80. Register Bitfields Using Struct Overlay

#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 regis;
    regis.reg = 0x00;

    regis.bits.enable    = e;
    regis.bits.mode      = m;
    regis.bits.interrupt = i;

    printf("%d", regis.reg);

    return 0;
}