POINTERS AND FUNCTIONS:

POINTERS AND FUNCTIONS:

Every variable in ’C’ has an address except register variable. We can access these addresses using pointers. Likewise, functions in ‘C’ also have addresses. The address of a function can be known by pointers to function.

A pointer to a function can be declared as follows.

            Data type (*function name)(parameter list);

Eg:-

            int (*p)( );

            It indicates ‘p’ is a pointer to a function which stores address of a function.

Ø  A Program to call a function using pointers.

#include<stdio.h>

#include<conio.h>

void (*p)( );

void show( );

void main( )

{

p=show;

           (*p)( );

       }

       void show

       {

printf(“address of function%u”,show);

        }

Functions returning pointers:

                        The way in which a function can return an integer, float or any other datatype, it can also return a pointer, it has to be mentioned explicitly.

            A function returning a pointer can be declared as follows:-

                                    Data type *function name(parameters);

Eg:-

            int *fun();

            void main()

{

            int *p;

            p=fun();

printf(“%u”,p);

}

int *fun()

{

int a=5;

printf(“address of a is”);

return(&a);

}

Here, the declaration int *fun(): indicates that fun() is a function without parameters but return an integer pointer.

Functions returning multiple values:-

            Normally a function can return only one value at a time. But it is possible to make a function return multiple values at a time by using pointers.

Eg:-

#include<stdio.h>

 #include<conio.h>

int fun(int *, int *, int *, int *);

void main()

{

int x,y, sum, diff;

clrscr();

printf(“\n enter any 2 values”);

scanf(“%d%d”,&x,&y);

fun(&x, &y, &sum, &diff);

printf(“sum=%d”,sum);

printf(“diff=%d”,diff);

}

int fun(int *a, int *b, int *c, int *d);

{

            *c=*a+*b;

            *d=*a-*b;

}