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

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

#define MODE_FIELD(r,b)     (r |= (b & 0x07) << 0)
#define SPEED_FIELD(r,b)    (r |= (b & 0x1F) << 3) 
#define STATUS_FIELD(r,b)   (r |= (b & 0x3F) << 10) 
uint16_t pack_register(uint8_t mode, uint8_t speed, uint8_t status) {
    uint16_t reg =0;
    MODE_FIELD(reg,mode);
    SPEED_FIELD(reg, speed);
    STATUS_FIELD(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;
}