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

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

#define SET_MODE(val) ((uint16_t)((val & 0b111) << 0))
#define SET_SPEED(val) ((uint16_t)((val & 0b11111) << 3))
#define RESERVED (~(3 << 8))
#define SET_STATUS(val) ((uint16_t)((val & 0b111111) << 10))

uint16_t pack_register(uint8_t mode, uint8_t speed, uint8_t status) {
    uint16_t pack = 0;
    pack |= SET_MODE(mode);
    pack |= SET_SPEED(speed);
    pack &= RESERVED;
    pack |= SET_STATUS(status);
    return pack;
}

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;
}