Data Structure and CPart-6

Naming a Function

• Any valid variable-name can be given to the user-defined function.

• The main program itself is considered as a function in C.

• Whenever a C program is executed, execution starts from the function.

• So there should be only one main function.

Example of Code Program# include <stdio.h>main( ){

------ Calling

------Function

------}

------}calculation()int…….;{

------ Called

------Function------}

Structure of a Function

The general structure is return type function name (list of parameters)

Syntax:

parameter declaration.{ Statements :}

Body of the Function

• The body of the function contains a variable declaration part, processing and a return statement.

• The variables declared within the body of a function are called ‘local variables’.

• These variables can be used or referred to only within the body of that function and hence the name.

• These variables have no meaning outside the body of that function.

• The body of the function is given within braces.

Example:cube ( int x ){ int cubes; cubes = x*x*x;

return (cubes); }

The Return-Statement

• The calculation part can contain either assignment statement or any valid arithmetic logic expressions.

• If there is a value that has to be returned to the calling function

• The return statement is used.

The general syntax is :return [value];

Example:# include <stdio.h>main( ){

int a ;a = retfun( );printf(“a = %d”,a)getch( );

}

retfun( ){

return(1);}

The output is a = 1

Example of Code Program

Function Declaration

• Any C function by default returns an int value.

• If a function should return a value other than integer.

• then it is necessary to explicitly mention so in the calling function declaration or function prototype.

• The general format is:• data-type function-name (list of

parameters);

# include <stdio.h>main ( ){float x, y ;

float div (float a, float b);

printf (“enter 2 number”);

scanf (“%f%f”,&x,&y);

printf (“The div value is %f” ,div (x,y);

getch ( );}Float div (a,b)Float a,b;{

Return(a/b);}

Void Function Type •If the function returns no value then it is called void function.

•Such function must be declared as a void function.

•In general void is an empty data type.General form •Void function name ( )

Example-1

#include<Stdio.h>#include<Conio.h>void welcome (char name [ ]);{Printf (“ Welcome % s” name);}

Example-2

# include <stdio.h>void fun1 (void);void fun2 (viod);main ( ){

clrscr ( ) ;fun1 ( ) ;getch ( ) ;

}

void fun2(void){

Printf (“C Programming”);}

Parameter in FunctionsA function is called by specifying its name followed by a list of arguments.

When a function is invoked, the formal parameters are initialized to the actual parameters used in the function call operator .

The corresponding arguments in the function Program are called actual parameter.

Declarationmain ( ){

a = area (l,b);}{

area (x,y)

……}

main ( ){

int a,b;result = mul (a,b):

……

} mul(i,j); int i,j;{

…… }

LIBRARY FUNCTIONS

C offers a rich collection of library functions.

Any of these functions can be called from any

C program.

To invoke these functions we have to include

the appropriate header file in the program.

Utility Functions

• Utility Functions is symbol by<stdlib.h>.

• It is an header file.

• Utility Functions has servral types. Following are given below

atof ( )• This is used to convert a string into a floating-point value. • The general format is atof (string);Example:main ( ){

char a [20] = “222.33”;float c;C = atof (a);

} The output will be C = 222.33

atoi ( )This function is used to convert a string into an integer value..The general form is: atoi (string);Example:main ( ){

char a[20] = “2233”;int c;c = atof(a) + 5;

}The output is C= 2238

Mathematical Functions

• Mathematical Functions Symbol <math.h> • It has several types. Following are given

below;-

floor ( )• This function is used to find the floor of a

value x.

• The floor of x is the first smaller integer. The general format is:

• Floor (x);• Example:-• floor (2,9) = 2• floor (-2.1) = 3

ceil ( )

This function returns the round value of the nearest highest integer. The general format is:

ceil (x);Example:ceil(2.6) = 3 ceil(5.2) = 6 ceil(-4.3) = -4

pow ( )

This function is used to find xy. The general format is:

Pow (x,y);Example:pow (2.3);The output is 8.

exp ( )

• This function is used to find the exponential value.

• The general format is:• Exp(x);

String Function

• String Function is symbol <string.h>

• It also using character and words.

• These functions are for string manipulations.

These functions can be classified according to

their performance as follows:-

Joining of two strings

1) strcat 2) strncati.strcat: This function is used to add two strings. The result is stored in the destination string that is the first string. The general form is: strcat(string 1, string 2);

ii. strncat: This function is similar to ‘strcat()’ except. That it binds only n characters of string 2 with string 1. The general form is: strncat(string 1, string 2, n);

Conversion of Strings

1) strlur: This function is used to convert a string containing uppercase to lowercase. The general Format is: strlwr (string);

2) strupr: This function is used to convert a string containing lowercase to uppercase. The general format is: strupr (string);3) strrev: This function is used to reverse the string. The general format is strrev (string);

• 4) strset: This function is used to replace all

the characters in a string with a particular given character.

The general format is: strset(string, char);

where the string will be replaced by the character.

5) strnset: This function is similar to strset ( ). The only difference is that we can specify the number of characters to be replaced in the given string. The general format is: strnset (string, char , n);

Comparison of string

1) strcmp This function is used to compare the

two strings. The function is case sensitive. The general format is:• strcmp (string 1, string2);• Example:• string 1 = “Canada”• string 2 = “Africa”

2) strncmp :

This function will compare just n

characters of string 2 with string 1.

This is case sensitive.

The general format is:

stricmp(string 1, string 2, n);

3) stricmp : This function is similar to strcmp(). It is an except that this is non-case sensitive. The general format is: stricmp(string 1, string 2);

Other String Functions

1) Strlen This function is used to find the

length of the string. This function will not count null-

terminating character. The general format is: strlen(string);

2) strcpy This function is used to copy string 2 to string 1 including the null terminating character of string. The general format is: strcpy (string1, string2); Here string 1 is the destination where the string 2 will be copied. After the execution the old characters in string 1 will be completely erased.

3) Strncpy This function is similar to strcpy(), except that it copies n characters on string 2 to string 1. The general format is: strncpy(string1, string, n);

Character Class Test Functions Character class test functions is symbol by <ctype.h>.

1)isalnum ( ) Tests whether a character is an alphabet or a number. Isalnum(int c);

• 2. islower ( )• Test whether a charcter is a lower case or

not.• Islower (int c);• 3. isupper ( )• Tests whether the charcter is a uppercase.• Isupper(int c);

2. islower ( ) Test whether a character is a lower case or not. Islower (int c);

3. isupper ( ) Tests whether the charcter is a uppercase. Isupper(int c);

4) tolower ( ) This function translates character to lowercase. Tolower(int c);

5. toupper ( ) This function translates character to uppercase. Toupper (int c);