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) {
    uint16_t reg=0;
    reg&=~(((1U << 2)-1) << 8); //clear reserved bits
    reg|=(((1U << 3)-1) & (mode)) << 0; //sets mode bits
    reg|=(((1U << 5)-1) & (speed)) << 3;
    reg|=(((1U << 6)-1) & (status)) << 10;
    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;
}