Question

using C:

Write code for a function with the following prototype:

/*
 * Mask with least signficant n bits set to 1
 * Examples: n = 6 --> 0x3F, n = 17 --> 0x1FFFF
 * Assume 1 <= n <= w
 */
int lower_one_mask(int n);

Your function should follow the bit-level integer coding rules. Be careful of the case n =w.

Answer 1

Program

#include <stdio.h>

int lower_one_mask(int n)
{
int bits_mask = (n == sizeof(int) << 3) - 1;
int m = ~(bits_mask << n);
return m;
}

int main(int argc, char **argv)
{
printf("n=6 ---> 0X%X\n", lower_one_mask(6));
printf("n=17 ---> 0X%X\n", lower_one_mask(17));
printf("n=32 ---> 0X%X\n", lower_one_mask(32));
}

Output