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) {
    uint8_t n = end - start + 1;       // set width of bit fild
    uint8_t base = ~(0b11111111 << n); // setup register with correct bit field a.k.a 0x000000111 
    uint8_t mask = base << start;      // set desired mask
    return reg | mask;
}

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