#include "stdio.h"#include "string.h"char *str(char d[],char s[]){    char *p=d;;    while(*p!='\0')p++;    do    {        *p++=*s++;    }while(*s!='\0');        *p=0;    return d;}int main(){char d[20],s[20];strcpy(d,"string ");strcpy(s,"cat");printf("%s\n",str(d,s));}