23. Set Baud Rate Field in Control Register

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

uint32_t set_baud_rate(uint32_t reg, uint8_t baud) {
    const uint8_t pos = 8;
    const uint8_t field = 4;

    uint32_t mask = ~(0xFFFFFFFF << field); // set width of mask according to field
    reg &= ~(mask << pos);                  // apply inverted mask to clear target bit in register
    uint32_t ext_baud = baud << pos;        // coerce baud to 32-bet and shift on positon; 
    reg |= ext_baud;                        // sum up shifted val and cleared register
    return reg;
}

int main() {
    uint32_t reg;
    uint8_t baud;
    scanf("%u %hhu", &reg, &baud);
    printf("%u", set_baud_rate(reg, baud));
    return 0;
}