Swap Variables Without a Temp: The XOR Trick Explained

Understanding XOR

In digital computers every value is represented in binary, using only the digits 0 and 1. The XOR (exclusive OR) operation yields 0 when the two bits are the same and 1 when they differ.

Binary example

Consider the two 4‑bit numbers 1001 (decimal 9) and 1100 (decimal 12). Applying XOR bit‑by‑bit produces:

1001
1100
----
0101

The result 0101 corresponds to decimal 5.

Swapping two integers with XOR

The XOR operation can exchange the values of two variables without allocating a temporary storage location. The sequence of three XOR assignments works as follows:

Combine the two values: a = a ^ b Recover the original value of a into b: b = a ^ b Recover the original value of b into a: a = a ^ b After these steps, the variables a and b have swapped their original contents.

C code demonstration

int handsome = 1;
int rich = 5;
handsome = handsome ^ rich;
rich = handsome ^ rich;
handsome = rich ^ handsome;

Running this snippet changes handsome from 1 to 5 and rich from 5 to 1, achieving the swap without any extra variable.