Whitespace

Whitespace is an esoteric programming language created in 2003 by Edwin Brady and Chris Morris at the University of Durham. Its unique characteristic is that only whitespace characters—spaces, tabs, and linefeeds—are meaningful. All other characters are completely ignored, treated as comments.

History & Origins

Whitespace was released on April 1st, 2003, and announced on Slashdot. Most readers assumed it was an April Fool’s joke, but the language was (and is) completely real and functional. The timing was deliberate—what better day to release a language that inverts the normal rules of programming?

The Creators

Edwin Brady and Chris Morris, both at the University of Durham, created Whitespace. Brady is perhaps better known for creating the Idris programming language, a dependently-typed functional language. The same mind that gave us cutting-edge type theory also gave us a language of invisible instructions.

Why Whitespace?

The language is a commentary on how most programming languages treat whitespace: as insignificant formatting that helps humans read code. Whitespace flips this convention entirely—the characters humans can see are meaningless, and the invisible characters carry all the meaning.

How It Works

The Three Characters

Whitespace uses exactly three characters:

Everything else in a Whitespace program is ignored.

Stack-Based Architecture

Like Forth and Brainfuck, Whitespace is stack-based. It operates on a stack of arbitrary-precision integers, meaning there’s no limit to how large numbers can grow (within memory constraints).

The language also provides a heap for random-access storage, making it more powerful than pure stack-based languages.

Instruction Modification Parameter (IMP)

Instructions in Whitespace begin with an Instruction Modification Parameter (IMP) that determines the category of the operation:

Commands

Stack Manipulation (IMP: [Space])

Arithmetic (IMP: [Tab][Space])

Heap Access (IMP: [Tab][Tab])

I/O (IMP: [Tab][LF])

Flow Control (IMP: [LF])

Number Encoding

Numbers are encoded in binary using space for 0 and tab for 1, prefixed with a sign bit (space for positive, tab for negative) and terminated by a line feed.

For example, to push the number 72 (ASCII ‘H’):

• Sign: [Space] (positive)
• Binary: [Tab][Space][Space][Tab][Space][Space][Space] (1001000 = 72)
• Terminator: [LF]

Label Encoding

Labels are encoded similarly to numbers but without a sign bit—just a sequence of spaces and tabs terminated by a line feed.

The Polyglot Potential

Because all visible characters are ignored, a Whitespace program can be embedded invisibly within:

• Other programming language source code
• Plain text documents
• HTML/CSS files
• Any text file with significant whitespace

This makes Whitespace popular for:

• Steganography: Hiding programs in plain sight
• Polyglots: Programs valid in multiple languages
• Obfuscation challenges: Where finding the hidden program is part of the puzzle

File Extensions

Whitespace source files typically use:

• .ws - Most common
• .wspace - Alternative
• .whitespace - Explicit

Running Whitespace

Various interpreters exist:

• Haskell reference implementation - The original
• Python implementations - Many available on GitHub
• C implementations - For speed
• Online interpreters - For experimentation

For this tutorial, we use the esolang/whitespace Docker image for consistent cross-platform execution.

Viewing Whitespace Code

Since the code is invisible, you need special tools to work with it:

1. Hex editor: Shows the actual bytes (0x20, 0x09, 0x0A)
2. cat -A (Unix): Shows tabs as ^I and marks line endings
3. od -c: Shows all characters including whitespace
4. Syntax highlighters: Some editors have Whitespace modes that colorize the invisible characters

A Word of Caution

Whitespace is intentionally unusual. It’s designed for:

• Exploring the concept of significant whitespace
• Steganography and polyglot programming
• Programming challenges and puzzles
• Having fun with conventions

It is not designed for:

• Production code
• Practical applications
• Teaching beginners to program

Continue to the Hello World tutorial to write your first (invisible) Whitespace program.