Consider an unsigned integer in which rightmost bit is numbered as zero. Write a function checkbits(x, p, n) which returns true if all "n" bits starting from position "p" are turned on. For example, checkbits(x, 4, 3) will return true if bits 4, 3 and 2 are 1 in number x.

#include<stdio.h>
#include<conio.h>
#include<Windows.h>
#include<math.h>

#define _BV(x) 1<<x

int checkbits(int, int, int);

int main()
{
	int status;
	status = checkbits(14, 3, 3);
	if (status)
		printf("Required bits are ON\n");
	else
		printf("Required bits are OFF\n");
	_getch();
	return 0;
}

int checkbits(int x, int p, int n)
{
	unsigned int andmask = 0;
	int i, j;
	for (i = 0, j = p; i < n; i++, j--)
		andmask |= _BV(j);
	if ((x & andmask) == andmask)
		return 1;
	else
		return 0;
}