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

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

#define MODE_MASK      0x7U  // 3 bits
#define SPEED_MASK     0x1FU // 5 bits  
#define RESERVED_MASK  0x3U  // 2 bits (referential use)
#define STATUS_MASK    0x3FU // 6 bits

#define MODE_SHIFT     0U
#define SPEED_SHIFT    3U
#define RESERVED_SHIFT 8U
#define STATUS_SHIFT   10U

uint16_t pack_register(uint8_t mode, uint8_t speed, uint8_t status) {
    // Your logic here
    uint16_t pack_value = 0U;
    // We truncate the input using an & to ensure it doesn't exceed its size.
    pack_value |= ((uint16_t)(mode & MODE_MASK) << MODE_SHIFT);
    pack_value |= ((uint16_t)(speed &SPEED_MASK) << SPEED_SHIFT);
    pack_value |= ((uint16_t)(status & STATUS_MASK) << STATUS_SHIFT);

    return pack_value;
    
}

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;
}