27. Extract Bit Field from 16-bit Register

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

uint8_t extract_field(uint16_t reg) 
{
    int num=0;
    for(int i=4,j=0;i<=8;i++,j++)
    {
        if((reg>>i)&1==1)
            num|=(1<<j);
        else
            num&=~(1<<j);
    }
    return num;
}

int main() {
    uint16_t reg;
    scanf("%hx", &reg);
    printf("%u", extract_field(reg));
    return 0;
}