reverse.c

#include <stdio.h>
#include <string.h>

#define MAXLEN 256

void reverse(char *s, char *r);

main() {
  char s[MAXLEN] = "hello reversed world!";
  char r[MAXLEN];
  reverse(s, r);
  printf("%s\n", r);
}

void reverse(char *s, char *r) {
  int i = strlen(s)-1;
  int j = 0;

  while((r[j++] = s[i--]) != '\0');
}