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 |= (mode & 0x7) << 0;       // bits 0-2
    reg |= (speed & 0x1F) << 3;     // bits 3-7

    // bits 8-9 reserved = 0

    reg |= (status & 0x3F) << 10;   // bits 10-15

    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\n", reg);

    return 0;
}