c Study Material

8/12/2019 c Study Material

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Course Modules

Course Modules

Chapter 1: Introduction to Program Design

Chapter 1: Introduction to Program Design

Chapter 2: Programming Environment

Chapter 2: Programming Environment

Chapter 3: History of Programming Language

Chapter 3: History of Programming Language

Chapter 4: Structure of C Program


Chapter 5: Data Types


Chapter 6: Identifiers


Chapter 7: Basic I/O



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Chapter 9: Arrays

Chapter 9: Arrays

Chapter 8: Control Structures

Chapter 8: Control Structures

Chapter 10: Functions


Chapter 11: Advanced Control Constructs

Chapter 11: Advanced Control Constructs

Chapter 12: Storage Class and Scope Rules

Chapter 12: Storage Class and Scope Rules

Chapter 13: Advanced Functions

Chapter 13: Advanced Functions

Chapter 14: Recursion

Chapter 14: Recursion


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Chapter 1: Introduction to Program DesignChapter 1: Introduction to Program Design

What is a Program ?What is a Program ?

Stages of program developmentStages of program development

Some definitionsSome definitions


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Lets understand what a Program is

A Program is a set of instructions to solve a problem.

And now define an Algorithm

An Algorithm is a step by step solution to a problem

But both sound similar? So what is the difference ifany?

Program and an algorithm represent solutions to problems , but a

program is written in a programming language and an algorithm is not

language specific. It is written in English like language called . So we

can say that a program is an implementation of an algorithm in aspecific programming language.



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Program design is very important before coding the program.

Programmer must consider all aspects of the program in detail before

coding a program.

Why a program at all?

A program is not the problem: it is a solution to a problem. Henceproblem definition is very important.

Problem definition

Programmers are very clear about the input to the program and the

output from the program and constraints under which the program has

to operate.



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Outlining the program structure

The next step after the problem definition is to decide how to solve the

problem. We use the top-down approach. It means that decompose

the whole problem into the number of independent tasks, and then

cut the tasks unto smaller subtasks and so on until they are small

enough to be grasped by mind. The task and subtasks are nothing but

functions. Each small module or tasks can be easily programmed and

linked together in the main program.

Algorithm development

An algorithm is any well defined computational procedure that takes

some value or set of values, as input and produces some value, or set of

values, as output.


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Algorithm are never concerned with software engineering issues of

data abstraction, modularity, error handling etc. It is pure logic.

Enough time must be always spent in algorithm development.

Selection of control structure

Control structure are nothing but the way to direct the flow of

execution. the three basic control structure are:

1. Sequence structure :- control flow goes from one statement toanother in sequence.

2. Selection structure :- Based on the condition, flow of control may go

to different in the program as in the if....else statement.


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3. Looping structure :- It is used when a set of instruction is to be

evaluated repeatedly.

Program Coding

As explained above, program is always to be coded into small

procedures i.e. to achieve modular design.

Meaningful variable name are to be used.

For example, area = length * breadth is more meaningful thana = l*b;

Function name must be meaningful so that anybody could understand

it's functionality in the program.


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Code must be well documented. Comments must be used whenever

necessary.

To increase the readability of the code, proper indentation must be

used. For example the following code :

if (x


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Use indentation to write it as

if ( x < y )

{

flag = TRUE;

printf(" x is larger than y");

}

else

flag = FALSE;


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Program Testing

Detection of error is called program testing. It is very difficult to

write an error free program in the first time even by expert

programmer.

Error type

Syntax Error :- Violation of rule of the language result in the

syntax error. Compiler detect it at the time of compilation.

Logical Error :- This cause incorrect result. This is due to the lackof emphasis on the algorithm development.

Run-time Error :- Errors such as mismatch of data type or

referencing an out of range array element or division by zero result

in the run-time error. Program may give wrong result.


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Let us take an example. Mr.Samasya staying in Delhi wants to

purchase a book from Calcutta. He approaches Ms. Samadan to solvethe problem. Hence buying a book is the problem. Now, Ms. Samadan

starts dividing the problem into small tasks. She jots down the various

steps - enquire whether the book is available, book a ticket, purchase

book, return ticket. These are stepwise solution to the problem. (Analgorithm). She then sends one of her staff members to

Calcutta and Mr. Samasya is very happy. So,

PROBLEM DESIGN ----->ALGORITHM------>PROGRAM

Seven steps in all - This is what program design is all

about!!!


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Chapter 2: Programming EnvironmentChapter 2: Programming Environment

Various programming environmentsVarious programming environments

Various stages while executing a C programVarious stages while executing a C program


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Various programming environments

Entering a Program

Once the program has been written, it must be entered into the

computer. Most new version of C include a screen editor. To enter anew program, it must be typed into the editing area. Once the

program has been entered it should be saved before it is executed.

Select Save As from the File menu and supply a program name such asarea.c. Once saved, the same program can be recalled by selecting Open

from the File menu.


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Compiling & Executing To compile and execute, select Run from

the Debug menu. If the program does not compile successfully, alist of error will appear in the separate window, otherwise,

program will ask you for input (if any) and display output within

the new window.

Entering a Program

The program must be entered into a file say area.c. If thefile is created with the help of a text editor, either ed or vi. The

command for calling the editor and creating the file is:

ed filename

If the file already existed, it is loaded else a new file is created.

Various stages while executing a C program



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Compiling and linking

The compiling command is

cc filename.c.

If there is no error object file filename.o will be created. Linking with

a library file such as sqrt() are done automatically.

Executing

Use the command a.out and get the desired result.

Note: Linker always gives executable object code the same namea.out. In order to save a program from overwriting while compiling

another program you should rename the file by command

mv a.out filename.



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Generation of computer languagesGeneration of computer languages

Chapter 3:History of Programming LanguageChapter 3:History of Programming Language

Structured, Functional, Modular ProgrammingStructured, Functional, Modular Programming

Introduction to C languageIntroduction to C language


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The olden days of machine language

The computer was an electronic machine in the 1950s. The capabilities

of this electronic machine as a computing machine have increasedphenomenally in the subsequent years.Since the earlier days

programmers have been looking for various ways of feeding computers

with the most appropriate instructions to carry out the task in the best

possible manner. Thus the earliest computers had to be programmedby directly loading their memories with machine level instructions.

Generation of computer languages



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The advantage was:

It was very fast as the program directly interacted with the

machines hardware.Disadvantage

It was very cumbersome to translate the program to machine level

instruction.

Different machines from different vendors had different sets ofmachine instructions.

Whew! Different different and different --- You can imagine how

difficult that was.


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Assembly Languages

This was the first refinement to the cumbersome machine languages.Using assembly languages a programmer can represent a computation

using textual mnemonics to represent instructions and data. Special

software called assemblers can translate such representation i.e.

Assembly language program into a set of machine level instructions.Advantage:

Since it uses text mnemonics to represent the program it is

comparatively easier thanmachine language.


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Disadvantage

Assembly languages are machine-dependent i.e. the program writtenfor a certain model of the machine may not be portable on a different

machine.

OOPS! That means I have to write different code fordifferent machines! Thats bad news!


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The High Level languages

The high level languages like C, Fortran ,Cobol etc. solved this

problem of machine dependence.These languages had standardized

ways of writing code and also had a language syntax so thatprogramsbecame more readable. The high level languages were mostly

general purpose with few exceptions like COBOL and others.The

translation from high level code to low level code(i.e.. The machine

level instructions) was done the compiler or the interpreter.(RememberAssemblers!)


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Understand terms- Structured,functional,modular

Structured Programming

In 1968, Computer Scientist Edsger Dijkstra of the Netherlands

published a letter to the editor in the Communication of the ACM

(Association of Computing Machinery) containing a title "GOTOStatement considered harmful". GOTO is a command available in all

the languages (including BASIC) to transfer control to a particular

statement. For the last 25 years, Dijkstra has been crusading for a

better way of programming - a systematic way to organize programs -called Structured Programming.

Structured Programming has been called arevolution in programming

and one of the most important advances in computer software of the

past two decades.


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There is no standard definition of structured programming available

but is often thought to beprogramming without the use of a GOTO

statement. Indeed, structured programming does discourage thefrequent use of GOTO but there is more to it than that.

Features of Structured Programming

Top-down analysis for program solvingModularisation for program structure and organization

Structured codes for the individual modules.

A High Level Language supports several control statements (also called

structured control statements or structured code) to produce a well-organised (structured) module.


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These control statements represent conditional and repetitive type of

executions. Each language has different syntax for these statements.

In PASCAL, the IF and CASE statements are examples of conditional

execution whereas FOR, WHILE and REPEAT statements represent

repetitive execution. In BASIC, FOR-NEXT and WHILE-WEND are

examples of repetitive execution.

Problems with Structured Programming

Analyzing the reasons for the failures in program development revealsthat there are weaknesses in the procedural paradigm itself. No matter

how well the structured programming approach is implemented, large


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Chapter 3:History of Programming LanguageChapter 3:History of Programming Languageprograms become excessively complex. What are the reasons for this

failure of procedural languages? One of the most crucial is the role

played by data.

Data Undervalued

In a procedural language, the emphasis is on doing things. And the

subdivision of a program into functions continues this emphasis.

Where does data fit in this paradigm? Data is usually the reason for a

program's existence.

Thus Structured ness is only one aspect of modular design. When the

project becomes very large management of the modules themselves

becomes a serious burden. The quest for finding a solution has led tothe popularity of object oriented programming in the recent years.

Structured is good Object oriented is more real-world I

suppose!


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Introduction to C language

C is a general purpose, structured programming language. It was

developed at AT&T's Bell laboratories of USA in 1972 by a single

person Dennis Ritchie.

In 1970s, the work on Unix system was going on. it was being writtenin Assembly level language (ALP), a language which uses simple

English words like MOV, ADD etc. But that was very difficult to

debug. So a new language C was developed along with Unix. Although

few high level language existed but they could not get popularity due toone reason or other.

The table below shows the evolution of C :


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YEAR LANGUAGE DEVELOPED BY REMARKS

- ALP - Difficult to debug

1960 ALGOLInternational

committeeToo general

1963 CPLCambridge

UniversityBig size

1967 BCPL Martin Richard No data types

1970B

Ken Thomson Very specific

1972 C Dennis Ritchie Versatile


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The growing popularity of C, changes made into over years has created

a necessity of its standard definition. It was done in 1983 by AmericanNational Standard Institute (ANSI)

That's quite an effort. We have A's then B then C


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Chapter 4: Structure of C ProgramChapter 4: Structure of C Program

Basic structure of a C programBasic structure of a C program

Using Comments in CUsing Comments in C


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The basic structure of the C program is as follows:

Ex: To print a message on the screen

#include

//Header FileInclusion

void main()//Start of the main function

{

printf("This is my first program in C");

//Executable statements

}

//End of main()


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Chapter 4: Structure of C ProgramThe above program prints the message This is my first program in C

on the screen.

The first section shows header file inclusions. These header files contain

the definitions for the various funtions and keywords used in the

program. Here, the header file is stdio.h and this basically contains the

input output related functions.(For the time being).

The main() is the start of the program. A function is denoted by ().

void indicates that the function does not return any values. main() is

the name of the function .

The executable lines are terminated with a ; and here it displays the

message on the screen. printf is a function used to display data on thescreen

Shall we dissect this program and understand the contentsplease?


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Comments in C

Comments are almost always a good thing. Comments are used to

inform the person looking at the listing what is being done.

This type of comment begins with the /* character pair and ends

with */, not the end of the line.

While this style is not generally used in C++, it has uses in special

situations.

You can write a multi-line comment with only two comment symbols:

/* this is a potentially very long

multi-line comment */



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The main() starts with a { and ends with a }. This

is called a block.

I got it! But what is that // doing here?

You can also insert a /* */ comment anywhere in the middle of a

program line:



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The building block of C programs are functions. A function is a

subroutine that may include one or more statements designed to

perform a specific task. Writing a C program means writing

functions and putting them together.

Let's take a bigger example.



/* This program displays the cosine of an angle*/

#include #define PI =3.1416

main()

{ int angle=60;

float x,y;x=(PI/180)*angle;

y=cos(x);

printf("cos 50 degree is %f", y);

}


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SECTIONS MEANING EXAMPLE

Documentation set of comments like

name, use of programand others details

/* This program

displays the cosine ofan angle */

Link instruction to compilersto link function from

system library.

#include

Definition symbolic name

definition.

#define PI =3.1416


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SECTIONS MEANING EXAMPLE

Global Declaration variables whichcan be used in

different function.

/* No such declarationin this program */

Main()Program

tells compilerabout variable

used in the

executable part.

instruction to

execute

main() { int angle=60;float x,y;

x=(PI/180)*angle;

y=cos(x);printf("cos 50

degree is %f", y)}

Declaration

Execution



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Display can well be done in main() function only but for proper

work division display() function was used. In computer

program, it becomes a complete necessity.It will be explained further in coming chapters.



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Datatypes in CDatatypes in C

Constants and variablesConstants and variables

Escape sequencesEscape sequences


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Datatypes in C

The fundamental building blocks of any language are the datatypes it can

handle since a program has to represent data in order to do useful processing .

These datatypes are used in all languages to declare variables or constants

which will contain values when the program is running.C supports manydifferent types of data, each of which may be represented differently within

the computer's memory. the basic data types are listed below.

Chapter 5: Data TypesChapter 5: Data Types


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char single character 1 byte -128 to 127

int integer quantity 2 bytes or one word

(varies from one

compiler to another)

-32,768 to

32,767

float floating-point number 1 word(4 bytes)3.4e-38 to

3.4e+38

DATATYPE DESCRIPTION MEMORY

REQUIREMENTS

RANGE



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In addition there are a no. ofdata type qualifiers short, long, signed

and unsigned which can be used to augment the basic data types. The

size and range of the basic data types using these qualifiers is listed in

the table below.

TYPE SIZE RANGE

char or

signed

char

1 byte -128 to 127

unsigned

char1 byte 0 to 255

int or

signed int2 byte -32,768 to 32,767


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TYPE SIZE RANGE

unsigned int 2 byte 0 to 65,535

short int or

signed int

1 byte -128 to 127

unsigned

short int1 byte 0 to 255

long int or

signedlong int

4 byte -2,147,483,648 to 2,147,483,647

unsigned

long int

4 byte 0 to 4,294,967,295



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float 4 byte 3.4e-38 to 3.4e+38

double 8 byte 1.7e-308 to 1.7e+308

long

double 10 byte 3.4e-4392 to 1.1e+4392

TYPE SIZE RANGE

The standard headers and contains symbolic

constants for all of these sizes and other information.

Whew! That quite difficult. So many types and such large

numbers! Is there an easy way out!!?



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To calculate the range for any datatype is very easy. For unsigned

numbers the range is0 - 2n-1

For signed numbers the range is

- 2n-1 to 2 n-1 -1

That's perfect and so very easy to work out!!!

Although so many datatypes have been mentioned the fundamentaltypes are char, int,float and double.



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VARIABLES

Variables and constants are the basic data objects manipulated in aprogram. before using a variable it must be declared. Expression

combines variables and constants to produce new values

Rules for naming variables:

1.consists of a-z, A-Z, 0-9 but first character must be a letter.

2.case-sensitive.

3.underscore character can also be included.

4.special characters like *,-,+,',"" are not allowed.

5.blank space is not allowed within a variable name.

note: name of the variable should denote its use.



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ex. sum, average_class, fun2.

note: Ram ,ram, RAM are different variable names.



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CONSTANTS

A constant is a quantity that does not change.

A integer constant like 1234 consists of sequence of digits. It can be

decimal, octal or hexadecimal.

ex. 2415(decimal), 0xabc2(hexa), 0243(octal).

note:10,000(comma), 10-20(hypen or blank), 0900(preceded by 0) are

invalid integer constants.

A real constant is a base 10 number that contains either a decimal point

or an exponent or both.

ex. 1., 2.543, 0.9453e-34.



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A real constant is a base 10 number that contains either a decimal point

or an exponent or both.

ex. 1., 2.543, 0.9453e-34.

note: 1. 1,00.00(comma), 2e+3.24(real exponent), 3e 10(blank space) are

invalid real constants.

2. Integer constants are exact quantities but real constants may be

approximations. 1.0 might be represented within the computer as0.99999 or 1.00001.


A character constant is a single character enclosed in a apostrophe.

ex. 'a', '5', '*'.

note: ASCII characters showing the decimal equivalent of seven bits

represent a character in computer.


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Certain nonprinting characters, as well as the backslash(/) and the

apostrophe('), can be expressed in terms of escape sequences. Suchescape sequences always represent single characters, even though they

are written in terms of two or more characters.



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backslash \\ 092

null \0 000

A string constant consists of any number of consecutive

characters (including none), enclosed in quotationmarks("").

ex. "hello", "243-45+32", " ".

note: 1. 'A' and "A" are not equivalent.

2. The compiler places a null character(\0) theend of every string constant.

CHARACTER ESCAPE SEQUENCE ASCII VALUE



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Shall we summarize the whole thing?Constants are those whose values do not change.For ex. India is a name constant, 10 is an integer constant and15th August 1949 (Indias independence) is a date constant.

The co-ordinates for the line are integer variables, a personsname is a character variable and so on.

In technical terms when we declare a variable then we speicfythe datatype and the variable name. Thus a variable name is thename given to a memory location.

Gotcha! When we want to store data, we require acontainer,a space to store it and the value stored maychange and thats why it is exactly called a variable.


Ch 6 Id ifi


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Chapter 6: IdentifiersChapter 6: Identifiers

Objective:

Declaring a variable


Operators and expressionsOperators and expressions

Precedence of operatorsPrecedence of operators

Ch t 6 Id tifi


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All variables must be declared before its use. A declaration specifies a

type and contains a list of one or more variables of that type.

ex. int number, average, line[100];

Variable can also be initialized in its declaration.

ex. int number=0;

A qualifierconst can be applied to the declaration of any variable to

specify that its value cannot be changed.ex. const float mean=2.456383;



Ch t 6 Id tifi


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OPERATORS AND EXPRESSIONS

Various elements of the program like constants, variables, array

elements, function references can be added together by various

operators to form expression

ARITHMETIC OPERATORS

They are binary operators as they work with two operands.The operators are + , - , * , / and % (modulo operator).




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There is a unary (minus operator) which multiplies its operand by

1 ie. It switches the sign.

Example:

int no1=10;int no2=20;

printf( no1+no2); //Will print 30

printf(no2%no1); //Will print 0

printf(no2%3); //Will print 2




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The Increment and Decrement operators

They are the ++ and -- operators

The ++ operator increments the operand by 1 and the operatordecrements its operand by 1.


int no1=10;

no1++;printf(no1); //Will print 11 as the above

statement

is equivalent to saying no1=no1+1;


f


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There are a prefix and postfix increment/decrement operators . Both

the forms are equivalent if used separately without the assignment.

But when the latter is done the meaning of the operation changes.


For ex.

int no1=10;

no1++; (or) ++no1; will mean the same.

But,

int result = no1++; ----------------

Statement1

int result = ++no1; ----------------

Statement2


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Statement1 will cause assignment to take place first followed by

increment(postfix increment)while

Statement2 will cause increment to take place first followed byassignment(prefix increment).

Thus result will have 10 if statement1 is executed and result will have 11

if statement2 is executed.

Assignment followed by operation in postfix and reverse inprefix. Good!


Ch t 6 Id tifi


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Type Conversions

When an operator has operands of different types they undergo type

conversion before the expression takes its final value. If either operand

is long double, other is converted to long double.

Otherwise , If either operand is double, other is converted to double.

Otherwise , If either operand is float, other is converted to float.

Otherwise , convert char and short to int.

This conversion takes place automatically.



Ch t 6 Id tifi


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RELATIONAL AND LOGICAL OPERATORS

The term relational specifies the relationships that the values canhave with each other. Expressions that contain relational operators

return true or false.

The relational operators used in C++ are

Operator Action

> Greater than

>= Greater than or equal< Less than


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The Logical operators

They are so called because they return a logical value ie. True or false.They are used with relational operators in expressions.The operators

used are

Operator Action

&& Logical AND

| | Logical OR

! Logical NOT




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The Bitwise Operators

C++ supports a full complement of bitwise operators . Bitwise

operation refers to testing,setting or shifting the actual bytes in a wordwhich correspond to the char and int data types and variants.

Operators Action

& Bitwise AND

| Bitwise OR

^ Bitwise exclusive OR

~ Bitwise NOT>> Shift operator


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The ternary operator

C++ contains the very powerful and convenient operator that replaces

certain statements of the if-then-else form. It takes the general formExp1?exp2:exp3;

Exp1, the first expression1 is evaluate. If it is true then Exp2 i.e. The

expression2 becomes the value of the expression . If exp1 is false then

exp3 ie. Expression3 is the value of the expression.There are many more operators and will be discussed with the

relevant topics.





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Precedence of operators

HIGHEST

! ,~ , ++, -- , (type) , *,&, sizeof

* , / , %

+ , -

=

= = , !=

&

^

|

&&




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| |

?:LOWEST= ,+= ,-= ,*= ,/= etc.

pChapter 6: Identifiers

So ( ) (parenthesis or brackets)have highest priority andshorthand assignments the least.Must keep this in mind whilewriting expressions.




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UNARY OPERATOR

These operator works on single operator to give a new result. Most

common example is unary minus such as -45.

Increment and decrement operator

The increment operator adds one to the operand while decrement

operator subtract one from the operand. Now comes the question what

is the difference between the prefix and postfix increment operator i.e.n++ and ++n. Both increment the operand by 1 but ++n increment n

before it's value is being used.

ex: if number=10, then a = number++; sets a to 10 although number is

incremented to 11.while a = ++number ; sets a to 11.

sizeof operator determines the number of bytes allocated to various

type of data item.





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ex: sizeof (integer) return 2 while for the declaration char madam[]

="meenakshi"; sizeof madam will return 10(one extra for null

character)

Casting is used to convert value of a expression to a different data type if

desired. Desired format is

(data type) expression

ex: if x is declared as integer with value 2, and y is declared as float

with value 3.5, then (x+y) % 2 is invalid because first operand need to be

integer. So to force operand to integer value casting is done as

((int) (x+y)) % 2





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note: data type associated with the expression is not changed by a cast.

Rather it is the value of the expression which undergoes change. Here

(int) (x+y) will have value 5.

ASSIGNMENT OPERATOR AND EXPRESSIONS

Expression such asi = i + 4

can be written in short hand form using arithmetic assignment operator

+= as

i += 2.Similarly other arithmetic operator can be used as assignmentoperator.

note: there should not be any blank space between + and = in arithmetic

assignment operator.





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CONDITIONAL OPERATOR

The statements

if(a>b)

max=a;

else

max=b;

finds the maximum of two number a and b. The sort hand rule is to use

conditional operator ( ? : ). Thus simple way to write above statement is

max = (a>b) ? a : b;


PRECEDENCE

Precedence means order of evaluation. Operator with higher

precedence level is evaluated first.




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While associativity is the order in which consecutive operations within

the same precedence group are carried out.





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OPERATOR

CATEGORY

OPERATORS ASSOCIATIVITY

Unary - ++ -- ! sizeof(type)

R L

Arithmetic * / %(same

precedence) + -

L

R

Relational

operators

> >= <


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OPERATOR

CATEGORY

OPERATORS ASSOCIATIVITY

Conditional

operator

? : L

R

Assignment

operator

= += -= *= /= %= L

R

p




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Example :-

Evaluation of expression:

n=a*b/2+3/2*b+2+d; where a=3, b=2,c=3.4; n is declared as int.stepwise operation:

n=3*2/2+3/2*2+2+3.4

n=6/2+1*2+2+3.4 //note:3/2 is 1 not 1.5 as it is an integer division

and hence result is also integer.n=3+2+2+3.4

n=10 //note: n is declared as integer and hence can take

only integer value. It is assigned

10 ,not 10.4.

p

We have been talking of expressions so far can wehave a little more detail please?




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EXPRESSIONS

Operators , constants and variables are the components of expressions.

An expression is a valid combination of the above mentionedelements. Great!

Order of evaluation

Neither C nor C ++ specifies the order in which the subexpressions

of an expression are evaluated. This leaves the compiler free to

rearrange an expression to produce more optimal code. For ex.X=exp1+exp2;

This statement does not ensure that exp2 will be evaluated after

exp1.




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Type conversion in expressions

When constants and variables of different types are mixed in

expressions they are converted to the same type. This is called

type promotion. The compiler converts all operands upto thetype of the largest operand . The diagram can be shown as

follows:

Okay! Since lower dataypes are converted to higherdatatypes it is called promotion.




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CASTING IN EXPRESSIONS

We can force an expression to be of a specific typr by using a cast. Thegeneral form of the cast is

(type) expression

Technically casts are operators. A cast is unary and has the same

precedence as any other unary operator.

Short-hand assignment

There is a variation of the assignment statement that simplifies coding

of some types of assignment operations.

The are the +=, -= , *= , /= .

This notation is widely used in programming.




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Various input output functionsVarious input output functions




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C offers library functions for number of input/output operation like

getchar, putchar, scanf, printf, gets, puts. Most program begins with the

preprocessor statement #include . This header file gives

required information to the library functionscanf and printf.

getchar() and putchar() Function

getchar() takes a single character from the standard input device

generally keyboard.

char c= getchar(); statement assigns a single character inputted from

keyboard to the variable c.

Similarly putchar(c) function puts a single character c on the standardoutput device monitor.




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Inputting data through scanf function

scanf() function is used to enter any datatype, an integer, a float or a

string.

eg: scanf("%d %f %s , &n,&interest, message);

The control string %d %f %s indicate that arguments n, interest,

message represent integer, float, string respectively as per its

declaration.

note: never forget to put &(ampersand) before variable name which arenot string or an array name.

note: A variable declared as character type will scan its ASCII value if

the control string is %d meant for integer.




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Outputting data through printf function

printf() perform the similar function as scanf but to output the data.

eg: printf("%d", n);

note: No & is used while outputting the data.




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Conversion string Corresponding controlled variable

type

%c character

%d integer

%e float with exponent( in output mode),

float (in input mode)

%f float without exponent( in output

mode), float (in input mode)

%g float using e-type and f-type. Trailing

zero and decimal point will not will be

displayed( in output mode), float (in

input mode)

%o Octal integer


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scanf(Revisited)

In case of string, %s will be able to control the input of a string only up tothe point a blank space is met. To solve this problem, we use control

string as %[ ABCDEFGHIJKLMNOPQRSTUVWXYZ12345;'./] .

Now inputted string may take all character specified inside [] and willterminate inputting string when any character outside this set is given as

input.

Another way to input string is by using the control argument

[^(character)]. Now the program will input the string until a character

or a escape sequence is inputted.




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printf (Revisited)

It is possible to out the formatted data for example :to specify the

maximum number of decimal place for a float data type or maximumnumber of characters for a string.

Minimum width and precision may be specified for a float type data.

Minimum width is to limit the number of digit or character to a

specified limit while precision set the number of digit after the decimalpoint.




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Example of formatting a float:

a=906.324

printf ("%7f %7.3f %7.1f ",a,a,a) output on execution will be 906.324000

906.324 906.3

printf ("%f %.3f %.1f",a,a,a) output on execution will be 906.324000

906.324 906.3

printf ("%e %.5e %.2e",a,a,a) output on execution will be 9.063240e+02

9.06324e+02 9.06e+02




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In first example, field width is 7 and a has also 7 character width, so whole

number will be outputted. Precision is specified after field width with a

point. Default precision is 6 character after decimal. If field width

specification is more, then leading blank will come in the output before the

number.

Example of formatting a String:

char message[10];

printf ("%10s %20s %10.5s %.5",message,message,message,message)




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if message is assigned electronics during program, output on execution

will be electronics electronics elect elect

Even though electronics contains 11 character and field width

specification is only 10,the first string breaks the minimum field width

criteria. Second string is right justified within the specified width.

Precision criteria of 5 will just allow 5 character to be outputted and

field width criteria will work as earlier.


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Chapter 8 : Control Structures


C t l fl i th i hi h t l fl i


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Control flows is the manner in which control flows in a program.

It's type are :

1.sequential : control flows from one statement to other in sequence.

2.conditional : control flows as per the condition which can be either

true or false.

3.Iterative : control flows in a loop repeatedly

Any high level programming language has three features viz.Sequence,Iteration and Decision.Since C is a structured and High level

language it also has these constructs .

Selection statements imply decision.The constructs available here are

the if construct and the switch construct.

Selection statements(if and switch)




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The if constructThe general format is

if(expression)

statement;

else

statement;

if(expression)

statement;else if(expression)

statement;

else

statement;

The other form of if is as follows:




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Example. Accept a number from the user and display if it is an even or

odd number.

The if is an alternative to the ternary operator I guess!

#include

void main()

{

int no; //Declare a variable to

accept the number

printf(Enter the number);

scanf("%d); //Accept input from the

user

if(no%2==0 //Check for odd or even

no.the expression

evaluates




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printf(Even number); //to a true or false.

else

printf(Odd number); //Executable statement

}Let us consider some more examples:

1. if (speed > 60)

printf("drive slowly");

else

printf(" your speed is all right"); //note the indentation i.e. the

way code are written with proper spacing.

2. if (square) {

scanf ("%f",&side);

area = side*side;




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printf("area of square is: %f",area);

}

else {

scanf("%f %f",&length,&breadth);area = length*breadth;

printf("area of rectangle is: %f",area);

}

note: square must be assigned a non zero value before the second

example is being executed.

note: If there are more than one statement are to be executed if thecondition is true or false, they must be put under braces.

An example with if elseif

Accept an alphabet from the user and check if it is a vowel




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#include

void main()

{

char alphabet; //Declare a variable

to accept the alphabet

printf(Enter the alphabet);

scanf("%c",&alphabet); //Accept

input from the user

if((alphabet==a) || (alphabet==A)) //The expression

evaluates

printf(vowel); //to a true or false

else if((alphabet==e) || (alphabet==E))

printf(vowel); //Executable




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statement

else if((alphabet==i) || (alphabet==I))

printf(vowel);

else if((alphabet==o) || (alphabet==O)) //The

expression

uses logicaloperators

also

printf(vowel);

else if((alphabet==u) || (alphabet==U))

printf(vowel);




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The switch construct

Switch statement is called a multiple-branch selection statement. It

successively tests the value of the expression against a list of integer or

character constants . When a match is found the statements associated with

that constant are executed.

else

printf(consonant);

}




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break;

}

The general form of the switch clause is as follows:

switch(expression)

{

case constant1: statement;

break;

case constant2:statement;




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Loops or iteration is another characteristic feature of any high levellanguage. This feature allows statements to be executed repeatedly

until a certain condition is reached. To understand the loop lets take a

real life example of a loop. Consider a relay race consisting of four

members. Here the athletes run around the track and pass on the rodtill the fourth player finishes. The components that we see are as

follows - there is astart condition i.e.. The first player starts the race,

there is astop condition the fourth player stops the race, there is an

action repeatedi.e.. Running and of course there is acounter , the judgewho counts the four athletes starting from one to four.

8.2 Looping statements(for,while,do..while)8.2 Looping statements(for,while,do..while)




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Components of a loop

Similarly , in an iteration loop the above mentioned components should

ideally be present.If some of the components are missing it may result in

an infinite loop i.e. A loop which runs for infinite times.

C provides a number of looping constructs which may be used in

iteration problems.The following are the loops:

The for loop

The general form of the for loop is as follows:for (initialization;condition;reinitialization)

statement;




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The initialization section is used to set the loop counter variable in

other words sets the start condition. Condition specifies the stop

condition and is a relational expression and this determines when the

loop will exit.

The reinitialization section increments or decrements the counter

variable according to the context of the loop. Statement indicates the

action repeated.

Ex.Print the first ten odd numbers.

Let us identify the four components in this simple loop problem.The start condition is 1 and stop condition is 10, action repeated is

printing of numbers .



h f l ill b i f ll


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The for loop will be written as follows:

for(int ctr=0,no=1;ctr


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In this example the counter has been decremented.

Okay!Reinitialization can both be increment and decrement. The

above loop rus for 100 times

Let us see some more examples.

Ex: Accept 10 alphabets from the user and convert them to uppercase if

they are in lowercase and vice versa.

#include //Header file inclusion

void main() //Main function

{

char alphabet; //Declaration of variables



for(int ctr=0;ctr


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for(int ctr=0;ctr=65 && alphabet


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scanf( %c ,&alphabet); //Accept the input

if((alphabet >=65 && alphabet =97 && alphabet


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In this example we have used some relational operators and relational

operators also.

ASCII link

Suppose I write for ( int I=0 ; ;I++) ,is it valid?

Very much. This is called an infinite loop where the condition part always

returns a true value.

This is a bodyless loop , a loop which has no action to be performed except

for iteration. We will see one such example when we do arrays .

One more question, for(int I=0;I


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The while loop

The syntax for the while loop is as follows:

Example:

Accept characters and display till the user presses n;

while(Condition)

{

}




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#include

void main(){

char ch= ; //Declaration of variables

while(ch!=n) //Accept characters till user enters n

{sanf("%c",&ch);

printf(ch); //Display characters

}

}




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Thus a while loop is normally used when the number of iterations are

not exactly known as in the above case.

Consider another example.

Print the first ten odd numbers.

#includevoid main()

{

int counter;

int number=1;




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while(counter < 10)

{

printf(number);

number+=2;

}

}

There is something wrong,the initialization and reinitializationpart of loop is missing I suppose.




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Excellent! This may result in undesired consequences like infinite

loops. This is a logical error on the part of the programmer.

The correct code would be as follows:

int counter=0; //Statement 1

while(counter


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3.The do..while loop

The general structure of the do.while loop is as follows:

Then what is the difference? Why two loops doing the samejob?

do{

}while(condition);The loop works very much the same as that of the while loop.


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This will print the message once as the condition checking is done after

the loop is executed Had it been a while loop then the message would


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the loop is executed. Had it been a while loop then the message would

not have been printed at all.

Okay! The mantra is Use a for loop for finite iterations, awhile loop when number of iterations are not known and a dowhile loop if the loop has to be executed at least once.


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Arrays are collections of homogenous elements in

Chapter 9: Arrays

Chapter 9: Arrays


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continuous locations of memory having the same name.

Why arrays?

Most of the C application require the processing of large number of

data. The data may be identical and to be stored in sequential memory

location. So we share same name to to point a set of identical data. So

array is a collection of similar elements. these similar elements may be

int, char etc.

Three words- homogenous elements, continuouslocations and same name I'll remember that!

Chapter 9: Arrays

Chapter 9: Arrays

Array Declaration


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Like any other variable array need to be declared.

eg: int marks[60];

char message[40];

int specifies the type of variable stored in the array marks. 60 tells thecompiler the number of elements to be stored in the array.

note:- Compiler never gives error if you enter more than 60 elements in

the array. However, elements may go into the memory area notreserved by compiler for the array. This may cause data corruption . So

a proper check must be put in the program so that user may not enter

data more than the maximum specified limit.

Chapter 9: Arrays

Chapter 9: Arrays

Accessing Array element


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All the array element are given a label starting from 0. marks[0]

specifies the first element stored in the array. Similarly marks[20] is

the twenty-first element of the array. Thus the same variable namehave different content depending on it's label.

Entering Data into an Array

for (i=0;i


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times each time storing an element into the array.

note: We need not go for reading marks[60] as it will go out of bound.

Array initialization

note: In initialization, declaring the size of the array is optional.

If a array element is not initialized, it carries garbage value.

int number[5] ={1,2,3,4,5};

int n[]={1,2,3};

Chapter 9: Arrays

Chapter 9: Arrays

As soon as array is declared, compiler allocates the space to the array.

E h h i i dd h i l l i


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Each memory space has its unique address where a particular value is

stored.

An Example

Write a program to read marks of 60 student in the class and calculate

the class average.

main()

{

float avg, sum=0;

int i, marks[60];

Chapter 9: Arrays

Chapter 9: Arrays

for (i=0;i


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{

printf("\n Enter marks");

scanf("%d", &marks[i]);}

for (i=0;i


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A m*n array can be thought of with m rows and n column so as to keep

track of values in the tabular form.

for example: A two dimensional array containing float type data withmaximum 10 rows and 10 column can be declared as

float table[10][10];

note: This table may contain a maximum of 100 element, though the

compiler will not complain if you enter more than 100 element but this

may lead to data corruption. So a check on upper limit must be there in

the program.


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Chapter 9: Arrays

Chapter 9: Arrays

scanf ("%d", &n);printf("enter first matrix ");

f ( i i 0 i i )


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for ( int i=0;i


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note: A two dimension array can be read or written out using two

nested loop. In the above example, inner loop causes one row to be read

from the user while outer loop and outer loop controls the rows.In printing the matrix after adding ,we are changing line after

each row so as to give tabular look.

I can have arrays three dimensions too, but two itself iscomplex enough!

Chapter 9: Arrays

Chapter 9: Arrays

Arrays and Strings


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Arrays and Strings

Strings or simply any text are nothing but one dimensional array of

characters. Each character within the string will be stored within oneelement of the array.

eg:char text[] = "electronics";

There are 12 element in this array , 11 for the word and 1 for null

character(\0) which is added automatically at the end of the string.

There are different library function under the header file string.h which

processes the string.

Chapter 9: Arrays

Chapter 9: Arrays

for example:

strlen(s) will return the number of character in the string.


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( ) g

strcpy(s1,s2) copy string s2 to string s1.

The bottomline is character arrays have a terminator at theend.


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What are functions?

What are functions?


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Every C program is a collection of functions. Even main() is a function.

Program execution always begins with main().

A function is a set of instructions that does something.

Why functions?

i) Writing function avoids rewriting the same code over and over again.

Suppose it is required to find the number of ways of choosing r element

out of n element (i.e. n! / r! * (n-r)!). For this finding the factorial 3times is a tedious job. So it would be preferable to jump to factorial

subprogram three times and return to the main program.



ii) Functions help us to organize our work very well and keep track of

what we are doing. This way the work can be divided into separate

ll d l ll d f ti d th bi d t th


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smaller modules called functions and then combined together.

Example:

#include

void test();void again();

main()

{

printf ("\n Hello! I am in main");test();



again();

test();


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{

printf ("Are you there");}

void again() {printf ("I'm here again");

}

}

void test()

Output:

Hello! I'm in main.



Are you thereI'm here again


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I m here againAre you there

Explanation: void test(); and void again(); are the function prototypes

or declarations so that the compiler knows that these functions are

going to come later in the program. void specifies that function returnsnothing to the place where it is called.

test(); and again(); are the function calls.

void test() and void again() are the function headers from where the

function definition starts.



A function has a name, return type and a set of argumentsand arguments are optional


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g p

Function arguments and ReturnLet's see a function call avg = calavg(a,b,c);

On calling this function in main, function will return and assign

average of three numbers a, b, c to the variable avg. a, b, c are thefunction arguments and are called actual arguments.

Function can be defined as:-

float calavg( int x, int y, int z){

return (x+y+z) / 3; }



x, y, z are the formal arguments. Actual arguments and formal

t b th Th t t t t t th l


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parameters may be the same. The return statement returns the value

following it to the calling program. float specifies the type of value thatis to be returned by the function.

Chapter 11:ADVANCED CONTROL CONSTRUCTS


S t l t t


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Some more control constructs-

goto,continue,break statements

Some more control constructs-

goto,continue,break statements

Let's revise and add some more to what we have alreadyl t




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learnt.

The do-while statement

Sometimes it is required to execute the loop at least one time, we use do-

while loop.

example:

do {

..........(do some computation)printf("Do you want to continue the computation. enter y for

yes");



scanf("%c", ch);

} while ( ch = ='y');


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Again and again this message comes on the screen till youenter 'y' and at least one time the computation will go on

with this message.switch statement

In order to avoid the great size of if else statement, we use

switch statement. The general form is :

switch (expression)

{ case expression 1: statement;

..........

case expression m: statement; }



note: expression must result to only either integer or character type.

example:


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example:

switch (grade) {

case10: printf ("excellent"); break;

case 9:

case 8: printf ("good"); break;case 7:

case 6: printf ("average"); break;

case 5:

case 4:case 3:



case 2:

case 1:

case 0: printf ("improve"); break;


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p ( p ); ;

default: printf ("Wrong entry");

}

break statement is used so that control comes out of the switch block orany other block under braces {}where it is used.

note: If your grade is 9, then control flows from case 9: to case 8:

statement and a message good comes on screen.



The continue statement


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As the continue statement is met ,the next part of the loop is skippedand computation proceeds directly to the next pass through the loop.

for example:

for ( i =1; i


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goto statement



goto statement transfers the control from one part to any other part of

th H f t h ld b id d


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the program. However, use of goto should be avoided.

note: If the condition is satisfied the goto statement transfers control tothe label msg causing printf() following msg to be executed.

example: if (ans= = 5) goto msg;

............................

............................

msg: printf ("With good programming skills use of goto canalways be avoided");

Chapter 12: STORAGE CLASS AND SCOPE RULES



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Auto,static and extern variablesAuto,static and extern variables

Lifetime and scope of these variablesLifetime and scope of these variables



Storage class refers to the visibility of a variable and its scope within

the program i e the portion of the program over which the variable is


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the program i.e. the portion of the program over which the variable is

recognized. There are four different storage class in C: automatic,external, static and register which are identified by the keywords auto,

extern, static and register respectively. They are classified depending on

the following four parameters:

1)storage: where these variables are stored.

2)default initial value: value assigned to the variable at the time of

declaration.

3)scope: refers to the portion of program over which the variable isrecognized.

4)life: how long would the variable exist.



STORAGE

CLASS

STORAGE DEFAULT I

NITIAL

VALUE

SCOPE LIFE


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auto memory garbagevalue

local tothe block

where it is

defined

till the controlremains within the

block in which the

variable is defined.

register CPU

registers

(fastest

memory)

garbage

value

local to

the block

where it is

defined

till the control

remains within the

block in which the

variable is defined.



STORAGE CLASS STORAGE DEFAULT

INITIAL

VALUE

SCOPE LIFE


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static memory zero local to theblock where

it is defined.

value ofvariable

persists

between

differentfunction

calls.

extern memory zero global throughout

theprogram

note: Default storage class for a variable is auto.



Variables declared have a certain scope I see or maybe I


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can't see!!



Local Variables

The variables declared within the function are called local variable


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because scope of these type of declaration of variable only exist to the

function in which they are defined. The local variables are declared at

the start of function body.

Example: int sum(){

int x, y, s;.............}

int difference(){

int x, y, s;

..............}

The variables x,y,s which are declared in both the functions are local

and have different memory allocation. They have no relation among

themselves.



Global Variables

Th f l b l i bl i h h h Al


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The scope of global variable remains throughout the program. Also,

they hold their values during the entire execution of the program.

Global variables are always declared outside of all functions.

It is used when a variable must be accessible to more than one

function. However, external variables create organizational problem

for the very reason that they can be accessed by any function. The

wrong function may access them or function may access them

incorrectly.

Global variables I can always see, local variables I can seeonly within the local block0

Scope rules of functions

By default the scope of a variable is local to the function in which it is




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By default the scope of a variable is local to the function in which it is

defined. Hence a variable defined in main() is local to the main()function and similarly a variable defined in a subprogram has to be

returned to make it available in the calling function.

Chapter 13: ADVANCED FUNCTIONS


Methods of parameter passing

Methods of parameter passing


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Call by valueCall by value

Call by referenceCall by reference

Functions and arrays

Functions and arrays



Now that we have seen functions and their usage, let us look into the

various concepts

B f d t th i t t t l t d t d


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Before we proceed to these important concepts, let us understand

something about the function. A function is only a set of instructions

and the function name is a pointer to the start of the instructions which

make the function. So when a function is called, the control switches

from the caller function to the called function. After the function is

executed the control returns back to the caller.

There are two ways of passing parameters: 1.call by value and 2. call by

reference.

13.1 Methods of parameter passing

13.1 Methods of parameter passing



In the first method value is passed to a function via actual argument

13.2 Call by value

13.2 Call by value


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In the first method value is passed to a function via actual argument.

Value of actual argument is copied into the formal argument in the

function. Therefore, the value of corresponding formal arguments can

be altered within the function but the value of actual argument within

the calling routine will not change.

Example: main(){

int x=10, y=20;

swap(x,y);

printf("\n x=%d y=%d", x, y);}swap( int a, int b){

int temp;a=b;



printf("\n a=%d b=%d", a, b);}

output: a=20 b=10

x 10 y 20

b=temp;


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x=10 y=20

note: The value of x and y remain unchanged even after exchanging the

value of a and b.

13.3 Call by reference13.3 Call by reference

In the second method (call by reference), the addresses of actual

arguments in the calling function are copied into formal arguments of

the called function. This will facilitate the programmer to access the

actual arguments and hence will be able to manipulate them. Addressesof the actual argument are sent from the calling program through

address of or & operator while they are received in the called function

by the pointer variable.



13.4 Functions and arrays

13.4 Functions and arrays

The entire array can be passed to a function as an argument


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The entire array can be passed to a function as an argument.

Example:

float avg (int , int []); //function prototype

main(){

int x, lot[100]; float average;

...............

average= avg (x, lot); //function call

...............}

float avg (int n, int a[]) //function definition

{....................}



Explanation: When declaring a one-dimensional array as formalargument the array name is written as pair of empty square braces

while the size must be declared in the main function at the time of


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declaration. To pass an array to a function the array name must appearby itself, without bracket, as actual argument within the function call.

argc and argvThe arguments that we pass on to main() at the command prompt are

called command line arguments. The function main can have two

arguments, argc and argv. Out of these argv is an array of pointers to

strings and argc is an integer whose value is equal to the number of

strings to which argv points. When the program is executed the string on

the command line are passed to main(). More precisely the string at

command line are stored in memory and addresses of first string is

stored in argv[0] , and so on.



If I pass the value to the function , I am doing it by call by value, and If I

pass the addresses of the arguments I am going for call by reference.Can

we have the advantages and disadvantages please?


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Call by value:

Advantages: 1. Simple mechanism 2. Used in calling functions with few

argumentsDisadvantages: Memory wastage as the variables are duplicated

Call by reference:

Advantages: 1. Used when one need not return a value or indirectly

return more than one value2.Useful in passing arrays

Disadvantages: More complicated than the previous mechanism.

Chapter 14: RECURSION


Define recursion

Define recursion


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An example showing the working of recursive processAn example showing the working of recursive process



14.1 Define recursion

14.1 Define recursion


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Recursion is a low level feature of the 'C' language. It is a verypowerful mechanism of doing complicated programs and reducing the

size of the programs.

Recursion is a process by which the function calls itself repeatedly

until some specified condition has been satisfied. Also referred to as'circular definition', recursion is thus the process of defining ion terms

of own self.

Conditions that are to be satisfied for a recursive problem:

The problem must be written in recursive form.

The problem statement must include a stopping condition.



For example: In recursive form n! = n * (n-1)! and stopping condition is

1! = 1.


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Calculating Factorial of number n

#include

long int factorial(int n);

main()

{

int n;

printf(" \nEnter the number whose factorial is to be calculated\n");

scanf("%d", &n);

Example showing the working of recursive process

printf("n! = %ld\n", factorial(n));

}

long int factorial(int n)




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{if (n


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Chapter 15: POINTERS


What are pointers?

What are pointers?

Pointer Arithmetic

Pointer Arithmetic


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Arrays and PointersArrays and Pointers

ExercisesExercises

Array of PointersArray of Pointers

Pointers and stringsPointers and strings

Two dimensional arrays and pointersTwo dimensional arrays and pointers



What is a Pointer?

o A pointer is a variable which contains the address in memory of

another variable. We can have a pointer to any variable type.


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o Pointers are basically the same as any other variable. However,

what is different about them is that instead of containing actual

information, they contain a pointer to the memory location where

information can be found. This is a very important concept, andmany programs and ideas rely on pointers to be able to carry out

their tasks, linked lists for example.

o So what is a pointer? A pointer is a way to get at another object.Essentially it is a way to grab an instance of an object and then

either pass that instance a message or retreive some data from that

object.



oA pointer is actually just an address of where an instance is held in

memory.

The unary or monadic operator & gives the ``address of a variable''.


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The indirection or dereference operator * gives the ``contents of an

object pointed to by a pointer''.

To declare a pointer to a variable do:

int *pointer;

note: We must associate a pointer to a particular type: You can't

assign the address of a short int to a long int, for instance.



It is worth considering what is going on at themachine levelin memoryto fully understand how pointer work. . Assume for the sake of this

discussion that variable x resides at memory location 100, y at 200 and

ip at 1000. Note A pointer is a variable and thus its values need to be


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stored somewhere. It is the nature of the pointers value that isnew.Pointer, Variables and Memory Now the assignments x = 1 and y = 2

obviously load these values into the variables. ip is declared to be a

pointer to an integer and is assigned to the address of x (&x). So ip gets

loaded with the value 100.

Next y gets assigned to thecontents ofip. In this example ip currently

points to memory location 100 -- the location of x. So y gets assigned to

the values of x -- which is 1.


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So ...int *ip; *ip = 100;

will generate an error (program crash!!). The correct use is:

i *i


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int *ip;

int x;

ip = &x;

*ip = 100;

We can do integer arithmetic on a pointer:

float *flp, *flq;

*flp = *flp + 10;

++*flp;



(*flp)++;flq = flp;

note: A pointer to any variable type is an address in memory -- which is

i t dd A i t i d fi it l NOT i t D t i t d


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an integer address. A pointer is definitely NOT an integer.Data is storedin memory like this :

The reason we associate a pointer to a data type is so that it knows how

many bytes the data is stored in. When we increment a pointer we

increase the pointer by one ``block'' memory.So for a character pointer ++ch_ptr adds 1 byte to the address.

For an integer or float ++ip or ++flp adds 4 bytes to the address.

Consider a float variable (fl) and a pointer to a float (flp)

Pointer Arithmetic Assume that flp points to fl then if we increment thepointer ( ++flp) it moves to the position shown 4 bytes on. If on the other

hand we added 2 to the pointer then it moves 2 float positions i.e 8 bytes

as shown in the Figure.

Chapter 16: STRUCTURES


What are Structures?

What are Structures?
http://../meenakshy%20system%20backup/content%20files/cpage16.jsp


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Referencing elements of a StructureReferencing elements of a Structure

Pointers to StructuresPointers to Structures



Structures are collections of heterogenous elements in continuous

locations of memory having same name.

H ! Thi d i il !
http://../meenakshy%20system%20backup/content%20files/cpage16.jsp


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Hey! This sounds very similar!

Structures are different from arrays only with respect to the type of

elements, ie. homogenous in case of arrays and heterogenous in case of

structures.

Why structures?

An ordinary variable can store one piece of data and an array can store

large number of data but of same data-type. Structure is the data typewhich can store large number of data of different data type. Suppose in

a class there are 60 student, you want to store the name (string), age

(integer), marks (integer) of each student.



This can be done by defining structure variable as follows:struct class

{

char name[20];

int age;


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int age;int marks;

};

struct student[60];

Now each array element student[i] has memory space corresponding to

three variable name, age and marks.

note: To declare a structure the above group of statement is used. If

you want to add more element to the structure you can very well do it.

Always declare structure outside main() above main().


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student[1] = student [2]; is same as

student[1].name = student[2].name;

student[1] age = student[2] age;


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student[1].age = student[2].age;

student[1].marks = student[2].marks


Chapter 1

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