Skip to Content

A stick figure smiling

Here's a preview from my zine, How Integers and Floats Work! If you want to see more comics like this, sign up for my saturday comics newsletter or browse more comics!

Image of a comic. To read the full HTML alt text, click "read the transcript".

browse more comics! get the zine!
read the transcript!

title: how bitwise operations are used

panel 1

Binary formats often pack information into bytes very tightly to save space.

Bitwise operations are what you use to encode or decode data into a binary format.

Here’s how and, or, left shift, and right shift are used for encoding and decoding.

panel 2: check/set bit flags

set bit flags with or: x = x | 0x04

check bit flags with and:: if (x & 0x04 != 0) {}

(snippets are C code)

panel 3: bit masking

“bit masking” means using & to set some bits in a number to zero. For example, & 0xFFFF zeroes all except the last 16 bits:

masked = x & 0xFFFF

panel 4: unpack/pack bits

for example, to unpack the leftmost 2 bits of a byte: first_two_bits = x >> 6 (>> is right shift)

for example, to pack 01 into the left 2 bits of a byte: result = (1 << 6) (<< is left shift)

panel 5: checksums and encryption

xor is used for checksums and encryption. Here’s what encrypting with xor in Python looks like:


text = b”secret message” for (t, k) in zip(text, key): encrypted += t ^ k ```

Saturday Morning Comics!

Want another comic like this in your email every Saturday? Sign up here!

I'll send you one of my favourite comics from my archives every Saturday.
© Julia Evans 2024 | All rights reserved (see the FAQ for notes about licensing)