Sixty years of programs
fighting programs.

Timeline

From a lunch-break game on a mainframe to AI-written warriors.

1. 1961

   🧬 Darwin

   At Bell Labs, Victor Vyssotsky, Robert Morris and Doug McIlroy play Darwin on an IBM 7090. Their programs, called "organisms", fight to take over the machine's memory. It's Core War's direct ancestor, 23 years early.

2. 1971

   🐛 Creeper and Reaper

   Bob Thomas at BBN writes Creeper, an experimental program that hops between ARPANET machines printing I'M THE CREEPER: CATCH ME IF YOU CAN. Reaper is written to hunt it down. You could call it the first worm and the first antivirus.

3. 1984

   📰 Core War goes public

   A. K. Dewdney's Computer Recreations column in the May issue of Scientific American introduces Core War, based on the "Core War Guidelines" he wrote with D. G. Jones. It introduces the Imp, the Dwarf and Gemini. Readers start mailing in warriors.

4. 1985

   🦠 A bestiary

   A follow-up column, "A Core War bestiary of viruses, worms and other threats to computer memories", links the game to the real-world worries that were just starting to appear.

5. 1986

   🏆 The first tournament

   The newly formed International Core War Society (ICWS) runs the first tournament and publishes its first standard, ICWS'86. The winner is Mice by Chip Wendell, a replicator that breeds faster than anyone can bomb it.

6. 1988

   📏 ICWS'88

   A revised standard tightens up the rules. For years, "Redcode-88" is the language everyone writes.

7. 1991

   💬 rec.games.corewar

   The Usenet newsgroup opens and the scene goes global. Automated King of the Hill servers follow: mail in a warrior, it fights everyone on the hill, and if it scores well enough it pushes the weakest one off.

8. 1994

   ⚙️ The '94 draft and pMARS

   The ICWS'94 draft adds instruction modifiers (.A .B .AB .BA .F .X .I), A-field indirect modes, SEQ, SNE and NOP. It was never formally adopted, but everyone uses it anyway, including this site. The simulator pMARS becomes the reference and adds P-space: memory that survives between rounds.

9. '90s

   🔥 The golden age

   Imp spirals, Silk-style papers, quickscanners, vampires, core clears, bombers that boot away from their decoys. Hills get so competitive that new warriors need dozens of tricks to survive a single week.

10. 2000s

    🧪 Evolution strikes back

    Programmers build evolvers that breed warriors with genetic algorithms. On the small Nano hill (80 cells, 5 instructions), evolved warriors hold their own against human-written ones. Darwin would be proud.

11. 2020s

    🤖 The machines join in

    Researchers start using large language models to write and evolve warriors. A game invented to pit programs against each other turns out to be a neat benchmark for programs that write programs.

12. Now

    ⚔️ You

    Core War runs in your browser. No install, no mailing list, no waiting for the hill to report back. Write a warrior and earn your first badge.

Hall of Fame

Legendary warriors. The ones with a ⚔️ button are in the arena. Click it to watch them fight their classic rival.

Trivia

Tap a card to flip it.

Glossary

Core War slang, decoded.

Bomb

An instruction (usually DAT) written into enemy territory, hoping an enemy process runs into it.

Bomber / Stone

A warrior that drops bombs over the core at a fixed step. Small and fast. The Dwarf is the original.

Boot

Copying your warrior away from where it was loaded, often leaving a decoy behind, so the enemy attacks the wrong place.

Core

The circular memory the battle takes place in. 8000 cells in Standard rules.

Core clear

Wiping every cell of the core, usually at the end of a fight, to kill anything still hiding. See the Broom.

Cycle

One round of turns: every living warrior executes one instruction.

Decoy

Junk code that makes scanners think they've found you.

Hill

A permanent tournament. New warriors fight everyone on it, and the weakest gets pushed off.

ICWS

International Core War Society. Wrote the '86 and '88 standards and the '94 draft.

Imp

A warrior that crawls through memory by copying itself forward. Also any instruction that behaves like that.

Imp gate

A cell that's constantly being decremented, so any imp that walks onto it breaks.

Imp spiral / ring

Several imps spaced (CORESIZE+1)/N apart, taking turns copying each other. Very hard to kill completely.

KotH

King of the Hill: the automated tournament servers of the '90s and later.

MARS

Memory Array Redcode Simulator: the virtual computer warriors run in. This site has one written in JavaScript.

Nano / Tiny

Hills with a smaller core: Nano has 80 cells and 5 instructions, Tiny has 800 and 20. Fewer tricks fit, so creativity wins.

P-space

Private memory that survives between rounds, so a warrior can adapt.

Paper / Replicator

A warrior that keeps copying itself to new places. Kill one copy and ten more are running.

pMARS

The portable MARS: the reference simulator since the '90s.

Process

One thread of execution. SPL creates more of them. A warrior dies when its last process dies.

Quickscan

A very fast, unrolled scan of a few spots right at the start, hoping to catch the enemy before it gets going.

Redcode

The assembly language warriors are written in.

Scanner / Scissors

A warrior that looks for enemy code (with SEQ, SNE or JMZ) before attacking it.

Score

3 points per win and 1 per tie. Hills rank warriors by their average.

Step

The distance between a bomber's bombs or a scanner's looks. Picking a good one is an art.

Vampire / Pit

Instead of DAT bombs, throw JMPs that send enemy processes into your trap (the pit), where they work for you or die.

Warrior

A Core War program.

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