Bitwise AND and Bitwise OR Operations Results

Binary numbers,

Any number bitwise ANDed with N ones results in itself; or ORed with N zeros results in itself.

Any number bitwise ANDed with N zeros results in N zeros; any number bitwise ORed with N ones results in N ones.

Bitwise ANDing with N ones.

1 0 1 0 1 1 0 1 1 1 1
1 1 1 1 1 1 1 1 1 1 1
1 0 1 0 1 1 0 1 1 1 1

This property can be used to obtain certain bits of a number.

Obtain digits at certain positions

For example, to get the bits from positions 8 to 11 of an int type.
C# version

            int num, mark;          
            Console.WriteLine("输入一个整数(大于256)");
            num = Convert.ToInt32(Console.ReadLine());
            num = num >> 8;
            mark = ~(~0 << 4);    // Construct 00000000 00000000 00000000 00001111
			// mark = 0b00000000_00000000_00000000_00001111;
            num = num & mark;
            Console.WriteLine(num);
            Console.ReadKey();

C version

#include <stdio.h>
int main()
{
	printf("输入数字(256以上)");
	int	num;
	int	mark;
	scanf("%d", &num);
	num	= num >> 8; /* Shift right by 8 bits to make bits 8-11 into bits 0-4 */
	mark	= num & ~(0 << 4);
	printf("result = 0x%x", mark);
	return(0);
}

Output a number's binary

The principle is that 0 or 1 bitwise ANDed with 1 equals itself, and bitwise ANDed with 0 equals 0.

Given any positive integer input, output the binary form of that number.
C version

#include <stdio.h>
int main()
{
	printf("输入数字(256以上)");
	int	num;
	int	mark;
	printf("%d", '1');
	scanf("%d", &num);
	mark = 1 << 31;

	int i = 0;
	for (i = 0; i <= 31; i++)
	{
		printf("%c", num & mark ? '1' : '0'); /* The result must either be greater than 0 or equal to 0 */
		/* putchar(num & mark ? '1' : '0'); /* Force conversion to 8-bit variable (lower 8 bits) */ */
		num = num << 1;
		if ((i + 1) % 8 == 0)
			putchar(',');
	}
	putwchar('B');
	return(0);
}

C# version

            uint num;
            int mark;
            Console.WriteLine("输入一个整数(大于256)");
            num = Convert.ToUInt32(Console.ReadLine());
            mark = 1 << 31;
            string str = string.Empty;

            for (int i = 0; i < 31; i++)
            {
                Console.Write((num & mark) == 0 ? '0' : '1'); // The result at each step should either be 1 or 0,
                                                              // the result must either be greater than 0 or equal to 0
                num = num << 1;
                if ((i + 1) % 8 == 0)
                    Console.Write(',');
            }
            Console.Write("B");
            Console.ReadKey();