大小写转换

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

int main(void)
{
   char c;

   while ((c = getchar()) != EOF && ((c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z')) ) {
      printf ("%s%c\n", "The uppercase is   :", c & 0xDF);
      printf ("%s%c\n", "The lowercase is   :", c | 0x20);
      getchar();
}
   system("pause");
   return 0;
}