How to reverse a String without using C functions

clipped from www.allinterview.com How to reverse a String without using C functions ? the above is slightly wrong this is the corrected one.. char * rev_string (char * str) { char temp; int i , j; for (i = 0 ; str[i]!= '\0' ; i++); for(j = 0 ; j < i ; j++ , i--) { temp = str[j]; str[j] = str[i]; str[i] = temp; } return str; } #include<stdio.h> void reverse(char *); void main() { char str[]="Hello"; reverse(str); printf("Reverse String is %s",str); } void reverse(char *p) { char *q=p; while(*++q!='\0'); q--; while(p<q) { *p=*p+*q; *q=*p-*q; *p=*p-*q; p++; q--; } }