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

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

#define MODE_MASK (((1u<<3)-1))
#define SPEED_MASK (((1u<<5)-1))
#define RESERVED_MASK (((1u<<2)-1))
#define STATUS_MASK (((1u<<6)-1))

uint16_t pack_register(uint8_t mode, uint8_t speed, uint8_t status) {
    uint16_t packed_reg = 0;
    packed_reg |= (mode & MODE_MASK);
    packed_reg |= ((speed & SPEED_MASK)<<3);
    packed_reg |= ((status & STATUS_MASK)<<10);
    
    return packed_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;
}