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) {
    // determine mask width
    uint8_t mask = 0x00;
    for(int i = 0; i < (end-start+1); i++) {
         mask += (1 << i);
    }
  
    // shift start times
    mask = (mask << start);

    
    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;
}