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

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

typedef union {
    uint16_t val;
    struct {
        unsigned char mode : 3;
        unsigned char speed : 5;
        unsigned char reserved : 2;
        unsigned char status : 6;
    } fields;
} Register;

uint16_t pack_register(uint8_t mode, uint8_t speed, uint8_t status) {
    // Your logic here
    Register reg;

    reg.fields = {mode, speed, 0, status};

    return reg.val;
}

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;
}