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 ctrl;

    ctrl.bits.enable = e;
    ctrl.bits.mode = m;
    ctrl.bits.interrupt = i;
    ctrl.bits.reserved = 0;

    ctrl.reg = ctrl.bits.enable | (ctrl.bits.mode << 1) | (ctrl.bits.interrupt << 3) |
        (ctrl.bits.reserved << 4);
    printf("%d", ctrl.reg);

    return 0;
}

Solving Approach