#include

int strlen( char *s )

{

int slen , i ;

i = 0 ;

while( s[i] )

i ++ ;

slen = i ;

return slen ;

}

int strcat(char *s , char *t)

{

int slen , tlen , i , j ;

slen = strlen( s ) ;

tlen = strlen( t ) ;

for( i = slen , j = 0 ; j

{

s[i+j] = t[j] ;

}

s[i+j] = "\0" ;

return 0 ;

}

int main( )

{

char str1[15] = "abcdefg" , str2[15] = "hijklmn" ;

printf( "%s %s\n" , str1 , str2 ) ;

strcat( str1 , str2 ) ;

printf( "%s %s\n" , str1 , str2 ) ;

return 0 ;

}