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

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

#define SET_MODE(reg,x) (reg|=((x & 0x07)<<0))
#define SET_SPEED(reg,x) (reg|=((x & 0x1F)<<3))
#define SET_STATUS(reg,x) (reg|=((x & 0x3F)<<10))

uint16_t pack_register(uint8_t mode, uint8_t speed, uint8_t status) {
    uint16_t reg;
    SET_MODE(reg,mode);
    SET_SPEED(reg,speed);
    SET_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;
}