Bitwise Operators

Bitwise Operators

Bitwise operators work on individual bits of integer values. They are essential for low-level programming, flags, and performance-critical code.

The Operators

The Borg think in binary. "You will be assimilated" -- one bit at a time.

How It Works

Think in binary:

  5 = 0101
  3 = 0011
---------
  & = 0001 (1)   -- both bits must be 1
  | = 0111 (7)   -- either bit can be 1
  ^ = 0110 (6)   -- exactly one bit must be 1

Bit Flags

A common pattern is using individual bits as boolean flags:

#define READ    1   // 001
#define WRITE   2   // 010
#define EXEC    4   // 100

int perms = READ | WRITE;  // 011 = 3
if (perms & READ) {
    printf("Can read\n");
}

Setting, Clearing, and Toggling Bits

int flags = 0;
flags = flags | (1 << 2);   // set bit 2
flags = flags & ~(1 << 2);  // clear bit 2
flags = flags ^ (1 << 2);   // toggle bit 2

Left Shift as Multiply

Shifting left by n is the same as multiplying by 2^n:

int x = 3 << 2;  // 3 * 4 = 12

Your Task

Write a function int count_set_bits(int n) that counts how many bits are set to 1 in the binary representation of n. Use bitwise AND and left shift to check each bit position. Print the result for 0, 7, 255, and 1.