#include <stdio.h>

typedef unsigned char byte;

byte a = 0x41; // A
byte b = 0x61; // a

int main(int argc, char const *argv[])
{
    byte c = b - a;
    printf("The value of a - b is %d\n", c);
    printf("The hex value of c is: 0x%02x\n", c);
    return 0;
}