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

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

#define MODE_MASK  0x07
#define SPEED_MASK 0x1F
#define STATUS_MASK 0x3F

#define MODE(mode) (mode & MODE_MASK)
#define SPEED(speed) ((speed & SPEED_MASK) << 3)
#define STATUS(status) ((status & STATUS_MASK) << 10)
uint16_t pack_register(uint8_t mode, uint8_t speed, uint8_t status) {

    return uint16_t(MODE(mode) | SPEED(speed) | STATUS(status));    
}

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;
}