Pack Multiple Fields into a 16-bit Control Register

Code

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

// Define shifts
#define MODE_SHIFT     0
#define SPEED_SHIFT    3
#define RESERVED_SHIFT 8
#define STATUS_SHIFT   10

// Create a Masks
#define MODE_MASK       (0x07 << MODE_SHIFT)
#define SPEED_MASK      (0x1F << SPEED_SHIFT)
#define RESERVED_MASK   (0x03 << RESERVED_SHIFT)
#define STATUS_MASK     (0x3F << STATUS_SHIFT)

uint16_t REG = 0;
uint16_t pack_register(uint8_t mode, uint8_t speed, uint8_t status) {
    REG |= ((mode   << MODE_SHIFT)    & MODE_MASK);
    REG |= ((speed  << SPEED_SHIFT)   & SPEED_MASK);
    REG |= ((status << STATUS_SHIFT)  & STATUS_MASK);
    REG |= ((0x00   << RESERVED_SHIFT) & RESERVED_MASK);
    return REG;
}

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;
}

Solving Approach