01  #include <stdio.h>
02  #include <string.h>
03  
04  int main()
05  
06  {
07   char s1[80];
08   char s2[80];
09  
10   printf("Enter the first string :");
11   gets(s1);
12   printf("Enter the second string :");
13   gets(s2);
14   strcat(s1,s2);
15   puts(s1);
16   
17   return 0;
18  }

 OUTPUT :
 
 Enter the first string :Hello
 
 Enter the second string :World
 
 HelloWorld