C program strcat string

string add using  strcat in c program : 

In the C Programming Language, the strcat function appends a copy of the string pointed to by s2 to the end of the string pointed to by s1. It returns a pointer to s1 where the resulting concatenated string resides.

Example : 

Input : 

    str:  atikur 

    str2:  rtahman 

Output : atikur rahman

program code : 

#include<stdio.h>

#include<string.h>

int main()

{

    char str[100]="atikur ";

    char str2[100]="rahman";

    strcat(str, str2);

    printf(" %s ",str);

    return 0;

}

Output :

without (strcat) string function in program : 

Example : 

Input : 

    str:  atikur 

    str2:  rtahman 

Output : atikur rahman

program code : 

#include<stdio.h>

int main()

{

    int i,j;

    char st[100]="atkur ";

    char st2[100]="rahman";

    for(i=0;st[i]!='\0'; i++);

    for(j=0;st2[j]!='\0'; j++)

    {

        st[i+j]=st2[j];

    }

    printf("%s",st);

    return 0;

}

output :