Set Multiple Bits in 8-bit Register

Code

#include<stdio.h>
int main()
{
    int reg , pos, start , end ;
    scanf("%d %d %d ",&reg,&start,&end);
    while(start <= end)
    {   
        int pos=start;
        reg |=(1<<pos);
        start++;
    }
    printf("%d",reg);
    return 0;
}

Solving Approach