Thread: help with function

Hello guys,
I would like to ask you if anybody knows how to fix or upgrade my function "set". My teacher wrote me that I have to allocate the function inside not in main. And second thing is how to change that the pointers to pointers in function would be simplified.
Thanks for help

Code:

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

#define BUFFER_SIZE 128

int set(char *in, char **out);

int main(int argc, char **argv)
{
  char inStr[BUFFER_SIZE] = { 0 };
  char *outStr = NULL;
  int changed = 0;
  printf("Exercise 10.1\n");

  printf("Enter string:");
  if (!fgets(inStr, BUFFER_SIZE, stdin)) {  //enter string

    printf("Error load string...\n");
    exit(EXIT_FAILURE);
  }
  int lenght = strlen(inStr);   //include '\n' char as last
  inStr[lenght - 1] = '\0';     //remove last char '\n' from fgets function
  outStr = (char *) malloc(lenght); //alloc new string of lenght
  if (!outStr) {
    printf("Error in alloc memory...\n");
    exit(EXIT_FAILURE);
  }
  changed = set(inStr, &outStr);  //call function
  printf("Original string: %s\n", inStr);
  printf("Changed string: %s and changed letters: %d\n", outStr, changed);
  free(outStr);                 //free alloc memory
  getchar();
  return 0;
}

int set(char *in, char **out)
{
  char *tmpString = *out;       //temp variable, out cannot be used like out++
  int changed = 0;              //changed letters
  while (*in) {
    if (*in >= 65 && *in <= 90) {
      *tmpString = *in + 32;
      changed++;
    } else if (*in >= 97 && *in <= 122) {
      *tmpString = *in - 32;
      changed++;
    } else {
      *tmpString = *in;
    }
    in++;
    tmpString++;
  }
  *tmpString = '\0';            //add ending char '\0'
  return changed;
}