17. Extract the Nibble from an 8-bit Register

#include <stdio.h>
#include <stdint.h>
unsigned char extractNibble(unsigned char reg, int pos) {
    uint8_t a = 255;
    reg &= ~(a<<4);
    return reg;
}

int main() {
    unsigned char reg;
    int pos;
    scanf("%hhu %d", &reg, &pos);
    printf("%d", extractNibble(reg, pos));
    return 0;
}