18. Set Multiple Bits in 8-bit Register

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

uint8_t set_range(uint8_t reg, uint8_t start, uint8_t end)
{
    uint8_t num = end - start + 1;
    uint8_t mask = (1 << num) - 1;
    return reg | (mask << start);
}

int main()
{
    uint8_t reg, start, end;
    scanf("%hhu %hhu %hhu", &reg, &start, &end);
    printf("%u", set_range(reg, start, end));
    return 0;
}