rot13

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

char encode (char letter);
int main (int argc, char* argv []) {
   char letter;
   printf ("Enter a letter\n");
   scanf ("%c", &letter);
   char encode (char letter);
   printf ("%c\n", letter);

   return EXIT_SUCCESS;
}
char encode (char letter) {
   int encodedLetter;
   if ((letter >= 'a') && (letter <= 'm')) {
      encodedLetter = (letter + 13);
   } else if ((letter >= 'n') && (letter <= 'z')) {
      encodedLetter = (letter - 13);
   } else if ((letter <= 'a') && (letter >= 'z')) {
      encodedLetter = letter;
   }
   return encodedLetter;
}