#include<stdio.h>
char upperCase(char c);
char lowerCase(char c);

int main()
{

   char upperChar, lowerChar;

   do
   {
        printf ("\n*** uppercase to lowercase conversion ***: ");
        printf ("\nPlease enter an uppercase character: ");
        scanf (" %c", &upperChar);
   }while ((upperChar < 65 || upperChar > 90) && printf ("\nThat is not an uppercase letter!\n"));

   printf ("\nThe character you entered in lowercase: %c\n", lowerCase(upperChar));

   do
   {
        printf ("\n*** lowercase to uppercase conversion ***: ");
        printf ("\nPlease enter a lowercase character: ");
        scanf (" %c", &lowerChar);
   }while ((lowerChar < 97 || lowerChar > 122) && printf ("\nThat is not a lowercase letter!\n"));

   printf ("\nThe character you entered in uppercase: %c\n", upperCase(lowerChar));



}

char upperCase(char c)
{
   return c - 32;
}
char lowerCase(char c)
{
   return c + 32;
}