Register Bitfields Using Struct Overlay

Code

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

typedef union {
    struct {
        uint8_t enable    : 1;
        uint8_t mode      : 2;
        uint8_t interrupt : 1;
        uint8_t reserved  : 4;
    } bits;
    uint8_t reg;
} ControlRegister;

int main() {
    uint8_t e, m, i;
    scanf("%hhu %hhu %hhu", &e, &m, &i);

    // Construct and print register value
    ControlRegister C;
    uint8_t res = 0;
    C.bits.enable = e;
    C.bits.mode = m;
    C.bits.interrupt = i;
    res |= C.bits.interrupt = i;
    res <<= 2;
    res |= C.bits.mode;
    res <<= 1;
    res |= C.bits.enable;

    printf("%u", res);

    return 0;
}

Solving Approach