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

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

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

uint16_t pack_register(uint8_t mode, uint8_t speed, uint8_t status) {
    uint16_t reg =0;
    reg |= SET_MODE(mode) | SET_SPEED(speed) | SET_STATUS (status);
    reg &= ~(((1U<<2)-1)<<8);
    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;
}