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

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

uint16_t pack_register(uint8_t mode, uint8_t speed, uint8_t status) 
{
    // Your logic here  
    if (mode > 7) mode = 7;         // 3 bits max
    if (speed > 31) speed = 31;     // 5 bits max
    if (status > 63) status = 63;  

    uint16_t ans = 0;
    ans |= (mode & 0x7) | ((speed & 0x1F) << 3) | ((status & 0x3F) << 10);
    return ans;
}

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;
}