Power-electronicsHow-ToBeginner · 4 min read

How to Use Bitwise XOR in Embedded C: Syntax and Examples

In Embedded C, use the ^ operator to perform a bitwise XOR between two integers. It compares each bit of the operands and returns 1 if the bits differ, otherwise 0. For example, result = a ^ b; computes the XOR of a and b.

📐

Syntax

The bitwise XOR operator in Embedded C is ^. It takes two integer operands and compares their bits one by one.

Operand 1: First integer value.
Operand 2: Second integer value.
Result: A new integer where each bit is 1 if the corresponding bits of operands differ, else 0.

result = operand1 ^ operand2;

💻

Example

This example shows how to use bitwise XOR to toggle bits and combine values in Embedded C.

#include <stdio.h>

int main() {
    unsigned char a = 0b10101010;  // 170 in decimal
    unsigned char b = 0b11001100;  // 204 in decimal
    unsigned char result = a ^ b;  // XOR operation

    printf("a = 0b%08X (decimal %d)\n", a, a);
    printf("b = 0b%08X (decimal %d)\n", b, b);
    printf("a ^ b = 0b%08X (decimal %d)\n", result, result);

    // Toggle bits example
    unsigned char toggle_mask = 0b00001111;
    unsigned char toggled = a ^ toggle_mask;
    printf("Toggle lower 4 bits of a: 0b%08X (decimal %d)\n", toggled, toggled);

    return 0;
}

Output

a = 0b10101010 (decimal 170) b = 0b11001100 (decimal 204) a ^ b = 0b01100110 (decimal 102) Toggle lower 4 bits of a: 0b10100101 (decimal 165)

⚠️

Common Pitfalls

Common mistakes when using bitwise XOR in Embedded C include:

Using ^ instead of logical XOR (!= for booleans).
Applying XOR on signed integers without considering sign bits.
Confusing XOR with OR (|) or AND (&) operators.
Forgetting that XOR with the same value twice restores the original value.

#include <stdio.h>

int main() {
    int x = 5;  // 0101 in binary
    int y = 3;  // 0011 in binary

    // Wrong: Using logical XOR (^) on booleans or expecting logical behavior
    // int wrong = x ^ y; // This is bitwise XOR, not logical XOR

    // Correct: Use ^ for bitwise XOR
    int correct = x ^ y;
    printf("Bitwise XOR of %d and %d is %d\n", x, y, correct);

    // Demonstrate XOR property
    int original = 10;
    int key = 7;
    int encrypted = original ^ key;
    int decrypted = encrypted ^ key;  // XOR again with same key
    printf("Original: %d, Encrypted: %d, Decrypted: %d\n", original, encrypted, decrypted);

    return 0;
}

Output

Bitwise XOR of 5 and 3 is 6 Original: 10, Encrypted: 13, Decrypted: 10

📊

Quick Reference

Operator	Description	Example	Result
^	Bitwise XOR	5 ^ 3	6 (0101 ^ 0011 = 0110)
a ^ a	XOR with same value	7 ^ 7	0 (all bits cancel out)
a ^ 0	XOR with zero	9 ^ 0	9 (value unchanged)
Toggle bits	XOR with mask toggles bits	a ^ mask	Bits flipped where mask is 1

✅

Key Takeaways

Use the ^ operator to perform bitwise XOR between two integers in Embedded C.

XOR returns 1 for bits that differ and 0 for bits that are the same.

XORing a value twice with the same number restores the original value.

Avoid confusing bitwise XOR (^) with logical operators.

XOR is useful for toggling bits and simple encryption in embedded systems.