Bitwise Operations: AND, OR, XOR, NOT

Bitwise operations work on individual bits of binary numbers. They are fundamental to low-level programming, cryptography, graphics, and performance optimization.

The four basic bitwise operations:

AND (&) — Both bits must be 1:

  1010 & 1100 = 1000

Use case: Masking specific bits. To extract the lower 4 bits of a byte, AND with 0x0F.

OR (|) — At least one bit must be 1:

  1010 | 1100 = 1110

Use case: Setting flags. To enable bit 3, OR with 0x08.

XOR (^) — Exactly one bit must be 1:

  1010 ^ 1100 = 0110

Use case: Toggling bits, simple encryption, swapping values without a temporary variable.

NOT (~) — Inverts every bit:

  ~1010 = 0101

Use case: Creating inverse masks, two's complement negation.

Practical applications:

• Feature flags: Combine permissions using OR: READ | WRITE = 0b110. Check with AND: flags & READ !== 0.
• IP subnetting: AND an IP with a subnet mask to get the network address.
• Color manipulation: Extract the green channel from #4169E1: (0x4169E1 >> 8) & 0xFF = 0x69 = 105.
• Hash functions: XOR is used extensively in hash algorithms because it distributes bits evenly.
• Cryptography: XOR is the foundation of stream ciphers and one-time pads: plaintext ^ key = ciphertext, and ciphertext ^ key = plaintext.

Common bit tricks:

• Check if a number is even: n & 1 === 0
• Check if a number is a power of 2: n & (n - 1) === 0
• Clear the lowest set bit: n & (n - 1)
• Isolate the lowest set bit: n & (-n)

Mastering bitwise operations makes you more effective at systems programming, competitive coding, and understanding how hardware processes data.