A pointer is always declared as same type of a variable type. So that pointer can hold the address of that type variable. For example,

int *ptr;

int num = 25;

ptr = #

In the above example, ptr is declared as pointer variable, which can point a memory block of type integer variable. In this example, num is declared as integer and its address (&num) is assigned to the pointer variable. Like this we can use two pointer variables to hold the address of two variables to interchange the values of two variables. The required code is as follows:

#include<stdio.h>

void swap(int *ptr1, int *ptr2){

int temp = *ptr1;

*ptr1 = *ptr2;

*ptr2 = temp;

}

int main(){

int num1;

int num2;

printf("Enter two values::");

scanf("%d %d",&num1,&num2);

printf("Values before swapping....\n");

printf("num1 = %d, num2 = %d\n",num1, num2);

swap(&num1, &num2);

printf("Values after swapping.....\n");

printf("num1 = %d, num2 = %d",num1,num2);

return 0;

}