C program to swap two strings, i.e., their contents are interchanged

#include <stdio.h>
#include <string.h>

int main()
{
  char first[100], second[100], t[100];

  printf("Enter first string\n");
  gets(first);

  printf("Enter second string\n");
  gets(second);

  printf("\nBefore Swapping\n");
  printf("First string: %s\n", first);
  printf("Second string: %s\n\n", second);

  strcpy(t, first);
  strcpy(first, second);
  strcpy(second, t);

  printf("After Swapping\n");
  printf("First string: %s\n", first);
  printf("Second string: %s\n", second);

  return 0;
}

output:

Before Swapping:

hello

First string:

bye

Second string:   hello

After Swapping  bye

First string: bye

Second string: hello