function definition.

It is then executed and the control is transferred back to the calling function to execute next statement.

 Any function can call any other function and can call itself (recursion).

 A function can call any number of times.

 C permits nesting of functions. Main can call function -1, which calls function -2, which calls function -3 and so on.

Actual arguments and formal arguments:

 The arguments (parameters) of function calling statement are actual arguments; the arguments of called function are formal arguments.

 The ac tual and formal arguments should match in number, type and order.

 The formal arguments receive values from actual arguments when a function is calling, and by this a communication between calling function and called function is made.

 When a function call is made, only a copy of the values of actual arguments is passed into the called function’s formal arguments.

 The values of the actual arguments must be assigned before the function call is made.

 The formal arguments must be valid variable names, but the a ctual arguments may be variable names, expressions, or constants.

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 100 Eg: //program for addition of two numbers #include int main()

{ int a, b, c; int add(int, int); // function declaration or prototyping printf(“Enter two values “); scanf(“%d%d”, &a, &b);

c = add(a,b); //function calling statement printf(“ addition of a, b is %d”, c); return 0; } int add( int x, int y) // add function definition

{ int z; z = x + y; return z; } In the above program:

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 101  a, b are actual arguments  x, y are formal arguments  main( ) is calling function.

 add( ) is called function The values of a, b are passed into x, y respectively when function is invoked and a, b values remains same.

The return statement :-  Functions uses return statement to return a value to the calling function. And exit from the called function is done by the return statement.

 The return statement returns only one value at a time. There may be more than one return statement in a function, but it returns only one value.

 The value re turned by the called function is collected by the calling function.

 Return statement with out any value will return value one. Eg:

return; this returns 1 to the calling function  Absence of return statement indicates that no value is returned, such functions return type is void (i.e returning nothing).

Eg; return; return (9*3); return (a + b); return c; Function prototype:

 Function prototyping is nothing but function declaration; it consists of function’s return type, name, and arguments list with type.

 When a function is defined, the function header in the definition must be same like its prototype declaration.

 The function prototype statement is terminated by semicolon.

 A prototype statement helps the compiler to check the return type and argument s type of the function.

 The prototype of library functions is given in the respective header files, those we include by using #include preprocessor directive.

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 102 Eg: int add( int, int); void display(char c); float average(float, float, float); Category of functions : A function depending on whether the arguments are present or not, and a value is returned or not may belong to one of the following categories.

1. Functions without arguments and without return values .

2. Functions with arguments and without return values .

3. Functions without arguments and with return values .

4. Functions with arguments and with return values .

1. Functions without arguments and without return values:

 When a function has no arguments, it does not receive any data from calling function.

 When a function does not return any value, the calling function doesn’t receive any data from called function.

 There is no data transfer in between the calling function and called function.

 This type of functions may be useful to print some messages, draw a set of lines, etc.

Eg: #include displayline(); message (); int main( ) {

displayline( ); message( ); displayline( ); return 0; }

displayline ( ) // no arguments and no return type for display line { int i; for(i=1; i<=80; i++) printf(“ -“);

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 103 printf(“ \n”); } message( )

{ printf(“ ** TRY TO UNDERSTAND THE LANGUAGE **** \n ”); printf(“ ***NOT TO BYHARD THE LANGUAGE ***** \n ”); } OUTPUT: -

** TRY TO UNDERSTAND THE LANGUAGE **** ***NOT TO BYHARD THE LANGUAGE ***** - 2. Functions with arguments and without return values:

 The nature of data communication between the calling function and the called function is with arguments but no return values.

 One-way data communication between calling function and called function through arguments.

 The control is transferred to the called function by passing some arguments, after performing the task; the control is back to the calling function without returning any value.

Eg: #include displayline(char); message (char); int main( ) {

char name[30] = “DENNIS RITCHIE”; char ch = ‘ -’; displayline( ch); message( name); displayline( ch);

return 0; } DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 104 displayline (char x ) // with arguments and no return type for displayline

{ int i; for(i=1; i<=80; i++) printf(“%c”, x); printf(“ \n”);

} message( char str[30]) // with arguments and no return type { printf(“ \t \t”); printf(“ %s”, str);

printf(“ \n”); } OUTPUT: - DENNIS RITCHIE -

3. Functions without arguments and with return values:

 The function is called without passing any arguments, but after performing the task, it returns some value to the calling function.

 One-way data communication between calling function and called function through return statement.

 The control is transferred to the called function without passing any arguments, after performing the task; the control is back to the calling function by passing some value.

Eg: #include int factorial(); int main( ) { int f;

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 105 f = factorial( ); printf(“ \n Factorial f = %d”, f); return 0; }

int factorial( ) // without arguments, but returns some value.

{ int i, f =1,n; printf(“ enter a value “); scanf(“%d”, &n); for(i=1; i<=n; i++) f= f * i ; return f;

} OUTPUT: - enter a value 4 Factorial f = 24 4. Functions with arguments and with return values: -  Two -way data communication between calling function and called function is by passing

arguments and sending back some value.

 The control is transferred to the called function by passing some arguments, after performing the task; the control is back to the calling function by returning some value.

 At the time of function calling the actual arguments are dumped into formal arguments.

Eg: #include int factorial (int x); int main( ) { int n, f; int factorial(int); // function declaration or prototyping printf(“

enter a value “); scanf(“%d”, &n); f = factorial (n); // function calling statement printf(“ \n Factorial f = %d”, f); DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving

MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 106 return 0; } int factorial( int x) // function definition with argument, with return value.

{ int i, f =1; for(i=1; i<=x; i++) f= f * i; return f; }

Parameter passing techniques:

Parameter passing is a technique used to pass data to a function. Data are passed to a function using one of two techniques: pass by value (call by value ) and pass by reference (call by reference ).

1. Call by value:

 In call by value mechanism a copy of the data is sent to the function. That is the values of actual arguments are being copied into formal arguments. And ensures that the original data in the calling function cannot be changed.

 Memory is allocated temporar ily for formal parameters and local variables.

 Whatever the modifications are done for formal parameters will not affect the actual parameters.

2. Call by Reference:

 In call by reference mechanism the address of the data rather than a copy is sent to the function. That is the address of actual arguments is being passed into formal arguments. The called function can change the original data in the calling function.

 When we pass the addresses, the receiving parameters should be pointers to hold these addresses.

 Whatever the modifications are done for formal parameters will directly affect the actual parameters.

 C language does not have a true call by reference and it is stimulated by call by address.

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 107 Eg:// program for call by value mechanism #include int main( )

{ int a, b; void swap(int, int);// function declaration or prototyping printf(“ enter two values “); scanf(“%d %d”, &a, &b);

swap(a, b); // function calling statement printf(“ Values after swap function call are: “); printf(“ a= %d \t b = %d ”, a, b); return 0; }

void swap( int x, int y) // function definition .

{ int temp; temp = x; x = y; y = temp;

} OUTPUT: - enter two values 10 20 Values after swap function call are: a = 10 b=20 Here the copy of the actual data a, b is sent to formal parameters of swap function, in swap function these are swapped but the changes made to x, y are not affect the values of a, b in main function.

Beca use the copy the data is sent but not original location.

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 108 Eg: // program for call by reference mechanism #include int main( )

{ int a, b; void swap(int, int); // function declaration or prototyping printf(“ enter two values “); scanf(“%d %d”, &a, &b);

swap(&a, &b); // function calling statement printf(“ Values after swap function call are: “); printf(“ a= %d \t b = %d ”, a, b); return 0; }

void swap( int *x, int *y) // function definition .

{ int temp; temp = *x; *x = *y; *y = temp;

} OUTPUT: - enter two values 10 20 Values after swap function call are: a=20 b=10 Here the address of the actual data (&a, &b) is sent to formal parameters ( *x, *y) of swap function, in swap function instead of creating temporary memory locations for x and y, the same memory locations

of a, b referenced by x, y. So changes made to x, y are directly affects a, b in main function. So finally swapped values are stored in a, b .

Scope - Local and Global variables A scope in any programming is a region of the p rogram where a defined variable can have its DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 109 existence and beyond that variable it cannot be accessed.

There are three places where variables can be declared in C programming language −  Inside a function or a block which is called local variables.

 Outside of all functions which is called global variables.

 In the definition of function parameters which are called formal parameters.

Local Variables Variables that are declared inside a function or block are called local variables. They can be used on ly by statements that are inside that function or block of code. Local variables are not known to functions outside their own.

The following example shows how local variables are used. Here all the variables a, b, and c are local to main() function.

Global Variables Global variables are defined outside a function, usually on top of the program. Global variables hold their values throughout the lifetime of your program and they can be accessed inside any of the functions defined for the program.

A global variable can be accessed by any function. That is, a global variable is available for use throughout your entire program after its declaration.

The following program show how global variables are used in a program. #include int main () { /* local variable declaration */ int a, b; int c;

/* actual initialization */ a = 10; b = 20; c = a + b; printf ("value of a = %d, b = %d and c = %d \n", a, b,

c); return 0; } DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 110 A program can have same name for local and global variables but the value of local variable inside a

function will take preference When the above code is compiled and executed, it produces the following result − value of g = 10 Formal Parameters Formal parameters, are treated as local variables with -in a function and they take precedence over global variables

#include /* global variable declaration */ int g; int main () { /* local variable declaration */

int a, b; /* actual initialization */ a = 10; b = 20; g = a + b;

printf ("value of a = %d, b = %d and g = %d \n", a, b, g); return 0; } #include /* global variable declaration */

int g = 20; int main () { /* local variable declaration */ int g = 10; printf ("value of g = %d \n", g);

return 0; } DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 111 Storage classes in C:

All the variables in C, not only to have a data type, they also have a “ Storage classes”. The storage class of variable tells the compiler that:

(a) The storage area of the variable : there are basically two kinds of locations in a computer where such variables or values to be kept, “ Memory and CPU Registers. The storage class of a variable determines in which of these two locations the value is stored.

(b) The initial value of the variable if not initialized (c) The scope of the variable(active) that in which functions the value of the variable would be available.

(d) Life of the variable(alive) that is how long the variable would be active or exist in the program, i.e the longevity of the variable.

There are four storage classes in C:

1. Automatic variables.

2. Register variables.

3. Static variables.

4. External variables.

1. Automatic storage classes variables: The features of automatic storage classes variables are :

Storage : Memory Initial value: Garbage value or unpredictable value.

Scope : Local to the block in which it is defined.

Life time : Until end of function or end of block where it is defined.

1. Automatic variables are declared inside a function in which they are to be utilized. They are created when the function is called and destroyed automatically when the functio n is exited.

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 112 2. Automatic variables are local to the function.

3. We use the keyword auto to declare automatic storage classes.

4. The default storage class of a variable is automatic storage class. Ex: int x ; it implies that auto int x; 5. Because of the scope of the automatic variables, they are also referred to local or internal variables.

Ex: 1. main ( ) { auto int i; int j; printf (“ \n %d \t %d”, i, j); }

Output : some garbage values, because they are not initialized to any value. A variable j without having any storage class is by default automatic. So both i, j are automatic variable.

Ex: 2. main ( ) { auto int a = 1; { auto int a = 2;

{ auto int a = 3; printf(“a = %d”, a); } printf(“ \n a = %d”, a);

} printf(“ \n a = %d”, a ); } Output: 3 2

1 DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 113 2. Register variables:

The features of a variable defined to be of Register storage class are:

Storage : Registers Initial value : Garbage value or unpredictable value.

Scope : Local to the block in which it is defined.

Life time : Until end of function or block.

1. A variable stored in CPU Register can always be accessed faster than the one which is stored in memory.

2. If a variable is used at many placed in a program, then it is better to declare it as register variable. Ex: - loop counter variables.

3. We can use the keyword “ register” to declare register variables.

4. We cannot use register class for all types of variables, because CPU registers in a micro computer are usually 16 - bit registers and therefore cannot hold a float value or a double value which require 4 and 8 bytes respectively. However C will automatically convert register variables into non register variables once the limit is reached.

Ex:- main ( ) { register int i; for(i = 1; i < = 10; i++) printf(“ \n %d”, i);

} . Static variables: The features of static storage class variable are:

Storage : Memory Initial value : Zero Scope : Global (may be internal static or external static) Life time : Value of the variable persists between different function call.

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 114 1. Static variables persist until the end of the program.

2. A static variable may be either an initial type or an external type, depending on the place of declaration.

3. We can use the keyword “static” to declare a variable as static variable.

4. A static variable is initialized only once.

5. The difference between auto variables and static variables don’t disappear when the function is no longer active. These values persist, but auto variables disappear when the function is no longer active.

Ex:- main ( ) { int i; for(i = 1; i < = 3; i++) Display ( );

} Display ( ) { static int x = 0; x = x +1; printf(“x = %d \n”, x);

} Output: - x = 1 x = 2 x = 3 4. External variables: - The features of a variable whose storage class has been defined as external

are as follows:

Storage : Memory Initial value : Zero Scope : Global Life time : As long as the program’s execution doesn’t come to an end.

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 115 1. External variables are declared outside of the all functions.

2. The external variables are both alive and active throughout the entire program.

3. They may be declared using the keyword “extern”.

4. The external variables are also known as global variables. These variables can be accessed by any function in the program.

5. In case, both external and auto variables are declared with the same name, in a program the first priority is given to the auto variable.

6. Use external storage class only these variables which are being used by almost all the functions in the progr am. This would avoid unnecessary passing of the variables as arguments when making a function call.

Ex:- int i = 10; main ( ) { int i = 20; printf(“ \n %d”, i);

display ( ); { printf (“ \n %d”, i) } Output : 20

10 Recursion:

 When a function calls itself , then that process is called as recursion and that function is called as recursive function.

 Recursive functions can be used to solve problems where the solution is expressed in terms of successively applying the sa me solution to subsets of the problems.

 Every recursive functions must has to have two basic properties:

( i ) A termination condition called anchor step (usually if statement) to avoid infinite process.

( ii ) A repetition statement called recurrence step to repeat the function calling process.

 Recursion is of two types. Direct recursion and indirect recursion .

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 116  When a function calls itself, then it is direct recursion . But when function -1 calls function -2 and in turn function -2 calls function -1 then it is indirect recursion .

Eg: To calculate the factorial value of number 4, the recursion process is as follows.

int main( ) { int n, f; int factorial(int); // function declaration or prototyping n = 4;

f = factorial (n); // function calling statement printf(“ \n Factorial f = %d”, f); return 0; } int factorial( int x) //function definition with argument, with return value.

{ int f; if( (x = = 1) || (x = = 0)) return 1; else

return ( x * factorial ( x - 1) ); } Anchor step: if( (x = = 1) || (x = = 0)) Recurrence step: return ( x * factorial ( x - 1) ) x * factorial ( x - 1) is processed as follows:

4 * factorial( 3 ) 3 * factorial ( 2 ) 2 * factorial ( 1 ) DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 117

1 4 * 3 * 2 * 1 = 24 Passing Arrays as a parameter to a function An array can be passed as a parameter to a function.

Syntax: return type function_name( datatype *array_pointer); or return type function_name( datatype array_name[size]); Example: void sum(int *a); Where a is a formal parameter which holds the starting address of the array passed as a

parameter to the function sum Or void sum( int a[10]); Program for passing an array as argument to a function #include

void sum(int *a, int n); int main( ) { int a[10], i, n; printf(“Enter the size of the array”);

scanf(“%d”, &n); printf(“Enter %d elements”,n); for(i=0; i

void sum(int *a, int n) { int i, sum = 0; for(i=0; i

printf(“Sum : %d”, sum); } DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 118 Pointers to Functions

A function, like a variable has a type and address location in the memory. It is therefore possible to declare a pointer to a function, which can the n be used as an argument in another function .

A pointer to a function can be declared as follows.

Syntax: datatype (*fptr)(); fptr is a pointer to a function which returns type value A function pointer can be made to point to a specific function by assigning the name of the function to the pointer Example:

int multiply(int a, int b); function declaration int (*fptr)(int, int); pointer to a function fptr = multiply; assigning address of multiply to fptr n=(*fptr)(a,b); function call using pointer fptr Program showing Pointer to a Function

#include int multiply(int a, int b); { return a * b; }

int main( ) { int a, b, c; int (*fptr)(int,int); printf(“Enter two numbers”); scanf(“%d%d”,&a,&b);

fptr = multiply; c = (*fptr)(a,b); printf(“Result : %d”,c); } DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving

MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 119 Dynamic Memory Management Dynamic allocation : Dynamic memory allocation is the process of allocating memory during execution time.

Dynamic Memory Allocation Functions in C:

This allocation technique uses predefined functions to allocate and release memory for data during execution time.

Function Syntax malloc () Void * malloc (size_t); calloc () Void * calloc (int number, size_t ); realloc () Void * realloc (pointer_name, size_t); free () free (pointer_name);

1. malloc( ) :

 malloc( ) function is used to allocate space in memory during the execution of the program.

 It does not initialize the memory allocated during execution.

 It carries garbage value.

 It returns null pointer if it couldn’t be able to allocate requested amount of memory.

2. calloc( ) : calloc( ) function is also like malloc( ), but calloc( ) initializes the allocated memory to zero.

3. realloc( ) :

 realloc ( ) function modifies the allocated memory size by malloc( ) and calloc( ) functions to new size.

 If enough space doesn’t exist in memory of current block to extend, new block is allocated for the full size of reallocation, then copies the existing data to new block and then frees the old block.

4. free ( ) :

free ( ) function frees the allocated memory by malloc ( ) and calloc ( ) functions and returns the memory to the system DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 120 Example:

Program to allocate memory for an array dynamically, store and access its values #include #include int main( ) {

int *a, i, n; printf(“Enter the size of the array”); scanf(“%d”,&n); a = (int *) calloc(n , sizeof(int)); printf(“Enter %d elements into the array”);

for(i=0; i

free(a); } Difference between static memory allocation and dynamic memory allocation Static Memory Allocation Dynamic Memory Allocation It is the process of allocating memory at

compile time. It is the process of allocating memory during execution of program Fixed number of bytes will be allocated Memory is allocated as and when it is needed.

The memory is allocated in memory stack The memory is allocated from free memory pool (heap).

Execution is faster Execution slow Memory is allocated either in stack area or data area Memory is allocated only in heap area Ex: Arrays Ex: Dynamic arrays, Linked List, Trees DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving

MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 121 UNIT – IV Topics going to covered:

Structures and Unions - Declaration, initialization, accessing structures, operations on structures, structures containing arrays, structures containing pointers, nested structures, self referential structures, arrays of structures, structures and functions, pointers to Structures , unions.

Structure is a mechanism for packing data of different types. It is a convenient tool for handling a group of logically related data items. Simply the structure is a collection of logically related elements of different data types.

Eg: It can be used to represent a set of attributes, such as student -name, roll -number, and marks. We use a structure to represent all these different data elements.

Declaration of a structure : A structure is declared as follows:

Syntax : struct tag-name { Data type member -1; Dat type member -2; :

:

Data type member -n; }; Eg: struct student DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 122

{ int rno; char name[20]; int tm; flaot avg;

};  Here “struct” is a keyword used to declare a structure.

 Tag-name is the name given to structure declared.

 Member -1, member -2,….member -n are elements or fields of the structure, each member may belong to different data type.

 Structure declaration should be terminated by semicolon.

 Structure declaration doesn’t get any space for its members, it simply describes a format called template to represent the information.

 Memory allocated only after declaring structure variables.

 Structure variables can be declared using tag -name as follows:

Syntax: struct tag -name variable -1, variable -2, variable -N; Eg: struct student s1, s2, s3; Here student is a structure and it is having 4 different members which are logically related. And s1, s2 and s3 are three structure variables.

 It is also allowed to combine both the template declaration and structure variables declaration in one statement. The declaration is as follows:

struct student { int rno; char name[20]; int tm;

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 123 flaot avg; }s1,s2;  Tag-name is optional in structure declaration. When tag -name is absent then structure variables should be

created in structure declaration itself, before semicolon.

Eg: struct { int rno; char name[20]; int tm;

flaot avg; } s1, s2;  Individual members of the structure cannot be initialized within structure declaration.

struct student { int rno = 28; char name[20] = “SUN”; Invalid int tm = 500;

flaot avg = 90; }; Accessing the members of the structure:

Members of the structure can be accessed by writing structure variable name with member selection operator (dot operator . ) and member name.

structure variable . member; Eg:

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 124 s1. rno = 28; s1 .

tm = 500; Structure Initialization :

Like any other data type, a structure variable can be initialized. We can initialize a structure at compile time and also we can initialize the structure members at run time.

 Compile time initialization: One way to initialize structure members is direct initialization.

struct student s1 = { 28, “ SUN”, 500, 90 }; Here, when initializing the structure directly like above, and then the order should be maintained. That is the order of assigning values is same as the order of members declared in the structure .

 And other way to initialize the structure members as follows:

struct student s1; s1.rno = 28; strcpy (s1.name,”SUN”); s1.tm= 500; s1.avg = 90;

 we can initialize structure members at run time by considering the scanf statement as follows: scanf (“%d%s%d%f”, &s1.rno, s1.name, &s1.tm, &s1,avg); /* Example for structure declaration and initialization */ #include struct student

{ int rno; char name[20]; int tm; float avg;

}; DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 125 void main() {

struct student s1 = { 28,"SUN",450,89}; clrscr(); printf(" \n Roll Number : %d",s1.rno); printf(" \n Name : %s",s1.name); printf(" \n Total : %d",s1.tm);

printf(" \n Average: %f", s1.avg); getch(); } Output: - Roll Number: 28 Name:

SUN Total: 450 Average: 89.000000 Comparison and Copying of structure variables :

 We can copy one structure variable into another; it can be achieved by copying individual members or entire structure at a time by using assignment statement.

Eg: struct student s1, s2; s2 = s1;  Comparison of structure variables for their equality and inequality purpose by using equality operator (= =), and inequality operator (!=) is not allowed in all compilers. If it is necessary to compare two structure variables then it is to follow individual structure member’s comparison Arrays of structures

 We can declare an array of structures, each element of the array representing a structure variable. Eg: The total marks and average marks analysis of the marks report obtained by a class of 60 students is as follow:

struct student s[60]; Here s is an array of 60 elements to the structure student, or simply s is an array of structures.

 Array of structures allowed us to create an array of similar type of elements which themselves are a collection of dissimilar data type.

In an array of struc tures all elements of the array are stored in adjacent memory locations Eg /* Calculating the total marks of 3 students */ DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 126 struct marks

{ int m1; int m2; int m3; int m4;

}; int main( ) { int sum=0, i; struct marks s[3] = { {56,67,78,59}, {60,50,70,80}, {52,62,72,82} };

for(i=0;i<3;i++) { sum=0; sum = sum + s[i].m1 + s[i].m2 + s[i].m3 + s[i].m4; printf(“ \n Total marks of %d = %d”, s[i], sum);

} return 0; } Arrays within structure C language allows us to use arrays as structure members. We can use arrays as structure members as

single dimensional or multi dimensional arrays, or array of characters.

Eg:- struct student { char name[20]; int rno; DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving

MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 127 int m[4]; int tm; }; Here the structure members name and m are arrays, where name is character array and m is integer

array. The variable name contains 20 elements. And m contains 3 elements m[0],m[1],and m[2], these represent marks obtained by a student in 3 subjects. These elements can be accessed using appropriate subscripts.

/* Program to read student name, roll number and marks in 5 subjects and calculate total marks and average marks obtained by 3 students using array of structures and arrays with in structures */ struct student { char sname[20];

int rno; int m[5]; int tm; float avg; }s[3];

int main() { int i,j,t; for(i=0;i<3;i++) {

printf(" \n Enter %d student details \n ",i+1); printf(" \n enter student name and roll number "); scanf("%s%d",s[i].sname, &s[i].rno); printf(" \n Enter marks in 5 subjects "); for(j=0;j<5;j++)

{ scanf("%d",&s[i].m[j]); DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 128 }

} for(i=0;i<3;i++) { t=0; for(j=0;j<3;j++)

{ t=t+s[i].m[j]; } s[i].tm=t; s[i].avg=s[i].tm/5;

} printf(" \n Students details are \n"); for(i=0;i<3;i++) { printf(" \n Name: %s", s[i].sname);

printf(" \n Number : %d",s[i].rno); printf(" \n Total : %d",s[i].tm); printf(" \n Average : %f", s[i].avg); } return 0;

} Structures and Pointers:

 Pointer as a structure variable  Pointers within structures Pointer is a variable that holds address of another data variable. We can also define pointer to structure.

That is we can declare a pointer as a structure variable. Here starting address of the structure member variables can be accessed to pointer variable of he same structure.

Eg: struct book { char name[20]; char author[20]; int pages;

}; DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 129 struct book *ptr; Here ptr is a pointer variable to the structure book. We can access the members of the structure by

using ptr variable and is accomplished by indirect member selector operator ( ->) or struc ture pointer operator.

i,e ptr ->name, ptr ->author, ptr ->pages.

/*Example for pointer to structure*/ struct book { char name[20]; char author[20];

int pages; }; int main() { struct book b1 = {“let us c”,”kanetkar”,100};

struct book *ptr; ptr=&b1; printf(“ \n%s by %s of %d pages”,b1.name,b1.author,b1.pages); printf(“” \n %s by %s of %d pages”, ptr ->name, ptr ->author, ptr ->pages); return 0 ;

} In the above example ptr is a variable, which is used to hold the address of structure variable. The structure members can be accessed using the indirect selector operator.

*ptr -> rno is same as (*ptr).rno.

The parenthesis around *ptr are necessary, because the member operator, has a higher precedence than the operator “*”.

Pointer as structure member:

We can take pointer as a structure member. We can access these members through structure variable DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 130 Eg: /*Pointer as structure member*/ int main()

{ int a=21, h=5.40; struct boy { char *name;

int *age; float *height; }; struct boy b,*ptr; strcpy(b.name,”SUN”);

b.age=&a; b.height=&h; printf(“ \n Name :%s”,b.name); printf(“ \n Age :%d”,*b.age); printf(“ \nHeight :%d”,*b.height);

ptr=&b; printf(“ \n through pointer, accessing the structure variable”); printf(“ \n Name :%s”,ptr ->name); printf (“\n age :%d”,*ptr ->age); printf(“ \nHeight :%f”,*ptr ->height);

return 0; } Here b and *ptr are also two structure variables. The members of structure variable boy are pointers.

The pointer *ptr is pointer to structure boy, We can access members of struct ure boy through b and ptr, and by using direct selector ( .), indirect selector ( ->). The members can be accessed through the variable b is as follows:

b.name *b.age *b.height; The members can be accessed through the variable ptr is as follows.

ptr->name, *ptr->age, *ptr->height.

If p is a structure variable and age is a member of the structure then the following are different notations to access the member in different ways.

p . age : when both p and age are ordinary variables (use direct member selector .) DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 131 p -> age : when p is a pointer to the structure and age is ordinary member of the structure( use indirect member selector ->).

*p . age : when p is ordinary variable to structure and age is a pointer member of the structure.

*p -> age : when both p and age are pointer variables Structures and Functions:

Like variables of standard data type, structure variables can also be passed to the function by value or address. Whenever a structure element is passed to declare the structure variable outside the main() function i.e. global.

 We can pass individual elements of a structure variable as parameters to functions  We can pass an entire structure as an argument.

 We can also pass address of the structure as an argument to a function.

i) Passing members of a structure as arguments to a function.

struct boy { char name[20]; int age; int wt;

}; struct boy b1={“amit”,20,45}; main() { display(b1.name,b1.age,b1.wt);

} display(char s[20],int a,int w) { printf(“ \n Name :%s”,s); printf(“ \n Age :%d”,a);

printf(“ \n weight :%d”,w); } DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 132 In the above example, individual elements of structure boy (members of structure) are passed as

arguments to the function display(). b1.name, b1.age, b1.wt are actual arguments s, a and w are formal arguments. When a function call is made, actual arguments values are copied into formal arguments.

ii) Structure as argument to the function.

struct boy { char name[20]; int age; int wt;

}; main() { struct boy={“amit”,20,45}; display();

}; void display(struct boy y) { printf(“ \n Name : %s”, y.name); printf(“ \n Age :%d”,y.age);

printf(“ \n weight %d”,y.wt); } In the above example boy is a structure, b1 is structure variable. By passing the entire structure as an argument to the function display( ),printing the values. Actual argument is b1 and formal argument is y.b1 values are dumped into y, when a function call is made.

i) passing the address of a structure as an argument to the function.

struct boy { char name[20]; int age; int wt;

}; DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 133 main() {

struct boy b1={“amit”,20,45}; display(&b1); } void display(struct bot *y) {

printf(“ \n name :%s”,y -name); printf(“ \n age :%d”,y_ ->.age); printf(“ \n weight :%d”,y ->wt); } In the above example the address of structure boy(&b1) is passing as an argument to the function

display(),printing the values. Actual argument is&b1, formal argument is *y; When we are passing the address, the receiving parameter should be pointer. We can access the members o f a structure through pointer variable to that structure by using indirect selector( ->) operator.

We can also consider that structure as return type of a function. The following example illustrates structures with functions as arguments and return type.

/*program for addition, subtraction, multiplication and division of two complex numbers using structures and functions*/ struct complex { float real; float

imag; }; struct complex a, b, c; int main() {

int ch; printf(“enter first complex no:”); scanf(“%f%f”,&a.real, &a.imag); printf(“enter second complex no:); DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving

MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 134 scanf(“%f%f”,&b.real, &b.imag); display(a); display(b); printf(“ MENU \n”);

printf(“ \n1.addition”); printf(“ \n2.subtraction”); printf(“ \n3.multiplication”); printf(“ \n4.division”); printf(“ \n Enter ur choice:”);

scanf(“%d”, &ch); switch(ch) { case 1:c=add(a,b); break; case 2:c=sub(a,b);

break; case 1:c=mul(a,b); break; case 1:c=div(a,b); break;

default: printf(“ \n your choice is invalid”); } display(c); } struct complex add(struct complex x, struct complex y)

{ struct complex t; t.real=x.real+y.real; t.imag=x.imag+y.imag; return t;

} struct complex sub(struct complex x, struct complex y) { struct complex t; t.real=x.real -y.real;

t.imag=x.imag -y.imag; return t; } struct complex mul(struct complex x, struct complex y) {

struct complex t; t.real=x.real*y.real -(x.imag * y.imag); t.imag=x.imag*y.imag+(x.imag*y.imag); DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 135

return t; } struct complex div(struct complex x, struct complex y) { struct complex t; float d;

d=(y.real*y.real)+(y.imag*y.imag); t.real=((y.real*y.real)+(y.imag*y.imag))/d; t.imag=((y.real*y.imag) -(y.imag*y.real))/d; return t; }

display(struct complex c) { printf(“ \n\t\t %f + i %f”, c.real, c.imag); } Structures within structures

Structures within structures mean nesting of structures. Nesting of structures permitted n C. We can take any data type variable a structure member, like that we can also take object of one structure as member in another structure. And we can group all the items rela ted to one particular object is also declared as structure member.

/*Example for structures within sructures*/ struct name { char *first; char *last; };

struct emp { struct name n1; int eno; float sal; };

main() { struct emp e; DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 136

printf(“enter employee details”); printf(“ \n Name : first,last”); printf(“ \n employee no and sal”); scanf(“%s%s%d%f”,e.n1.first,e.n1.last,&e.eno,&e.sal); printf(“ \n Name : %s”,strcat(e.n1.first,e.n1.last);

printf(“ \n empno :%d”,e.no); printf(“ \n salary:%f”,e.sal); } Self Referential Structures Self Referential structures are those structures that have one or more pointers which point to the same type

of structure, as their member.

In other words, structures pointing to the same type of structures are self-referential in nature.

Example:

struct node { int data1; char data2; struct node* link; };

int main() { struct node ob; return 0; }

In the above example ‘link’ is a pointer to a structure of type ‘node’. Hence, the structure ‘node’ is a self - referential structure with ‘link’ as the referencing pointer. An important point to consider is that the pointer should be initialized properly before accessing, as by default it contains garbage value.

Types of Self -Referential Structures  Self Referential Structure with Single Link  Self Referential Structure with Multiple Links Self Referential Structure with Single Link: These structures can have only one self -pointer as their member.

The following example will show us how to connect the objec ts of a self -referential structure with the single link and access the corresponding data members. The connection formed is shown in the following figure.

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 137 Example:

#include struct node { int data1; char data2; struct node* link;

}; int main() { struct node ob1; // Node1 // Initialization

ob1.link = NULL; ob1.data1 = 10; ob1.data2 = 20; struct node ob2; // Node2 // Initialization

ob2.link = NULL; ob2.data1 = 30; ob2.data2 = 40; // Linking ob1 and ob2 ob1.link = &ob2;

// Accessing data members of ob2 using ob1 printf("%d", ob1.link ->data1); printf(" \n%d", ob1.link ->data2); return 0; output:

30 40 Self Referential Structure with Multiple Links: Self referential structures with multiple links can have more than one self -pointers. Many complicated data structures can be easily constructed using DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving

MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 138 these structures. Such structures can easily connect to more than one nodes at a time. The following exam ple shows one such structure with more than one links.The connections made in the above example can be understood using the following figure.

Example:

#include struct node { int data; struct node* prev_link; struct node* next_link;

}; int main() { struct node ob1; // Node1 // Initialization

ob1.prev_link = NULL; ob1.next_link = NULL; ob1.data = 10; struct node ob2; // Node2 // Initialization

ob2.prev_link = NULL; ob2.next_link = NULL; ob2.data = 20; struct node ob3; // Node3 // Initialization

ob3.prev_link = NULL; ob3.next_link = NULL; ob3.data = 30; // Forward links ob1.next_link = &ob2;

ob2.next_link = &ob3; DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 139 // Backward links ob2.prev_link = &ob1;

ob3.prev_link = &ob2; // Accessing data of ob1, ob2 and ob3 by ob1 printf("%d \t", ob1.data); printf("%d \t", ob1.next_link ->data); printf("%d \n", ob1.next_link ->next_link ->data);

// Accessing data of ob1, ob2 and ob3 by ob2 printf("%d \t", ob2.prev_link ->data); printf("%d \t", ob2.data); printf("%d \n", ob2.next_link ->dat a); // Accessing data of ob1, ob2 and ob3 by ob3

printf("%d \t", ob3.prev_link ->prev_link ->data); printf("%d \t", ob3.prev_link ->data); printf("%d", ob3.data); return 0; }

Output:

10 20 30 10 20 30 In the above example we can see that ‘ob1’, ‘ob2’ and ‘ob3’ are three objects of the self referential structure ‘node’. And they are connected using their links in such a way that any of them can easily access each other’s data. This is the beauty of the self referential structures. The connections can be

manipulated according to the requirements of the programmer.

Applications:

Self referential structures are very useful in creation of other complex data structure s like:

 Linked Lists  Stacks  Queues  Trees  Graphs etc

Unions:

Union is a concept borrowed from structures and therefore follows the same syntax as structures. Union is a group of logically related data values of different type with the common name. And we can use . (dot) operator to access individual members of a union as in structures. 10 20 30 DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 140

Ex: union { int m; float x; char c; } code; code.m=10, code.x=12.05, code.c=’A’;

However, there is major distinction between the union and structure is in terms of storage. In structures each member has its own storage location, whereas all the members of a union use the same location. Union can handle only one member at a time.

Ex: structure, union declarations are as follows:

struct item1 union item2 { { int m; int m; float x; float x; char c; char c;

}code1; } code2; Differences between structure and union :

Structure Union Collection of values of different data types Collection of values of different data types DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving

MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 141 Declaration:

struct { Datatype1 member1; Declaration:

union { Datatype1 member1; Datatype2 member2; .

.

.

.

Datatype -n members - n; }; Datatype2 member2; .

.

.

.

Datatype -n members -n; }; The memory allocated for structure is equal to its members total size. (Memory

is allocated only when a structure variable is defined). The memory allocated for union is equal to its member size, which allocation (Memory is allocated only when a union variable is defined).

struct item1 { Int m; float x; char c;

}s; union item2 { Int m; float x; char c; }u;

Memory allocated for s is 2+4+1=7 bytes. Memory allocated for u is 4 bytes All the members can be accessed at a time. Only member can be accessed at a time.

Values assigned to one member will not cause the change in other members.

Values assigned to one member May cause the change in value of other members.

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 142 The usage of structure is efficient when all Members are actively

used in the program The usage of union is efficient when members of it are not required to be accessed at the same time.

FILES Topics covered:

Files – Concept of a file, Streams, Text files and Binary files, Basic operation on files, File input / output functions. Sequential Access and Random Access Functions A File is a collection of records that can be accessed through the set of library functions.

Record is nothing but collection of fields of related data items. These files are stored on the disk and can be accessed through file -handling functions provided by the C -standard library.

RollNo Name Total Marks Average 101 Pavan 450 70 102 Laxman 400 66 103 Dinesh 433 68 104 Simha 500 80

105 Sun 540 82 Eg: Here a file called “STUDENT.DAT” which is having 5 students’ records. And every record is collection of 4 fields.

Types of I/O: There are numerous library functions available for I/O. these can be classified into two broad categories:

a) Console I/O b) file I/O Console I/O :Functions to receive input from keyboard and write output to VDU (monitor). The screen and keyboard are called a console. Console I/O functions can be further classified into two DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 143

categories – formatted console I/O and unformatted console I/O. The basic di fference between them is that the formatted functions allow the input and output to be formatted as per requirements. The different console I/O functions are as follows:

Formatted functions : The input function scanf( ) and the output function printf( ) are called formatted console I/O functions. By using the format specifiers and escape sequence characters we can use these functions to read/print required format of information.

Unformatted functions: - The input functions like getch( ), getche( ), getchar( ) and gets( ) are called unformatted input functions and putch( ),putchar( ), and puts( ) are unformatted output functions.

Each and every function is having its own syntax and meaning.

File I/O: Sometimes it is necessary to store the data in a manner that can be later retrieved and displayed either in a part or in whole. This medium is usually a “file” on the disk. File I/O can be handled by using different functions.

Formatted functions : The file input function fscanf( ) and the file output function fprint f( ) are called formatted file I/O functions.

Unformatted functions: The input functions like getc( ), getw( ), and fread( ) are called unformatted file input functions and putc( ), putw( ), and fwrite( ) functions are unformatted file output functions.

Each and every function is having its own syntax and meaning.

File streams :- Stream is either reading or writing of data. The streams are designed to allow the user to access the files efficiently. A stream is a file or physical device like key board, printe r, monitor, etc., The FILE object uses these devices. When a C program is started, the operating system is responsible for opening three streams: standard input stream (stdin ), standard output stream ( stdout ), standard error( stderr ).Normally the stdin is connected to the keyboard , the stdout

and stderr are connected to the monitor .

Text files and Binary files: C uses two types of files, text files and binary files.

Text files: - Text file is a file consists of a sequence of characters divided into lines with each line terminated by a new line(‘ \n’). A text file is writing using text stream. We can read and write text files DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 144 using different input/output functions. Formatted input/ou tput (scanf/printf), character input/output

(getchar/putchar), and string input/output (gets/puts) functions. And these functions can work with only text files. A text file contains only textual information like alphabets, digits, and special symbols.

In actuality the ASCII codes of these characters are stored in text files.

Ex: A good example of text file is any C program file.

Binary files: A binary file is a collection of data stored in the internal format of the computer. Unlike text files, the data do not need to be reformatted as they are read and write rather, the data is stored in the file in the same format that they are stored in memory. Binary files are read and write using binary streams known as block input/output functions. Simply a binary fil e is merely a collection of bytes.

This collection might be a compiled version of a C program or music data stored in a wave file or a picture stored in a graphic file.

Differences between Text and Binary files:

The major characteristics of text files are :

1. All data in a text file are human -readable graphic characters.

2. Each line of data ends with a newline character.

3. There is a special character called end -of-file (EOF) marker at the end of the file. The major characteristics of binary files are:

1. Data is stored in the same format as that is stored in memory.

2. There are no lines or new line characters.

3. There is an end -of-file marker.

Basic operations on files: The file consists of large, amount of data, which can be read or modified depending on the requirement. The basic operations that can be performed on files are:

a) Opening a file: A file has to be opened before to read and write operations. This can be achieved through fopen() function. Syntax: FILE *fp; fp=fopen(filename,mode); DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 145

Here is a pointer pointing to the file “filename”, which can be opened in specified mode. The fopen() performs three tasks:

i) It searches the disk for opening the file .

ii) If file exists, it opens that file, if the file is not existing this function returns NULL in case of read mode. In case of write mode, it creates a new file and in case of append mode it opens that file for updating.

iii) It locates a file pointer pointing to the first character of the file.

Ex: FILE *fp; fp = fopen(“sample.txt”, ”r”); if (fp==NULL) printf(“file does not exist”); else {

.................

} b) Reading/writing a file : Once the file is opened, the associated file pointer points to the starting of the file. If the file is opened in writing mode , then we can write information by using differ ent functions like:

putc ( ): Putting a character in to the file. It works with only character data type. One character at a time can write into a file.

Ex: char ch =’a’; putc (ch, fp); putw ( ): putting or writing of an integer value to a file.

Ex: int x = 5; putw(x,fp); DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 146 fprintf(): writing a group of values into a file.

Syntax: fprintf (file pointer, ”control string”, list of arguments); Ex:

fprintf (fp, ”%s %d %d ”, name, rno, marks); If the file is opened in reading mode , then we can read information from the file, i.e. using some functions like:

getc ( ): getting a character from the file, or reading the file information character by character at a time, upto the end of the file by using this function.

Ex: char ch; ch = getc (fp); getw ( ): getting or reading integer value from a file. Ex:

int x; x = getw (fp); fscanf ( ): This function is used to read the information from a file record -wise. It is used to read more values at a time.

Ex: fscanf(fp,”%s%d%d”, name, &no, &marks); Among all the above different file i/o functions, fscanf() and fprintf() are called as formatted i/o functions. Printf and scanf are also called as formatted i/o functions.

NOTE: some compilers refer that: putc() is same as fputc() getc() is same as fgetc().

c) closing a file: After reading/writing a file ,it is needed to close that file .fclose() is used to close a file. It closes only one file at a time.

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 147 fclose (fp) :-close a file which is pointed by fp.

fcloseall ( ) :-close all opened files at a time.

Different modes to open a file: The tasks performed by fopen() function when a file is opened in each of these modes are as follows:

1. ”r” (Read) mode : opens the file that already exists for reading only. If the file doesn’t exist it returns NULL.

2. ”w”(write) mode : File is opened for writing, if the file exists its contents are overwritten and if the file doesn’t exists, then a new file is created. It returns NULL if it is unable to open the file.

f1=fopen(“sample.txt”, ”w”); 3. ”a”(append) mode : searches for the file , if it exists then appending new contents at the end of the file.If a file doesn’t exist then a file with a specified name is created and ready to get append or add.

f1 = fopen (“sample.txt”, ”a”); 4. ”r+” (Read & write mode): This is for both reading and w riting the data. If the file doesn’t exist then it returns NULL.

5. ”a+” (Append & Read) mode : The file can be read as well as data can be appended.

The two modes of binary files are:

1. “rb” (read binary) mode: Binary file is opened for reading only.

2. “wb” (write binary) mode: Binary file opened for writing only.

NOTE: While opening the file in text mode we can use either “r” or “rt”/ “w” or “wt”, but since text mode is the default mode we usually drop the “t”.

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 148 /* PROGRAM TO COPY ONE FILE INTO ANOT HER FILE */ #include int main()

{ FILE *fs,*ft; char ch; fs=fopen("sample.txt","r"); if (fs==NULL) {

puts("cannot open source file \n"); exit(1); } ft=fopen("sample1.txt","w"); if (ft==NULL)

{ puts("cannot open target file"); exit(1); } while((ch=fgetc(fs))!=EOF)

fputc(ch,ft); fclose(fs); fclose(ft); return 0; }

/* EXAMPLE PROGRAM FOR ACCESSING BINARY FILES USING fwrite( ) , fread( ) FUNCTIONS */ #include int main() {

int i,n; FILE *fp1,*fp2,*fp3; struct employ { char name[20];

int eno; int bsal; }; struct employ e[3]; fp1=fopen("EMP.DAT","wb");

for(i=0;i<3;i++) { printf(" \n Enter name, num, and basic pay \n"); DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 149

scanf("%s%d%d",e[i].name,&e[i].eno,e[i].bsal); } fwrite(&e,sizeof(e),3,fp1); fclose(fp1); fp1=fopen("EM P.DAT","rb");

fread(&e,sizeof(e),3,fp1); for(i=0;i<3;i++) { printf(" \n Name :%s",e[i].name); printf(" \n Number :%s",e[i].eno);

printf(" \n basic pay :%s",e[i].bsal); } fclose(fp1); return 0; }

Random Access to Files:

Files can be accessed either sequentially or randomly. Random accessing of files can be achieved by using some predefined C library functions: fseek( ), ftell( ), and rewind( ).

ftell( ) function: - If we wish to know where the file pointer is positioned right now, we can use the function ftell. ftell takes a file pointer as an argument, and it returns the position as long int which is an offset from the beginning of the file. It takes the following f orm:

syntax: n = ftell(fp); n would give the relative offset(in bytes).

rewind( ): - This function places the file pointer to the beginning of the file, irrespective of where it is present right now. It takes file pointer as an argument.

Syntax: rewind( fp); fseek( ) function: - The fseek( ) function lets us move the pointer from one record to another. Simply it is to move the file pointer to the desired location within a file. When the operation is successful, fseek returns a zero. If we attempt to move the file pointer beyond the file boundaries, an error occurs and fseek returns -1. It takes the following form:

syntax : fseek(file pointer, offset, position);  file pointer is a pointer to the concerned file.

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 150  Offset is a number or variable of type long, it specifies the number of positions (bytes) to be moved from the location specified. If offset is positive number, then moving forward or negative meaning move backwards.

 Position is a n integer number and it specifies from which position the file pointer to be moved. Position can take one of the following three values.

0 beginning of file 1 current position 2 end of file Eg: fseek (fp, 0L,0); - go to the beginning of the file. (Similar to rewind).

fseek (fp, 0L,1); - Stay at current position (Rarely used) fseek (fp, 0L,2); -go to the end of the file, past the last character of the file. fseek (fp, m,0); -move to the (m+1)th byte in the file fseek (fp, m,1); - move to forward by m bytes from current position fseek (fp, -m,1); - move to backward by m bytes from curre nt position fseek (fp, m,2); -

move backward by m bytes from the end.

/* PROGRAM TO ACCESS A FILE RANDOMLY */ #include int main() { FILE *fp;

long n; char c; fp = fopen("sample.txt", "w+"); // opened for both writing and reading while((c=getchar())!=EOF) // press CTRL+Z after entering the text { DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving

MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 151 putc(c,fp); } n=ftell(fp); // stores the present location of file pointer in n printf(" \n No.of characters entered = %ld \n", n);

n=0L; while(!feof(fp)) { fseek(fp,n,0); // moves file pointer to the beginning of the file.

c=getc(fp); putchar(c); n=n+5L; } putchar(' \n');

return 0; } The following program to illustrate the concept of command line arguments to file /*PROGRAM THAT WILL RECEIVE A FILENAME AND A LINE OF TEXT AS COMMAND LINE ARGUMENTS AND WRITE THE TEXT TO THE FILE */

int main(int argc, char *argv[] ) { FILE *fp; int I; char str[20]; fp = fopen(argv[1], ”w”);

printf(“ \n The no.of arguments in command line are : %d \n ”, argc); for(i=2;i

printf(“ \n Contents of the file are : \n”); fp=fopen(argv[1],”r”); for(i=2;i

{ fscanf(fp,”%s”, str); printf(“%s”, word); } fclose(fp);

return 0; } DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 153 Tables Sets Graph Trees Non-Linear DS Data Structures

Linear DS UNIT -V BASIC DATA STRUCTURES Topics covered:

Introduction to Data Structures – Linear and Non -Linear Structures – Implementation of Stacks, Queues, Linked Lists and their applications.

Introduction to Data Structures:

Data may be organized in many different ways; the logical or mathematical model of a particular organization of data is called data structure. (OR ) It is a study of different methods of organizing the data in memory and possible operations on these structures, and devices algorithms for these operations.

Data Structures = {Data items + storage methods + algorithms} The following are the activities associated with Data Structure 1. Data organization or clubbing 2. Accessing technique 3. Level of Associability

4. Manipulating selection for information 5. The Data structure should be satisfactory to represent the relationship between data elements.

Abstract Data Types Data Structures is a group of items in which each item is defined by its own identifier, each of which is known as member of the structure. An useful data type for specifying the logical properties of a data type is th e Abstract Data Type, or ADT. Fundamentally, a data type is a collection of values and a set of operations on those values. That collection and those form a

mathematical construct that may be implemented using a particular hardware or software data struct ure. Data structure is also called as ABSTRACT DATA TYPES.

Linked list Queues Stacks Array DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 154 F A B C D E Linear Data Structure : Here all the elements form a sequence or maintain a linear ordering. Non-

Linear Data Structure: These are the data structures where in the access and storage of data is not linear. Here all the elements are distributed over a plane.

Stacks:

A stack is an ordered collection of data in which data is inserted and deleted at one end (same end) called as TOP.

 Stack is a linear data structures.

 The elements in a stack can be inserted and deleted at one end called top of the stack.

 Stack operates on a LIFO (last in first out) basis.

 Stacks are associated with two operations, they are push and pop.

 Stack is also known as pushdown list.

Push: To insert an element into the stack when we try to insert elements into the stack, if there is no space in the stack, then it is said to be OVERFLOW condition (stack is full) Pop: To delete an element from the stack. When we try to delete items fr om the stack if there is no item in the stack, then it is said to be in UNDERFLOW condition (stack is empty).

Example: Representation of Stack in memory 1. Pile of plates 2. A coin stacker Insert Delete Stacks can be implemented by using

 Arrays (Static Implementation)  Linked lists (Dynamic Implementation) DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 155 Algorithm for Stack operations using Arrays: Procedure

PUSH (A, MAX, TOP, ITEM) A : Array MAX : Stack size TOP : Stack pointer ITEM : value in a cell

Step 1: check for stack overflow If TOP>= MAX -1 then Printf” stack is OVERFLOW” Return; Step 2: Increment top

TOP= TOP + 1 Step 3: Insert item at the top of the stack A [TOP] = ITEM Return Step 4: Exit

Procedure for pop (A, TOP) A : Array TOP : Stack pointer Step 1: check for stack UNDERFLOW If TOP < 0 then

Printf” Stack is UNDERFLOW” and exit Return Step 2: Return former top element of stack ITEM = A [TOP] DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving

MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 156 Step 3: Decrement pointer TOP TOP = TOP – 1 Return Step 4: Exit

Stacks using Arrays #include #include #define MAX 5 int top= -1;

int s[MAX]; void push(int x) { if(top==MAX -1) printf(" \n stack overflow"); else {

top++; s[top]=x; } } int pop( ) {

int y; if(top== -1) { printf(" \n stack underflow"); return -1; } else

{ y=s[top]; top--; return y; } }

void display() { int i; if(top== -1) printf(" \n satck underflow"); else DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving

MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 157 { printf(" \n stack elements are: "); for(i=top;i>=0;i --) printf("%4d ",s[i]);

} } int main() { int ch,a,b;

while(1) { printf(" \n stack operations"); printf(" \n \t 1.PUSH"); printf(" \n \t 2.POP");

printf(" \n \t 3.DISPLAY"); printf(" \n \t 4.EXIT"); printf(" \n enter ur choice"); scanf("%d",&ch); switch(ch)

{ case 1:printf(" \n enter an element to push "); scanf("%d",&a); push(a); break;

case 2:

b=pop(); if(b!= -1) printf(" \n deleted element is %d ",b); break; case 3:

display(); break; case 4:

exit(0); DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 158 default:printf(" \n ur choice is wrong"); }

} return 0; Application of stacks:

The following are three important applications of stack:

1. Recursion: ability to call itself.

2. Classical: deals with compilation of infix expression into object code.

3. Stack machine: certain computers perform stack operations at hardware level, and these operations enable insertions to and deletions from a stack to be made very rapidly.

The first application of the stack involves determining whether parentheses are balanced properly in algebraic expressions.

Let us concentrate on second a pplication. Consider two numbers a and b.

i.e. c = a + b Infix notation: whenever the operator is placed between the two operands then that type of expressions are called as Infix expression.

Examples:

1. a-b 2. a + b - c 3. (a + b)+(c / d) Prefix notation : where the operator precedes the two operands. It is also called as POLISH NOTATION.

Examples:

1. –ab 2. -+abc 3. ++ab/cd Postfix notation: where the operator follows the two operands. It is also called as REVERSE POLISH NOTATION.

1. ab- 2. abc-+ ab+cd/+ DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 159

In computers, usually the expression written in infix notation is evaluated by first converting into postfix expressions and then we evaluate the postfix expression. Stacks are useful for the conversion and evaluations steps.

Conversion from Infix to Postfix Expression:

Algorithm :

1. Scan the input expression from right to left taking one symbol at a time. Till end of the given infix string, Goto step 5.

2. If an operand is encountered, push into the stack Goto step1.

3. if a left parenthesis is encountered, push it into the stack Goto step1.

4. If a right parenthesis is encountered, pop the stack and append the operator to output.

Until the left parenthesis is encountered. Discard both parenthesis is encountered.

5. If an operator is encountered (current operator) co, then the top most element from the stack is retrieved (STO) and the priorities of the both the operators (CO & STO) are compared.

 If the STO (stack top operator) has higher or same priority as the current operator (CO) scanned, then STO is added to the output & CO is pushed into the stack.

 Else STO is pushed back to the stack then the current operator (CO) is also added to the stack.

Stack application - infix to postfix conversion:

#include #include #define size 20 char s[size]; int top= -1; void push(char ch)

{ top++; s[top]=ch; } char pop()

{ char ch; ch=s[top]; top--; return ch; }

char topmost() DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 160 { return s[top];

} int icp(char ch) { switch(ch) {

case'+':

case' -':

return 1; case'*':

case'/':

case'(':

return 2; return 5; case'^':

return 4; } return 0; } int isp(char ch)

{ switch(ch) { case'+':

case' -':

return 1; case'*':

case'/':

case'(':

return 2; return 0; case'^':

return 4; case'#':

return -1; } return 0; DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 161

} void convert(char a[],char b[]) { int i,j; push('#'); j=0; for(i=0;a[i]!=' \o';i++)

{ if(a[i]>='a' && a[i]<='z') { b[j]=a[i]; j++; }

else if(a[i]==')') { while(topmost()!='(') { b[j]=pop(); j++;

} pop(); } else if(icp(a[i])>isp(topmost())) {

push(a[i]); } else { while(icp(a[i])<=isp(topmost()))

{ b[j]=pop(); j++; } push(a[i]); }

} while(topmost()!='#') { b[j]=pop(); j++; } b[j]=' \0';

} int main() { char a[20],b[20]; printf(" \nEnter the infix notation:");

scanf("%s",a); convert(a,b); printf(" \nPstfix Notation \n"); printf("%s",b); return 0;

} DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 162 Evaluation of Postfix Expression: - Algorithm :

1. Scan the input expression from right to left taking one symbol at a time.

2. If an operand is encountered, push into the stack; else pop the two operand from the stack & apply the indicted operation & push the re sult into the stack.

3. Repeat the steps 1 and 2 until end of the expression.

4. Pop the Top element of the stack, which is the result of the expression.

Example: Evaluation of postfix expression 1. abc/d*+ for a+(b/c)*d infix exp.

Symbol Stack A 5 where B 5 4 a=5, b=4, c=2 C 5 4 2 / 5 2

D 5 2 2 * 5 4 + 9 Result: 9 NOTE: whenever we see a oprator in the expression we have to pop the two operands & perform that

operation of operator on it. Result is placed in stack Postfix evaluation #define size 10 int s[size]; int top= -1;

void push(int n) { top++; s[top]=n; }

int pop() { return s [top--]; }

int topmost() { return s[top]; } int eval(char a[])

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 163 { int i,x,y,dx; for(i=0;a[i]!=' \0';i++)

{ if(a[i]>='0' && a[i]<='9') { push(a[i] -'0'); }

else { y=pop(); x=pop(); switch(a[i])

{ case '+':

push(x+y); break; case ' -':

push(x -y); break; case '*':

push(x*y); break; case '^':

dx=pow(x,y); push(dx); break; case '/':

push(x/y); break; } } } return topmost();

} int main() { char a[20]; int rs;

printf(" \nEnter the postfix Notation:"); scanf("%s",&a); rs=eval(a); printf(" \nResult is: %d",rs); return 0;

} DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 164 QUEUES:

Queue is an ordered collection of data, such that the elements or data is inserted at one end and deleted at another end.

 The elements are inserted at one end called Rear and at another end called Front.

 Queue is processed on a FIFO STRUCTURE (FIRST IN FIRST OUT).

 It works on that the elements inserted first, in the element to be deleted.

 Queue is associated with the two operati ons insert and delete.

Insert: To insert an element into the queue by checking its overflow condition an element is inserted, at the rear end we can insert, then rear is incremented. If rear equal to maximum size of queue, then queue is said to be overflow condition.

Delete: To delete an element from the queue by checking its underflow condition whenever an element is deleted, front is incremented. If front is equal to zero or front is equal to rear, then queue is said to be in underflow condition.

Insertion:

0 1 2 3 4 SS f=r= -1 f r Max=5 0 1 2 3 4 Insert A f= r = 0 f r 0 1 2 3 4 Insert B f= 0, r = 1 f

r 0 1 2 3 4 Insert C f= 0, r = 2 f r A B C D A B

A A B C DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 165 0 1 2 3 4 Insert D f= 0, r = 3

f r 0 1 2 3 4 Insert E f= 0, r = 4 f r Note: Again if we want to insert it will display queue is overflow Deletion

0 1 2 3 4 Delete A f= 1, r = 4 f r 0 1 2 3 4 Delete B f= 2, r = 4 f r 0 1 2 3

f 4 r Delete C f= 3, r = 4 E 0 1 2 3 4 f r Delete D f= 4, r = 4

0 1 2 3 4 Delete E f= r = -1 f r Note: whenever we are inserting the element for the first time into the queue, then set f=0.

Algorithm for inserting an element into a queue 1. Initialize front= -1 and rear= -1 2. if rear==MAX -1 Print “Queue is overflow” and return Else Increment rear Set

rear= rear+1 D E B C D E C D E A B C D E

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 166 3. Q[rear] =ITEM 4. if (front= -1) then set front=0 5. Exit

Algorithm for deleting an element into a queue 1. Check for Queue under flow If(rear== -1) Print Queue is under flow and return Else ITEM = Q[front]// Removes an element from queue

2. Find new value of front If(front=rear)//checking for empty queue Set front= -1 and rear= -1//Reinitialize pointers Else 3. Front = front +1 Exit

Queues u sing Arrays #include #define size 5 int q[size]; int front=0;

int rear= -1; void insert(int n) { if(rear==size -1) {

printf(" \nQueue overflow"); } else { rear++; q[rear]=n;

printf(" \nelement inserted"); } } int del() {

int dx; if(rear== -1) { printf(" \nQueue underflow"); return -1;

} else if(front==rear) { dx=q[front]; front=0;

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 167 rear= -1; return dx; }

else { dx=q[front]; front++; return dx;

} } void display() { int i;

if(rear== -1) { printf(" \nQueue is empty"); } else

{ printf(" \nElements of queue are \n"); for(i=front;i<=rear;i++) { printf("%5d",q[i]);

} int main() { int n,dx,ch; while(1)

{ printf(" \nOperations on stacks"); printf(" \n1.Insert"); printf(" \n2.Delete"); printf(" \n3.Display");

printf(" \n4.Exit"); printf(" \nEnter ur choice"); scanf("%d",&ch); switch(ch) {

case 1:

printf(" \nEnter the element to insert"); scanf("%d",&n); insert(n); break; case 2:

dx=del(); if(dx!= -1) printf(" \nDeleted element is:%d",dx); break; case 3:

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 168 display(); break; case 4: exit(0); default: printf(" \nInvalid Choice");

} return 0; Linked list List: A list refers to a set of items organized sequentially.

Advantages:

 Linked list are dynamic Data Structures. i.e. they can grow or shrink during the execution of a program.

 Efficient memory utilization. Here, memory is pre -allocated. Memory is allocated whenever it is required. And it is deallocated(removed) when it is no longer needed.

 Insertion and deletion are easier. Linked lists provide flexibility in inserting a data it em provide flexibility in inserting a data item at a specified position and deletion of a data item from the given position.

 Many complex applications can be easily carried out with linked lists.

Disadvantages:

 More memory: if the number of fields is more, then more memory space is needed.

 Access to an arbitrary data item is little bit cumbersome and also time –consuming.

Advantages:

 A linked list is a dynamic data structure which means that the memory to hold the data is created at runtime (dynamic), and stored in a data structure.

 A linked list is a linear data structure. i.e. it is a collection of similar data elements called nodes. The individual elements are stored at different places in memory but still bounded together by means of pointer.

 Each node in the linked list consists of two fields, information fields and link part information fields contains data item and the link part contains the address of the most item in the list  The last node of the linked list contains a special link part called NULL pointer) i.e. any invalid address).

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 169 Disadvantages:

 It consumes more space because every node requires an additional pointer to store address of the next node.

 Searching a particular element in list is difficult and also time consuming.

Application of linked lists  Linked lists are used to implement stack, queue, trees and graphs.

 Linked lists are used to represent and manipulate polynomial P(x) = a0xn +a1xn-1+……….

 Represent very large numbers and operations of the large number such as addition, multipli cation, division.

Single Linked List #include #include #include struct node

{ int data; struct node *next; }; struct node *root=NULL;

void create() { struct node *new1,*last; int n; while(1) {

printf("enter the data or -1 to stop"); scanf("%d",&n); if(n== -1) break; new1=(struct node*)malloc(sizeof(struct node)); new1 ->data=n;

new1 ->next=NULL; if(root==NULL) { root=last=new1; }

else { last->next=new1; last=new1; }

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 170 } } void display()

{ struct node *temp; if(root==NULL) { printf("list is empty");

} else { printf(" \n elements of list are"); temp=root; while(temp!=NULL)

{ printf("%d",temp ->data); temp=temp ->next; if(temp!=NULL) printf(" --->");

} } } int length() {

int len=0; struct node *temp; temp=root; while(temp!=NULL) {

len++; temp=temp ->next; } return len; // getch();

} void insert(int pos,int n) { struct node *temp,*new1; int i; if(pos<1||pos>length()+1)

{ printf(" \n invalid position"); } else {

new1=(struct node*)malloc(sizeof(struct node)); new1 ->data=n; new1 ->next=NULL; if(pos==1) {

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 171 new1 ->next=root; root=new1; }

else { temp=root; for(i=1;inext; new1 ->next=temp ->next;

temp ->next=new1; } } } int del(int pos)

{ struct node *p,*temp; int dx,i; if(pos<1||pos>length()) {

printf(" \n invalid choice"); return -1; } else if(pos==1) {

temp=root; dx=root ->data; root=root ->next; free(temp); return dx; }

else { temp=root; for(i=1;inext; p=temp ->next; temp ->next=p ->next; dx=p ->data;

free(p); return dx; } } int main() {

int dx,pos,n,ch; create(); display(); while(1) {

// clrscr(); printf(" \n operations on linked lists"); printf(" \n1.Insert"); printf(" \n2.Delete"); printf(" \n3.Display");

printf(" \n4.Length"); DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 172 printf(" \n5.Exit"); printf(" \nEnter ur choice:");

scanf("%d",&ch); switch (ch) { case 1: printf("enter the position to insert"); scanf("%d",&pos);

printf("enter the element to be inserted:"); scanf("%d",&n); insert(pos,n); break; case 2: printf("enter t he position to delete");

scanf("%d",&pos); dx=del(pos); if(dx!= -1) printf(" \n Deleted element=%d",dx); break;

case 3: display(); break; case 4: dx=length(); printf(" \n no of nodes=%d",dx); break;

case 5: exit(0); default: printf(" \n invalid choice"); }// getch(); } return 0;

} Stacks using linked list #include #include typedef struct node

{ int data; struct node *link; }list; list *top=NULL;

void push(int x) { list *new1; new1=(list *)malloc(sizeof(list)); new1 ->data=x;

new1 ->link=top; top=new1; } int pop() {

list *temp; int y; if(top==NULL) { DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 173

printf(" \n stack underflow"); y=-1; } else {

temp=top; top=top ->link; y=temp ->data; free(temp); }

return y; } void display() { list *temp; if(top==NULL)

printf(" \n satck unde rflow"); else { temp=top; while(temp!=NULL)

{ // printf(" \n stack elements are: "); printf("%4d",temp ->data); temp=temp ->link; } } } int main()

{ int ch,a,b; while(1) { printf(" \n stack operations"); printf(" \n \t 1.PUSH");

printf(" \n \t 2.POP"); printf(" \n \t 3.DISPLAY"); printf(" \n \t 4.EXIT"); printf(" \n enter ur choice"); scanf("%d",&ch);

switch(ch) { case 1:printf(" \n enter an element to push "); scanf("%d",&a); push(a); break;

case 2:b=pop(); if(b!= -1) printf(" \n deleted element is %d ", b); break; case 3:display();

break; case 4: exit(0); default:printf(" \n ur choice is wrong"); } DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving

MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 174 } return 0; } Queues using Linked Lists

#include struct node { int data; struct node *next;

}; struct node *front=NULL; struct node *rear=NULL; void insert(int n) {

struct node *new1; new1=(struct node *)malloc(sizeof(struct node)); new1 ->data=n; new1 ->next=NULL; if(front==NULL)

{ front=rear=new1; } else {

rear->next=new1; rear=new1; } } int del()

{ int dx; struct node *temp; if(front==NULL) {

printf(" \nQueue underflow"); return -1; } else {

dx=front ->data; temp=front; front=front ->next; free(temp); return dx; }

} void display() { DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 175

struct node *temp; if(front==NULL) { printf(" \nWQueue is empty"); }

else { printf(" \nElements of Queue are\n"); temp=front; while(temp!=NULL)

{ printf("%5d",temp ->data); temp=temp ->next; } }

} int main() { int n,dx,ch; while(1) {

clrscr(); printf(" \nOperations on stacks"); printf(" \n1.Insert"); printf(" \n2.Delete"); printf(" \n3.Display");

printf(" \n4.Exit"); printf(" \nEnter ur choice"); scanf("%d",&ch); switch(ch) {

case 1: printf(" \nEnter the element to insert"); scanf("%d",&n); insert(n); break; case 2: dx=del(); if(dx!= -1)

printf(" \nDeleted element is:%d",dx); break; case 3:

case 4:

display(); break; exit(0); default:

DEPARTMENT OF HUMANITIES & SCIENCES Programming for Problem Solving MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY 176 printf(" \nInvalid Choice"); } return 0;

} } Case Studies Case 1: Student Record Management System The main features of this project include basic file handling operations; you will learn how to add, list,

modify and delete data to/from file. The source code is relatively short, so thoroughly go through the mini project, and try to analyze how things such as functions, pointers, files, and arrays are implemented.

Currently, listed below are the only features that make up this project, but you can add new features as you like to make this project a better one!  Add record  List record  Modify record

 Delete record Case 2: Library Management System This project has 2 modules.

1. Section for a librarian 2. Section for a student A librarian can add, search, edit and delete books. This section is password protected. That means you need administrative credentials to log in as a librarian.

A student can search for the book and check the status of the book if it is available.Here is li st of features that you can add to the project.

1. You can create a structure for a student that uniquely identify each student. When a student borrows a book from the library, you link his ID to Book ID so that librarian can find how burrowed particular book.

2.You can create a feature to bulk import the books from CSV file.

3.You can add REGEX to search so that a book can be searched using ID, title, author or any of the field.

4.You can add the student login section.