19. Extract a Bit Field from a 32-bit Register

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

uint32_t extract_field(uint32_t reg, uint8_t pos, uint8_t len) {
    // Your code here
    uint8_t i;
    uint32_t mask=0;
    for (i=pos; i < (pos + len); i++)
    {
        mask = mask | (1 << i);
    }
    reg = (reg & mask) >> pos;
    return reg;
}

int main() {
    uint32_t reg;
    uint8_t pos, len;
    scanf("%u %hhu %hhu", &reg, &pos, &len);
    printf("%u", extract_field(reg, pos, len));
    return 0;
}

create a mask of 1s from the first bit to the last

bitwise AND the mask with the register 

right shift the result to the beginning of the register