18. Set Multiple Bits in 8-bit Register

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

uint8_t set_range(uint8_t reg, uint8_t start, uint8_t end) {
    // Ensure start <= end
    if (start > end || end > 7) return reg;

    // Create mask for bits from start to end
    uint8_t mask = ((1 << (end - start + 1)) - 1) << start;

    // Set bits in that range
    reg |= mask;

    return reg;
}

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