/* * Concatenate s2 on the end of s1.  S1's space must be large enough. * Return s1. */char *strcat(s1, s2)register char *s1, *s2;{	register char *os1;	os1 = s1;	while (*s1++)		;	--s1;	while (*s1++ = *s2++)		;	return(os1);}