C Bitwise Operators

Bitwise operators work on the tiny 0s and 1s inside numbers, like flipping rows of light switches. They let you check or change individual switches.

In this page:

Bitwise AND (&)
Bitwise OR (|)
Bitwise XOR (^)
Bitwise NOT ()
Shift Operators (<< and >>)

Syntax

result = value1 & value2;  // AND
result = value1 | value2;  // OR
result = value1 ^ value2;  // XOR
result = ~value;           // NOT
result = value << n;       // shift left
result = value >> n;       // shift right

Bitwise AND (&)

& compares two numbers bit by bit and produces a 1 in each position where both operands have a 1, and a 0 everywhere else -- often used to check or isolate specific bits within a value, like reading configuration flags.

Example: Bitwise AND (&)

// Include standard input/output (printf, scanf)
#include <stdio.h>
// Program execution starts in main()
int main() {
	int a = 6, b = 3;
	// Print formatted text to the screen
	printf("%d", a & b);
	// Return 0 to signal that the program finished successfully
	return 0;
}

Bitwise OR (|)

| compares two numbers bit by bit and produces a 1 in each position where at least one operand has a 1 -- commonly used to turn on specific bits without disturbing the others, such as setting a flag inside a bitmask.

Example: Bitwise OR (|)

// Include standard input/output (printf, scanf)
#include <stdio.h>
// Program execution starts in main()
int main() {
	int a = 6, b = 3;
	// Print formatted text to the screen
	printf("%d", a | b);
	// Return 0 to signal that the program finished successfully
	return 0;
}

Bitwise XOR (^)

^ (XOR) produces a 1 in each bit position where the two operands differ, and a 0 where they match -- a classic use is toggling a bit on or off, or swapping two values without a temporary variable.

Example: Bitwise XOR (^)

// Include standard input/output (printf, scanf)
#include <stdio.h>
// Program execution starts in main()
int main() {
	int a = 6, b = 3;
	// Print formatted text to the screen
	printf("%d", a ^ b);
	// Return 0 to signal that the program finished successfully
	return 0;
}

Bitwise NOT ()

~ is a unary operator that flips every bit of its single operand -- every 1 becomes 0 and every 0 becomes 1 -- which for a signed integer effectively produces its bitwise complement, not simply its negative.

Example: Bitwise NOT ()

// Include standard input/output (printf, scanf)
#include <stdio.h>
// Program execution starts in main()
int main() {
	// Declare a and set it to 5
	int a = 5;
	// Print formatted text to the screen
	printf("%d", ~a);
	// Return 0 to signal that the program finished successfully
	return 0;
}

Shift Operators (<< and >>)

<< shifts all bits left by a given number of positions (equivalent to multiplying by a power of 2), while >> shifts them right (roughly equivalent to integer division by a power of 2) -- both are much faster than actual multiplication or division.

Example: Shift Operators (<< and >>)

// Include standard input/output (printf, scanf)
#include <stdio.h>
// Program execution starts in main()
int main() {
	// Declare a and set it to 4
	int a = 4;
	// Print formatted text to the screen
	printf("%d %d", a << 1, a >> 1);
	// Return 0 to signal that the program finished successfully
	return 0;
}

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