Extract the Nibble from an 8-bit Register

Code

#include <stdio.h>

unsigned char extractNibble(unsigned char reg, int pos) {
    unsigned char a = 0xF0; //extracting lower nibble
    unsigned char b = 0x0F; //extracting upper nibble
    if( pos ){
        return ( ( reg & a )>>4 );
        }
    else{
        return ( reg & b );
        }
}

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

Solving Approach