Detect Underflow in Unsigned Subtraction

Code

#include <stdio.h>
#include <stdint.h>

void subtract_with_underflow(uint8_t a, uint8_t b, uint8_t *diff, uint8_t *carry) {
    *diff = a - b;

    if (b > a) {
        *carry = 1;
        *diff = 256 - (b-a);
    } else {
        *carry = 0;
        *diff = a - b;   
    }
}

int main() {
    uint8_t a, b, diff, carry;
    scanf("%hhu %hhu", &a, &b);
    subtract_with_underflow(a, b, &diff, &carry);
    printf("diff = %u, carry = %u", diff, carry);
    return 0;
}

Solving Approach