swap_by_reference.c

#include <stdio.h>

void swap(int *, int *); // The right way is to declare function prototype in header.

int main()
{
    int a, b;

    // printf("Enter the value of a:\n");
    // scanf("%d", &a);
    // printf("Enter the value of b:\n");
    // scanf("%d", &a);

    a = 10;
    b = 20;

    printf("[I] Before Swapping\n");
    printf("==> a = %d\n", a);
    printf("==> b = %d\n", b);

    swap(&a, &b);

    printf("\n[I] After Swapping\n");
    printf("==> a = %d\n", a);
    printf("==> b = %d\n", b);

    return 0;
}

void swap(int *a, int *b)
{
    int temp = *a;
    *a = *b;
    *b = temp;
}