c entire notes

7/31/2019 C Entire Notes

1/127

A Course on REAL-TIME EMBEDDED SYSTEMS

. . . by Krest Technologies

----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------

Head Office: II Floor, Solitaire Plaza, Near Image Hospitals, Ameerpet, Hyd.

Branch Office: #310, Sreemaan Rama Towers, Opp. Kalaniketan, Chaitanyapuri, Dilshuknagar, Hyd.

E-mail:[email protected], Web: www.kresttechnology.com

Presents

A Module

on

C - PROGRAMMING


2/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




C

Program is set of instructions, these instructions are executing by the system, that system

is providing result.

Ken Thomson developed BCPL (Basic Combined Programming Language) programming

language. This programming is difficult to learn and execute. His co-programmer Dennis Ritche

was introduced a programming called C. Is from Bell Laboratories in 1972.

Here is nothing, in BCPL from second letter C Combined programming language.

It is high level structured programming language.

Every Program must have one main () function. This section contains two parts:

1) Declaration Part 2) Executable Part.

The Declaration part declares all the variables used in the executable part. There is at least

one statement in the executable part. These two parts must appear between the opening and

closing braces. The Program execution begins at the opening brace and ends at the closing brace.

All statements in the declaration and executable parts ends with a semicolon.

The Sub Program section contains all the user defined functions that are called in the main

function.

Executing a C Program:

The Steps involved in executing a C Program are:

1. Creating the Program.2. Compiling the Program.3. Linking then Program with function that is needed from C Library.4. Execute C Program.

Basic Structure of C Program:

Documentation Section - suggestion

Link Section - optional

Definition Section - optional

Global Declaration Section - optional


3/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




The Documentation section consists of a set of comment Liner giving the name of the Program

the author and other details. Which the Programmer would like to use Later.

The Link section Provides instructions to the compiler to link functions from the system Library.

The Definition section defines all symbolic constants.

There are some variables that are used in more than one function such variables are called global

variables and declared in the global declaration section i.e., outside of all functions.

Getting Started with C:

There is a Close analogy between learning English Language and learning C

Language. The Classical method of learning English is to first learn the alphabets or characters

used in the language, then learn to combine these alphabets to form words. Which in turn are

combined to learn sentences and sentences are combined to form paragraphs. Learning C is

much similar and much easier.

Like English to learn C. We must first know what alphabets, numbers and

special symbols are used in C, then how using these constants, variables and keywords are

constructed, and finally how are combined these to form an instruction. A group-s of

instructions would be combined to form a program.

Steps in Learning English Language:

Alphabets----->Words------>Sentences----->Paragraph

Steps in Learning C:

Alphabets, Constants

Main () function section - necessary

{

Declaration Part

Executable Part}

Sub Program Section

Function 1

Function 2

Function 3


4/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




Digits, -------> Variables ------> Instructions ------>Program

Special Symbols Keywords

Character set Tokens

The C Character Set:

The C character denotes any alphabet, digit or special symbol used to represent information.

Alphabets A,B,C,..Y,Z.

a,b,c.y,z.

Digits 0,1,2,3,4,5,6,7,8,9

Special Symbols {, }, [,], (, ) , !,

C Tokens:

The smallest individual units in a C Program are Known as C Tokens.

C Tokens

Keywords Constants Variables

C Keywords:

Keywords are the words whose meaning has already been explained to the C compiler.

The keywords cannot be used as variable names because if we do so we are trying to assign a

new meaning to the keyword, which is not allowed by the computer. The keywords are also

called Reserved words. Keywords serve as basic building blocks for program statements.All

keywords must be in lowercase letters. Some compilerws may use additional keyword that must

be identified from the manual.

There are only 32 keywords available in C. Following is the List of keywords in c.

Auto double int static

Break else long struct

Case enum volatile switch

Char extern register type def


5/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




Const float return union

Continue far short unsigned

Default go to signed void

Do if size of while

Constants:

A constant is a fixed value that do not change during the execution of a Program for

example in the equation

3x+y=20

Since 3 and 20 cannot change, they are called constants, where as the quantities x&y can vary or

change hence are called variables.

Constants

Numeric constants

Character constants

Integer constants

Real constantsSingle character constants

String constants

Integer Constants:

An integer constants refers to a sequence of digits. There are 3 types of integers

namely decimal, octal and hexadecimal.

Decimal integer constants of set of digits, 0 through 9, preceded by an optional or + sign.

Eg: 123

-321

+78

0

An octal integer constants consists of any combination of digits from the set 0 through 7

with leading 0.

Eg: 037

0435


6/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




0551

0

A sequence of digits preceded by 0x or 0x is considered as hexadecimal integer. They may also

include alphabets A through F or a through f. The Letters A through F represents the numbers 10through 15.

Eg: 0x2

0x9f

0xbcd

0x

Rules for Constructing Integer Constants:

1) An Integer constant must have at least one digit.2)

It must not haver a decimal point.

3) It could be either positive or negative.4) If no sign preceds on integer constant it is assumed to be +ve.5) No commas or blanks are allowed within an integer constant.6) The allowable range for integer constants is -32768 to 32767.

Real Constants:

Integer numbers are inadequate to represent quantities that vary continuously. Such as

distances, heights, temperatures, prices and so these quantities are represented by numbers

containing actional parts like 17.548. Such numbers are called real or floating point constants.

Eg: 0.0083

-0.75

435.36

247.0

A real number may also be expressed in exponential (scientific) notation. The general form is

Mantissa e exponent

The mantissa is either a real number expressed in decimal notation or an integer. The exponent is

an integer number with an optional plus or minus sign. The letter e separting the mantissa and

the exponent can be written in either lowercase or uppercase.

Eg: 0.65e4

12e-2

3018e3

-102e-1

For example the value 215.65 may be written as 2.1565e2 in exponential notation. E2 means

multiply by 102.


7/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




Rules for constructing Real Constants:

Following rules must be observed while constructing real constants expressed in fractional

form.

1) A real constant must have at least one digit.2) It must have a decimal point.3) It could be either positive or negative4) Default sign is positive.5) No commas or blanks are allowed within a real constant.

Following rules must be observed while constructing real constant expressed in exponential

form:

1) The mantissa part and the exponential part should be separated by a letter e.2) The mantissa part may have a positive or negative sign.3) Default sign of mantissa part is positive.4) The exponent must have at least one digit which must be a positive or negative.

Default sign is positive.

5) Range of real constants expressed in exponential form is -3.4e38 to 3.4e38.

Character Constants:

There are 2 types of character constants.

1) Single character constants 2) String constantsSingle Character constants:

A character constant is either a single alphabet, a single digit or a single special

symbol enclosed within single inverted commas.

The maximum length of a character constant can be 1 character.

Eg: A , 1, 5, =

String Constants:

String constant is a sequence of characters enclosed in double quotes. The characters

may be letters numbers, Special characters and blank space.

Eg: Hello!, 2005, Well Done, ?, T


8/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




Variables:

Variable names are names given to locations in the memory of computer where different

constants are stored. These locations can contain integer, real or character constants, unlike

constants the variables remains unchanged during the execution of a program a variable may

take different values at different times during execution.

Rules for constructing variable names:

1) A variable name is any combination of 1 to 8 alphabets, digits or underscores. Somecompilens allow variable names whose length could be up to 40 characters.

2) The first character in the variable name must be an alphabet.3)

No commas or blanks are allowed within a variable name.

4) No special symbol other than an underscore can be used in a variable name.A variable name can be chosen by the programmer in a meaningful way so as to reflect its

function or nature in the program.

Eg: average, Height, Total, Counter-1, Class-strength

The data value stored by a variable can be of integer, float, real number or character constant. So

the variable is declared with a data type depending on the type of the data value each data item

in a c Program related with a type known as data type.

Declaration of variables:

The declaration of variables must be done before they are used in the program variable

declaration does there things.

1) It tells the compiler what the variable name is.2) It specifies what type of data the variable will hold3) What set of operations that are performed against this location.

The syntax for declaring a variable is as follows:

Data type v1, v2, . vn;

V1, v2,.vn are the names of variables. Varaibles are separated by commas. A declaration

statement must end with a semicolon.

Eg: int count;

int number, total;


9/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




Double ratio;

Assigning values to variables:

1) Values can be assigned to variables using the assignment operator = as follows.Variable name = constant;

Eg: a = 10;

B = 20;

Balance = 75.84;

ANSI C supports four classes of data types.

1) Primary dat types2) User defined data types3) Derived data types4) Empty data type.2) C point multiple assignments in one line.

Eg: a = 10; b = 20;

3) It is also possible to assign a value to a variable at the time the variable is declared.The general form is

Data type variable-name = constant;

Eg: int a =10;

Char ch =x;

Double balance = 75.84;

4) The process of giving initial values to variables is called initialization C permits theinitialization of more than one variables in one statement using multiple assignment

operations.

Eg: p = q =s =0;

X =y =z =max

The first statement initializes the variables p,q and s to aero, while the second initialize x,y and z

with max.

Note that max is a symbolic constant defined at the beginning.

Operators :-


10/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




Operator is a symbol it can operate the two or more operands.

1) Arithmetic operator :-It is used to construct the mathematical expressions as in algebra. +, - *, / , %

a+b , a-b, a/b, a*b, a%b = reminder value

2) Relational operator :- to compare the two quantities.=, = =, !=

a>b a>=b a logical OR, ! -> logical NOT4) Assignment operators are used to assign the value of an expression to a variable. =.

V = exp or value;

a = 10; or a= b + c;

5) Increment ++ operator is to adds 1 to the operand while Decrement -- operator is tosubtracts 1.

Pre post

++ a a++ = a=a+1

--a a- - = a= a-1

6) Conditional operator ? : is a ternary operatorexp1 ? exp2 : exp3 ;X= (a>b)? a is big : b is big ;

7) Bit wise operators are for manipulation of data at values of bit level. These are used fortesting the bits or shifting them to the right or left.

&,!, ~, ^,

8) Special operators of interest for sizeof(), typedef(), *(pointer), this operator, arrow ()operator

Input/ Output functions :-

To read the data from the key board, and to print the data on screen using the I/O functions.

1. Character I/O functions2. String I/O functions3. Formatted I/O functions


11/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




1. Character I/O functions :-getchar( ):- to read the single character from the key board.

x=getchar( );

putchar( ):- to write the single character on the screen.

Putchar(x);

2. String I/O functions:-gets( ):- to read the string(group of characters).

x=gets();

put( ):- to write the string.

puts(x);

getch( ):- is a reading function, but it cant print the value.

getche( ):- is a reading function, it can print the value. Ex:- k it can print the k.

3. Formatted I/O functions:-scanf ( ):- to read any type of data, means int, float, char, string and double

scanf(controle string,&v1,&v2


12/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




Decision Making Statements (We are calling Control statements.)

If statements Switch statements

Conditional operator statements.IF Statement :-

If statement is a powerful DMS and is used to control theflow of executing statements. It is a two-way decision statements

and is used in conjunction with an expression.

if ( test expression)

Example :-

if ( age > 58)

{

Printf(Employee is retired );

}

Simple if statement :- here the condition is checks first, if it is true execute the body statements,

O.w another stmts are execute.

Syntax :-

if (test exp)

{

statement block;

}

Statement x;


13/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




Program:-

#include

#include

Void main()

{

int age;

printf(enter the age);

scanf(%d,&age);

if(age> 58)

{

Printf(the employee is retired):}

}

If else: - Here the condition is checks first, if it is true execute the body statements, if it is

false execute the else part.

if (test exp)

{

statement x;

}

else

{

statement y;

}

Statement z;

#include

#include

Void main()

{

int age;

printf(enter the age);

scanf(%d,&age);

if(age > 18)


14/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




{

Printf(the preson is major);

}

else

{

Printf(the preson is minor);

}

getch();

}

Nested if :- here the condition is checks first, if it is true, again it checks the within the condition,it is true then execute the body stmt, or else stmt, or outer if else part will be execute

if (test exp)

{

if(test exp)

{

statement x;

}

else

{

statement y;

}

}

else

{Statement z

}

Statement x;

#include

#include

Void main()

{

int a,b,c;


15/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




printf(enter the a b c values);

scanf(%d%d%d,&a,&b,&c);

if(a > b)

{

if(a>c)

{

printf( a is big);

}

else

{

Printf( c is big);

}

}

else

if(b>c)

{

Printf( b is big);

}

else

{

Printf( c is big);

}getch();

}

Else if or Ladder if :- here the condition is checks first, if it is true execute the body statements,

o.w it can false it will checks the another else if stmt and so on.. up to the conditions are true.


16/127


17/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




}

Else If( choice==2)

{

Printf(the color is Orange);

}

Else If( choice==3)

{

Printf(the color is Yellow);

}

Else If( choice==4)

{

Printf(the color is Green);}

Else If( choice==5)

{

Printf(the color is Blue);

}

Else If( choice==6)

{

Printf(the color is Indigo);

}Else If( choice==7)

{

Printf(the color is Violet);

}

Else

Printf(you choice is invalid number );

getch();

}

Switch statement:-

The switch stmt tests the value of a given variable against a list if case value and when amatch is found, a block of stmt associated with that case is executed.


18/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




Switch(v or exp)

{

case 1: stmt 1;

break;

case 2: stmt 2;

break;

default: stmt x;

}

Program to print the different colors.

#include

#inlude

Void main()

{

int choice;

Printf(enter the choice);

Scanf(%d,&choice);


19/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




Switch(choice)

{

case 1:

Printf(the color is Red);

break;

case 2:

Printf(the color is Orange);

break;

case 3:

Printf(the color is Yellow);

break;

case 4 :Printf(the color is Green);

break;

case 5:

Printf(the color is Blue);

break;

case 6:

Printf(the color is Indigo);

break;

case 7:Printf(the color is Violet);

break;

default :

Printf(you choice is invalid number );

getch();

}

Decision Making Looping Statements :-

A statement is executing more than one time with in the condition.

1. Entry level looping stmt

2. Exit level looping stmt

We have 3 looping statements are there,

1. While2. Do while3. For loop


20/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




1. While : it is an entry level looping statement and first test the condition, it can be truethen execute the body of the loop statements up to the given condition is false, if not

execute the out of the body statements.

Initialization;

While(condition)

{

Body of the statements;

Increment/ decrement stmt;

}

Program to print the math table.

#include

#include

Void main()

{

Int a,i=1;

Printf(enter the a value);

Scanf(%d,&a);

While(i


21/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




Program to print the math table.

#include

#includeVoid main()

{

Int a,i=1;

Printf(enter the a value);

Scanf(%d,&a);

do {

C= a * i;

Printf(\n%d %d = %d,a, i, c);

i=i+1; // i++; // i+=1;} While(i


22/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




Nestedforloop:-

A loop statement is executed within the another looping is called nested loop.

for(init; test-condition 1; incr/decr)

{

for( init ; test-condition 2 ; incr/decr)

{

Body of the loop;

}

}

Program to print the multiple math table.

#include

#include

Void main()

{

int a,i;

Printf(enter the a value);Scanf(%d,&a);

for(a=1;a


23/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




Arrays and Strings :-

Array is similar type of data collection name.

It is a collection of same data type elements. An array is a group of related data items, whichshare common name. it is a set of homogeneous data.

Ex:- in a class room if 30 students are there, they have snos, names we declare 30 variable, some

it is not possible so we are rectifying this problem using an array.

Types of Array:

1. Linear Array2. Non Linear Array

Linear Array:- This type of array is also called One dimensional array. This is also called listarray. in this array only one subscript is used. It is written either in row or in column form.

Syntax:- datatype arrayname[size];

Where data types are int, float or char.

Array name is any name or word or character.

Ex:= int a[20];

Float sal[10];

Char name[20];

Size should be one cell more than the given data length, because last cell should be empty or null

cell that is the end of the string has null character.

Char name[10];

K e e r t h i

0 1 2 3 4 5 6

int a[5];

a[0]=20, a[1]=30, a[2]=40, a[3]=50, a[4]=60.

Assigning Values to an array:-

Data type arrayname[size]={list of values};

Int a[5]={4,5,6,7,8,9};

To read and print the single dimensional array elements


24/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




#include

#include

Void main()

{int a[5],i;

Printf(enter the a values);

for(i=0;i


25/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




2. Three dimensional array:- called space array. in this space, row and column are taken.These are also called xyz array.

int a[2][2][2];

a[0][0][0], a[0][0][1], a[0][1][0], a[0][1][1], a[1][1][1];

To read and print the two dimensional array elements

#include

#include

Void main()

{

int a[5][5],i,j;

Printf(enter the a values);

for(i=0;i


26/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




Strings :-

More than on character is string. Group of characters is a string.

I LOVE INDIA

Printf( I Love India);

But if the string is stored in variable, then such type of variable should be of character type. Also

character variable should be declared in the array form (one dimensional array)

data type arrayname[10];

Char name[10];

Printf(%S, name);

Char name*10=k,e,e,r,t,h,i};

Multiple string

Char name[4][10];

for(i=0;i


27/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




Strcmp :- this is to compare two strings. It will check which string is alphabetically above the

other.(ASCII) values are used.

Strcmp(string1,string2)

Strcpy :- this is to copy one string into another string. Note that, destination field should be

larger than the source filed. In other words size of the string1 should be larger to receive the

contents of the string2.

Strcpy(string1,string2)

Printf(%s, string1);

Strlen :- is to count the number of character in a string, to find the length of the string.

n = strlen(string1);

printf(%d,n);

strrev : - is to reverse a string. This function takes string variable as its single argument. here the

first char becomes last and last becomes first in a string. This is to find string palindrome or not

madam .

strrev(string1)

Program On String Functions

#include

#include

Void main()

{

char a[10],b[10];

int n;

printf(enter the string a,b);

gets(a); // scanf(%s,&a); // scanf(%c,&a*i); here i is define

gets(b);

n = strlen(a);printf(%d,n);

strcpy(a,b);

printf(%s,a);

strrev(a);

printf(%s,a);

getch();

}


28/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




Function:-

Definition

Function is block or part of program. When any program is very long or same code is

repeating many times then we try to cut the program in different parts (or blocks) so that whole

program became more understandable, easier to debug (error checking) and size of code will be

lesser.

Syntax of function in c programming

Data type function(parameters);

Or

Data type function(){

Statements x;

Statements-y;

-----------------

--------

}

Functions are dividing in to types

1. Function no arguments and no return type2. Function with arguments and no return type3. Function with arguments and with return type.

Simple example of function structure

intsum (int,int); //function declaration

voidmain()

{

int p;p=sum(3,4); //function call

printf(%d,sum);

}

intsum( int a,int b) //function definition

{

int s; //function body

s=a+b;

return s; //function returning a value

}


29/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




Detail explanation of syntax of function:

(1) Function_name :

Function naming rule in c programming:

Rule 1. Name of function includes alphabets, digit and underscore.

Valid name: world, addition23, sum_of_number etc.

Invalid name: factorial#, avg value, display*number etc.

Rule2. First character of name of any function must be either alphabets or underscore.

Valid name: _calulate, _5,a_, __ etc.

Invalid name: 5_, 10_function, 123 etc.

Rule 3. Name of function cannot be any keyword of c program.

Invalid name: interrupt, float, asm, enum etc.

Rule 4. Name of function cannot be global identifier.

Valid name: __TOTAL__, __NAME__ ,__TINY__etc.

Invalid name: __TIME__,__DATE__, __FILE__,__LINE__,__STDC__

Note: It is good practice to not write the variable name in the above format.

Rule 5: Name of function cannot be register Pseudo variables

Rule 6. Name of function cannot be exactly same as of name of other function or identifier

within the scope of the function.

Rule 7. Name of function is case sensitive.

Rule 8. Only first 32 characters are significant of the functions name.

Example: abcdefghijklmnopqrstuvwxyz123456aaa,

abcdefghijklmnopqrstuvwxyz123456bbb,

abcdefghijklmnopqrstuvwxyz123456cad

All three function name are same because only first 32 characters has meaning. Rest has not any

importance.


30/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




Return type of function in c programming

return is keyword of c. When the control reaches to the return keyword it immediately

terminates the execution of that function and transfer the control to the calling function.

Syntax of return statement:

Here expression is optional which has indicated by [ ].

Example:

voiddev();

voidmain()

{

clrscr();

printf("one\n");

dev();

printf("two\n");

getch();

}

voiddev()

{

printf("three\n");

return;

printf("four\n");

}

Output:

one

three

two

Return type of function can be:

1.Primitive data type.

Primitive data types are: char, int, float, double, void

Examples:

a. function which is returning char data type

b. function which is returning int data type

c. function which is returning float data type

d. function which is returning double data type

e. function which is returning void data type

2.Derived data type.
http://cfunction.blogspot.com/2009/05/function-which-is-returning-char-data.htmlhttp://cfunction.blogspot.com/2009/05/function-returning-int-data-type-in-c.htmlhttp://cquestionbank.blogspot.com/2009/05/function-which-is-returning-float-data.htmlhttp://cfunction.blogspot.com/2009/05/function-which-is-returning-double-data.htmlhttp://cfunction.blogspot.com/2009/05/function-which-is-returning-void-data.htmlhttp://cfunction.blogspot.com/2009/05/function-which-is-returning-void-data.htmlhttp://cfunction.blogspot.com/2009/05/function-which-is-returning-double-data.htmlhttp://cquestionbank.blogspot.com/2009/05/function-which-is-returning-float-data.htmlhttp://cfunction.blogspot.com/2009/05/function-returning-int-data-type-in-c.htmlhttp://cfunction.blogspot.com/2009/05/function-which-is-returning-char-data.html


31/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




Derived data types are: array, function, pointer

Examples:

a. Function which is returning array

b. function which is returning functionc. function which is returning pointer

3.User defined data type.

User defined data types are: structure, union, enum

Examples:

a. Function which is returning structure

b. Function which is returning union

c. Function which is returning enum

Feature of functions parameter in c

1.Default parameter of function is void.

2.Only register storage class is allowed with function parameter.

intdevD(registerint,registerint);

voidmain(){

int temp;

temp=devD(5,25);

printf("%d",temp);getch();

}

intdevD(intregister x,intregister y)

{

staticint num;

num=x+y+1;

return num;

}

Output: 20

3. Default storage class of function parameter is auto.4. If function declaration has not written then during the function call it doesnt check

prototype of function if function return type is int data type and parameter is not float

data type.
http://cquestionbank.blogspot.com/2009/05/function-returning-pointer-to-array-in.htmlhttp://cquestionbank.blogspot.com/2009/05/function-which-is-returning-pointer-to.htmlhttp://cquestionbank.blogspot.com/2009/05/function-which-is-returning-pointer.htmlhttp://cfunction.blogspot.com/2009/05/function-returning-structure-in-c.htmlhttp://cquestionbank.blogspot.com/2009/05/function-returning-pointer-to-union-in.htmlhttp://cquestionbank.blogspot.com/2009/05/function-returning-pointer-to-enum-in-c.htmlhttp://cquestionbank.blogspot.com/2009/05/function-returning-pointer-to-enum-in-c.htmlhttp://cquestionbank.blogspot.com/2009/05/function-returning-pointer-to-union-in.htmlhttp://cfunction.blogspot.com/2009/05/function-returning-structure-in-c.htmlhttp://cfunction.blogspot.com/2009/05/function-returning-structure-in-c.htmlhttp://cquestionbank.blogspot.com/2009/05/function-which-is-returning-pointer.htmlhttp://cquestionbank.blogspot.com/2009/05/function-which-is-returning-pointer-to.htmlhttp://cquestionbank.blogspot.com/2009/05/function-returning-pointer-to-array-in.html


32/127


33/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




RECURSION:

When called function in turn calls another function, then a process of chaining occurs

Main()

{

printf( krest);

main();

}

Recursion is a special case of this process or chain. So when a function calls itself, then it

is called recursion.

This chain continues till a specific condition met. If it has not any stop condition, then if will

create an infinite loop.

Recursion is used to solve for the problems, which cannot be solved by the iterative

procedure for, while and do loops. It is useful to solve repetitive problems, where input of

one sub program can be used as staring value having the previous output.

Condition:

1) A recursive function should have specific condition.

2) A recursive function should have smaller argument each time than the previous argument

value in the every recursive loop.

Factorial with recursion

main()

{

int n, fact();

printf(enter a value);

scanf(%d,&n);

Printf( %d factorial is %d,n,fact(n));

getch();

}

Fact(n)

Int n;

{

int m;

If(n==1)

{ return(n); }

else { m=n*fact(n-1); return(m); } }


34/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




Use of Array in function(Passing Array to function)

Array plays an important role in the function handling. Arraying are declared with the

function definition and so can be used in the function declaration stmt.

1) Passing one Dimensional array to fun:-

syn:- fun-name(array-name, array-size);

Ex:- sort(a,n); => an array defined as int a[20]; and n is size of array, n an array defined as int a[10][10]; and n is row size of array, n


35/127


36/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




Register int countr1, countr2;

Static storage class:It is a storage which is also quite similar to auto except that the variable once

defined any where do not die till program ends and the value of variable will also be

retained, but will be assessed only by the function declaring it. Static storage variables

have initial value is zero and not garbage. Static auto variable has a global lifetime and

local visibility. It cannot be accessed from another function.

Main()

{

fun();

fun();getch();

}

fun()

{

static int a;

a++;

printf(\n%d,a);

}

External storage classWhen there is a need for a variable to be assessed in all the functions in a c. the external

variables serve the purpose. Scope of the external variable is global. These variable are

assessed globally and has the initial value as zero and not the garbage value, so these

variables do not die at the start or at the end of any function program. But die at the end of

the whole program.

These are used to transfer the value from one function to another, their scope is from the

position of their declaration to the end of the program. Here no fresh memory is allotted.

int a;

main()

{

a=a+1;

printf(%d,a);

fun1();

fun2();

fun3();


37/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




fun4();

printf(%d, a);

getch();

}fun1()

{

a=a+10;

Printf(%d,a);

}

fun2()

{

a=a+5;

Printf(%d,a);}

fun3()

{

a=a-2;

Printf(%d,a);

}

fun4()

{

a=a-8;

Printf(%d,a);}

Out put :-

1 11 16 14 22 22


38/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




POINTERS :-

Pointers are memory address variable i.e the variables, which have address of the variable

having some value, stored in the memory, pointers are directly linked to the memory address.Actually pointer is a variable having address of another variable and not the value.

Variable name memory value memory address memory variable

q 280 6000 p

Here q is int variable having 280, is stored at the memory address 6000 this variable is

p(pointer).

P which is a memory variable and is stored further in the memory and again it has some memory

address. (Pointer to pointer).

Variable name memory value memory address memory variable

q 280 6000 p pointer

p 6000 5980 r pointer to pointer

Advantages:

1. Pointers increases the execution speed of the c-program and more efficient.2. Pointer reduces the length and complexity of the program.3. Pointer access the memory elements very easily.4. Use of the pointer to the character arrays are easier to handle and represent with the

pointers.5. Pointers have direct link with structure and union.6. Pointer saves the memory space. This can be done by using the dynamic memory

allocation technique.

Declaring a pointer variable

A pointer variable should be declared before they are used, similar to the common variable.

The pointer variable be declared in data type.

data type *pointer-variable;

Where data-type may be integer(int), float, char or double. Also here * (asteric sign)

means it is pointer operator and pointer variable is any variable linked with * sign. The symbol

* is called indirection operator.

int *x; float *y; char *z;

Note:- pointer are classified on the basis of its declaration. i.e whether a pointer variable holds

the address of an integer or a float or a char variable.

int *p, q;


39/127


40/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




p1 = &x;

p2 = &y;

z=(*p1) / (*p2);

a=(*p1) + (*p2);

b=(*p1) * (*p2);

c=(*p1) - (*p2);

int a,b, *p1,*p2;

b=280;

p1=&b;a=200;

p2=&a;

if(*p1>*P2)

{

stmts;

}

#include

#includeint *p1, *p2, *p3;

int i=1;

int j=2;

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

main()

{

int m,n,x;

p1=&j;

p2=&j;p3=&a[0];

m=p1-p2;

n=*p1+*p2;

x=*p3+2;

if(p1>p2)

printf(%d%d%d,m,n,x);

if(p1


41/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




Increment / Decrement operator the address pointer as :

p1 = p1 +1;

p1 = p1 1;

p1 ++;p1 - - ;

the statement p1++ will increment the address value in the pointer variable depending on

the type of the variable. If the pointer is of int type, then the pointer address is value will be

incremented by 2 and if it is of char type, then the value will be incre by 1; this increase or

decrease is according to cells in the memory and cells works according to the scale factor. Scale

factor is a scale or measurement of the length of the cells of different data type in terms in terms

of bits or bytes.

data type memory spacechar 1

int 2

float 4

double 8

note :-pointer can be incr /decred. These can not be arithmetic and logical and relational and

assignment operators

Pointer with array :-pointer have close relationship with array. an array name is in fact a pointer to the

array. pointer are linked with array by taking its first element number and its base address.

ststic int a[5]={23,24,25,26,27};

a[0] a[1] a[2] a[3] a[4]

23 24 25 26 27

1000 1002 1004 1006 1008

address of x[element no]= base address + element no. * scale factor

3rd element of the array and you have base address 100,

x[3] = 1000 + 3 * 2 = 1006

x[4] = 1000 + 4 * 2 = 1008

x[10] = 1000 + 0 * 2 = 1000

int a[5], *p;

p=a;

P=&a;


42/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




p=&a[0];

Above all are sameAddress value address value address value

&a[0] a[0] a+0 *a p *p

&a[1] a[1] a+1 *(a+1) p+1 *(p+1)

&a[2] a[2] a+2 *(a+2) p+2 *(p+2)

So on.

#include

main()

{ststic int a[5]={23,24,25,26,27};

int i, n, *p;

p=a;

n=5;

for(i=0;i0; --i){

printf(%4d,(a+i));

}

getch();

}

Type of array pointer:-

1) one dimensional array pointer:-

Is works according to the given base address, the number of elements in an array and thedata type of array.

#include

main()

{

int a[20], *p1, i, n, sum=0;

clrscr();

printf(\n enter the value of n:):

scanf(%d,&n);

printf(enter the array element);


43/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




for(i=0;i


44/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




concept, the names of the actual argument are used in the function call. So call by value of the

actual argument passed to the function.

Best explanation of call by value and call by reference can be done by taking the example ofswapping the numeric data..

Swapping:

Swapping is part of pointer as function argument. Swapping is the exchange of value

from one variable to another. We can say, if we take two variables x, y and we can exchange

value of x into y and y into x, then it is the process of swapping (or exchanging). We explain the

process of swapping by the following program:

Call By Value:

/*Program to illustrate the concept of call by value (argument passing without pointer)*/

main ()

{

int a,b;

a = 5;

b = 10;

printf(\n Value of a = %d and Value of b = %d before swap, a, c);

swap (a, b);printf(\n Value of a = %d and Value of b = %d after swap, a, b);

getch();

}

swap (int x, int y)

{

int temp;

temp = x;

x = y;

y = temp;

return;

}

The output is:

Value of a = 5 and Value of b = 10 before swap

Value of a = 5 and Value of b = 10 after swap


45/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




Call By Reference:

main ()

{

int a, b *aa, *bb;

a =5;

b = 10;

aa = &a;

bb = &b;

printf(\n Value of a = %d and Value of b =%d before swap, a, b);

swap(aa,bb);

printf(\n Value of a = %d and Value of b =%d after swap, a, b);getch();

}

Swap( int *x, int *y)

{

int *temp;

temp = x;

x = y;

y = temp;

return;}

The output is:

Value of a = 5 and Value of b = 10 before swap

Value of a = 10 and Value of b = 5 after swap

B) Pointer to function:

A function works like a variable. It has also similar dat type declaration like the othervariable. Pointer to a function variable occurs when you define a while function as pointer by

using . As function has address location in memory the syntax used to declare pointer to

function is as:

data-type (*function name)() ;

type (*fptr)( );


46/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




where type is the data type which may ne integer, float or character, fptr () is function name

and * (fptr) () is pointer to function. For example, the procedure to illustrate this concept is as

follows:

int mul ( ). (*p1) ( ):p1 = & mul ;

By using the above example, we can say that mul ( ) is a simple function. But p1 is

pointer variable which work as pointer to function and in second statement the address of the

mul ( ) function is assigned to p1 variable which is the memory variable and you know memory

variables or pointer. So p1 ( ) pointer function is linked to the function mul.

main( )

{

int mul ( ). (*p1)( ), x,y ,z;scanf (% d % d, & x, & y);

p1 = &mul ;

z =*p1 (x, y);

printf ( % d,z);

getche( );

}

mul (int p, int q)

{

int m ;

m = p * q;return (m);

}

POINTERS AND STRINGS:

Pointers plays an important role in inputting, outputting and processing the strings and

line of text. Pointers linked with array with two ways:

i) Array of pointers to stringsii) Passing array of strings to functioniii) An array of pointer to string can be declared as in the case of basic type variables.

This can be declared in terms of variable and constants. Two-dimensional arrays in

terms of pointer *t[20] and a[20][30] are defined.

This can be represented as:

Static char *t[20], a[20][30];

Unsigned int i;

For(i=0;i


47/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




}

This procedure completely states the definition of array of pointers to the strings. As the variable

a is itself an array of type char, so an array of pointers to strings t is an array of pointer to char.

For example, below is a c program illustrate the concept of array of pointer to string as:

1. Program to print the string cities and their addresses using array of pointer to the string

concept

main()

{

char city* = krest,ameerpet,dilsukhnager};

int i;for(i =0; i


48/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




Void pass (char **m, int n)

{

int i;

for (I =0; i


49/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




calloc():

The general syntax used is as:

Void *calloc(xyz, unsigned size);

The calloc() function provides dynamic allocation of block of consecutive memory

locations of size to xyz from trhe heap of the memory. It return a pointer to the newly allocated

block. If enough memory is not available, then NULL value be returned. Like in the case of of

malloc function the memory allocation pointer can be cast to the proper type.

realloc():

The general syntax used for this function is as:

Void *realloc(void *block, unsigned size);

It adjust the preciously allocated block to the size bytes. I will allocate the increasing or

decreasing the block to the new size. Here block refers to the original block already allocated by

malloc() or calloc() function. It returns the address of the new reallocated block. Note that if it

will unable to reallocate the block , then it will display and return the Null value. For example,

the concept of allocation of dynamic memory can be explained by using the c program as below:


50/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




STRUCTURE :-

We know different data type of variables can be used for different purpose. C support

such type of constructed data type, which is called Structure.A structure having different type of data types in a single structure.

A structure is Heterogeneous collection of related fields. Here fields are structured member

elements. A field has different data type.

For example, book having title, author, price, pages

Struct library

{Char title[20];

Char author[20];

Int pages;

Float price;

};

Sysntax:- 1.

Struct structre-tag

{

Datatype1 element1;

Datatype2 element2;

Datatype3 element3;

-------------- ------------

Datatype n element n;

};

Main()

{

Structre-tag v1,v2.vn; / / list of variables of stucture tag.

Local variable declaration;

Executable statements;

}

2.

struct structre-tag

{

datatype1 element1;


51/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




datatype2 element2;

datatype3 element3;

-------------- ------------

datatype n element n;

} v1,v2.vn;

main()

{

executable statements;

}

3.

main()

{

Struct structure-tag

{

datatype1 element1;

datatype2 element2;

datatype3 element3;

-------------- ------------datatype n element n;

}

Struct Structre-tag v1,v2.vn;

}

Ex:- 1.

Struct library

{

Char title[20];

Char author[20];

Int pages;

Float price;

};

main()

{

Struct library book1,book2,book3;

}


52/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




2.

Struct library

{

Char title[20];

Char author[20];

Int pages;

Float price;

} book1,book2,book3;

main()

{

Local variables;Executable statements;

}

3.

Main()

{

Struct library

{

Char title[20];

Char author[20];Int pages;

Float price;

};

Struct library book1,book2,book3;

}

Assigning values to structure variables:-

We are assigning values to the variables using member operator . which is called dot

or period operator. This is creates a relationship between the variablename and structure

elelment of the structure tag.

Ex:-

Struct library

{

Char title[20];

Char author[20];

Int pages;


53/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




Float price;

} book1;

main()

{

printlf(enter the book details);

scanf(%s%s%d%f,&book1.title,&book1.author,&book1.pages,&book1.price);

printf(\n the book title is = %s,book1.title);

printf(\n the book title is = %s,book1.author);

printf(\n the book pages are = %d,book1.pages);

printf(\n the book price is = %f,book1.price);

getch();

}

Strucuter and array:-

Array play very important role with sturcture.Sturcture has two types of view with the

array.

1.Array of Sturcture 2.Array within Sturcture

1. Array of Structure : An array structure 1D &2D are Declared by only changing the structure

variables from fundamental type to an array type with no change in the structure declaration.

For 1D:

Sturct sturct-tag variable name[row size];

For 2D:

Sturct sturct-tag variable name[row size][column size];

For example

Main()

{

Sturct student

{

int student1;

int student2;

int student3;

};

Int I,n,total;

Float av;

Struct student st[20];

Printf( \ n Enter the number of Students:);


54/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




Scanf(%d,&n);

For(i=0, i


55/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




}variable list;

2D ;-

Struct structre-tag

{

data type1 element1;

data type2 element2[row][column];

}

Structure with in structure:

A structure can be embedded within another structure. In other words when a structureis declared and processed with in another structure, then it is called Nesting of structure or

structure within structure.

Sturct tag 1

{

element-1;

--------------------

etruct tag 2

{

element-1;.

element n;

}v1;

element-m; }v2;

EX:-

Struct student

{

int rollno;

char name[20];

char address[30];

int phno;

float fees;

struct exam

{

float tel;

float eng;

float compu;


56/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




float tot;

float avg;

}ex[10];

Char dateofbirth[8];

}st[10];

The inner structure element can be linked with the outer structure variable by using the structure

dot operator. This can be represented as:

st[i].ex[j].tel;

Structure and Function:-Structure can be implemented with the function easily. For this process, passing of

arguments takes place similar to the array and variable. This relationship of structure with the

function can be viewed from three angle as;

i) Passing structure to a functionii) Function returning structureiii) Passing array of structure to function.

1.Passing structure to a function:-Similar to passing of array or variable, structure can be passed to the function as

argument.

Syn:-

type specifier function-name (structure-variable); // as actual arguments

type specifier function-name (structure variable) // as formal arguments

struct tagname structurevariable;

{

------

------ }

main()

{

Struct tagname

{

datatype1 ele1;

--------------------


57/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




datatype-n ele n;

}v1;

----------------------

----------------------

function name(v1);

-------------------

getch();

}

Type function name(v2)

Struct tag-name v2;

{

-------------

}

2.Function Returning Structure:

All the values can be computed in the function programs and return a combined value of

whole structure back. This can be explained with a simple problem to compute the net pay of an

employee having structure as:

Main()

{

Sturct employee

{

char name [20];

float bp;

float da;

float hra;

float netpay;

}emp;

Sturct emp npay(emp y);

Printf(\n ENTER THE NAME, BASIC PAY,DA,HRA:);

Scanf(\n%s%f%f%f, emp.name, &emp.bp, &emp.ba, &emp.hra);

Y = npay(y);

Printf(\n Net pay is :%f,y);


58/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




Getche();

}

emp npay(emp Z)

{

Z =Z.bp +Z.hra;

Return(Z);

}

3.Passing array of Structure to function :

A complete complicated passing of an array of structure to the function is a difficult job,but the passing of array becomes very easy by using the passing of array as an individual

element. For example, to compute the average marks of every student (there are five students in

the class ), each having three subjects can be done by using the C program as below:

Main()

{

Res m[100];

int n,I;

printf(\n How many students in the class:);

scanf(\n %d,&n);

printf(\n Enter the data:);

for( i=0; i < n; i++)

{

M[i] =input (m,n);

}

Display(m,n);

getch();

}

res input (res m[],int i)

{

int j;

float tm =0;

printf (\n Enter Rollno andf marks :);

scanf(\n %d, &m*i.rn);

for (j =0;j


59/127



----------------------------------------------------------------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------------------------------------------------------




Scanf(\n%d%c,&m*i.sub*j);

Tm =tm +m[i].sub[j];

}

M[i].av =tm/3;

J =0;

Return m[i];

}

Void display (res m[],int n)

{

int

c entire notes

Documents