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

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

#define MODE_POS        0
#define SPEED_POS       3
#define RESERVED_POS    8
#define STATUS_POS      10

#define MODE_LEN        0x07U
#define SPEED_LEN       0x1FU
#define RESERVED_LEN    0x03U
#define STATUS_LEN      0x3FU

uint16_t pack_register(uint8_t mode, uint8_t speed, uint8_t status) {
    // Your logic here
    uint16_t retVal = 0x0000;

    retVal |=  (mode & MODE_LEN)     << MODE_POS;
    retVal |=  (speed & SPEED_LEN)   << SPEED_POS;
    retVal &= ~(RESERVED_LEN         << RESERVED_POS);
    retVal |=  (status & STATUS_LEN) << STATUS_POS;

    return retVal;
}

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;
}