Code

 Header...
//
// Permute a string from p to the end and print out each
// permutation starting from string start (which never changes)
// Does not avoid duplicates
//
 void permute(char *string_start,char *p){
   ... 

»  char *swap;
  
»  if (p1==0) {// End of string - just print it
»    printf("%s\n", string_start);
»    return ;
  }

// permute the string one shorter than this
»  permute(string_start, p+1);
  
  // Go along the string, swapping each element in turn with p
»  for (swap=p+1; *swap; ++swap) {
»    char tmp=*swap;
    
»    *swap=*p;// swap
»    *p=tmp;
»    permute(string_start, p+1);
»    *p=*swap;// swap back
»    *swap=tmp;
  }
}

 int main(int argc,char * *argv){
   ... 

»  char string[8];

»  while (1) {
»    printf("String to permute?\n");
»    if (scanf("%7s", string)<1) 
      break;
»    printf("Permutations of %s:\n", string);
»    permute(string, string);
  }

»  return 0;
}