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 cr = {0}; // khởi tạo 0
    cr.bits.enable    = e & 0x01; // đảm bảo 1 bit
    cr.bits.mode      = m & 0x03; // đảm bảo 2 bit
    cr.bits.interrupt = i & 0x01;

    printf("%u\n", cr.reg);

    return 0;
}

Solving Approach