Extract the Nibble from an 8-bit Register

Code

#include <stdio.h>

#define LOW_NIBBLE 0
#define UPPER_NIBBLE 1


unsigned char extractNibble(unsigned char reg, int pos) {
    char selected_nibble;

    switch(pos) {
        case LOW_NIBBLE:
            /* Take the four lower nibble (lower bits) 00001111 */
            selected_nibble = reg & 0x0F;
            break;
        case UPPER_NIBBLE:
            /* Take the four upper nibble */
            reg = (reg >> 4); // Right shift the four upper bits at the low nibble pos.
            selected_nibble = reg & 0x0F; // Collect the upper nibble.
            break;
        default:
            printf("Invalid nibble pos");
            break;
    }
    return selected_nibble;
}

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

Solving Approach