Concate

#include <stdio.h>
int main()
{
    char s1[100], s2[100], i, j;
    printf("Enter first string: ");
    scanf("%s",s1);
    printf("Enter second string: ");
    scanf("%s",s2);
    for(i=0; s1[i]!='\0'; ++i);  /* i contains length of string s1. */
    for(j=0; s2[j]!='\0'; ++j, ++i)
    {
        s1[i]=s2[j];
    }
    s1[i]='\0';
    printf("After concatenation: %s",s1);
    return 0;
}