25. Pack Multiple Fields into a 16-bit Control Register

#include <stdio.h>
#include <stdint.h>
typedef union
{
    struct 
    {
        uint32_t mode : 3;
        uint32_t speed : 5;
        uint32_t reserved : 2;
        uint32_t status : 6;
    } Bits;
    uint16_t value;
} Register16;

uint16_t pack_register(uint8_t mode, uint8_t speed, uint8_t status) {
    Register16 reg;

    reg.Bits.mode = mode;
    reg.Bits.speed = speed;
    reg.Bits.status = status;
    return reg.value;
}

int main() {
    uint8_t mode, speed, status;
    scanf("%hhu %hhu %hhu", &mode, &speed, &status);

    uint16_t reg = pack_register(mode, speed, status);
    printf("%u", reg);
    return 0;
}