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

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

#define MODE_MASK 0x7
#define MODE_POS 0
#define SPEED_MASK 0x1F
#define SPEED_POS 3
#define STATUS_MASK 0x3f
#define STATUS_POS 10

#define MODE(reg, mode) (reg |= (mode & MODE_MASK << MODE_POS))
#define SPEED(reg, speed) (reg |= (speed & SPEED_MASK << SPEED_POS))
#define STATUS(reg, status) (reg |= (status & STATUS_MASK << STATUS_POS)) 
uint16_t pack_register(uint8_t mode, uint8_t speed, uint8_t status) {
    // Your logic here
    uint16_t reg;
    MODE(reg, mode);
    SPEED(reg, speed);
    STATUS(reg, status);
    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;
}