Passing pointer to a function (or) pointer and functions

Passing pointer to a function (or) pointer and functions

Case1: pointers are often passed to a function as arguments call be reference mechanism.

/* EXAMPLE PROGRAM FOR CALL BY ADDRESS (or) CALL BY REFERENCE */

#include<stdio.h>

#include<conio.h>

void swap(int *,int *);

main()

{

            int x,y;

            clrscr();

            printf(“\n Enter Two Values =”);

scanf(“%d%d’,&x,&y);

            printf("\nBefore swapping the values are: ");

            printf("\nx :%d, y :%d",x,y);

            swap(&x,&y);

            printf("\n After swapping the values are: ");

            printf("\n x :%d, y:%d",x,y);

}

void swap(int *p, int *q)

{

            int temp;

            temp=*p;

            *p=*q;

            *q=temp;

}

Case2: ‘C’ allows a pointer can store the address of a function.

Syn:  returntype(*pv)( );

We can call the function by using pointer variable.

Example program:

#include<stdio.h>

#include<conio.h>

int show(void);

main()

{

Int (*p)();

P=show;

(*p)();

Printf(“%u”,show);

}

int show()

{

printf(“address of show is: “);

}

Case 3: pointers can be passed as an argument from one function to another function. (or) ‘C’ allows a pointer to pass one function to another function as an argument.

Syntax:    returntype   function_name (pointer to function  (other arguments));

Example program:

int add(int,int);

int process(int (*) (int,int));

main()

{

int x;

clrscr();

x=process(add);

printf(“sum of  numbers %d”,x);

}

int process(int (*p) (int a,int b))

{

int c,a=20,b=10;

c=(*p)(a,b);

return c;

}

int add(int a, int b)

{

return  a+b;

}