Home to The Digital Organism Anatomy Field Guide, ICWS-94 virtual machine specifications, tactical engineering, and CoreWar archives.
An in-depth anatomical and computer science monograph series dissecting the five foundational digital organism species inhabiting the 8,000-cell Von Neumann memory torus—mapping every line of Redcode to its biological organelle glyph.
Composed of a single instruction—"MOV.I 0, 1"—the Imp is the smallest autonomous organism in CoreWar. By copying itself one cell forward and stepping into its own replica on the next cycle, it marches endlessly around the 8,000-cell torus.
Anchored permanently within a compact 4-cell membrane, Dwarf extends an indirect pointer (@) like a stinging tentacle to hurl lethal DAT spore bombs (◆) into every 4th cell across the 8,000-cell core—the foundational ancestor of all Stone warriors.
Combining the mitotic SPL instruction (❖) with a high-speed dual pre-decrement transcription loop, Mice / Paper projects complete clones of its multi-line genome across memory—overwhelming stationary Stone bombers through exponential swarm growth.
Unlike blind Stone bombers, the Scanner possesses an optical sensory organelle (◉ CMP / SEQ / SNE). It leaps across empty memory in 3-cycle saccades, unleashing lethal spores or SPL stun venom only the instant it detects foreign code.
Instead of killing enemies outright with DAT bombs, the Vampire casts calibrated JMP "Fangs" across memory. Any enemy PC that steps on a Fang is abducted into "The Pit"—an SPL 0 prison that hijacks the victim's process queue and enslaves its CPU cycles to power an Imp-Gate.
The battlefield of CoreWar—known as the Core—is powered by a virtual processor called MARS (Memory Array Redcode Simulator). Under the standard ICWS-94 ruleset, the Core consists of 8,000 contiguous memory cells (addresses 0 through 7999). All arithmetic and pointer evaluations wrap around modulo 8,000, forming a seamless circular ring where address -1 maps to 7999.
Unlike conventional CPUs, every address in Redcode is strictly relative to the currently executing instruction (Program Counter). Because there are no absolute addresses, all Redcode programs are inherently Position-Independent Code (PIC)—meaning a warrior can copy itself anywhere in memory and continue running without relocation tables. Furthermore, ICWS-94 introduces seven instruction modifiers (.A, .B, .AB, .BA, .F, .X, .I), allowing programmers to target specific operand fields or copy entire instructions at once.
When engineering a Stone bomber or a Scanner, choosing the optimal pointer step size is a mathematical art. In an 8,000-cell core, a naive step of 8 or 10 leaves wide gaps where small enemy loops can hide indefinitely. Competitive warriors use mathematically derived step constants (such as 2365, 3039, or 3359) that maximize worst-case coverage density across the core before repeating modulo cycles.
At the opposite end of the spectrum lies the Imp-Spiral (or Imp-Ring). While a standard 1-point Imp (MOV 0, 1) dies as soon as its lead instruction is bombed, a 3-point Imp-Spiral executes MOV.I 0, 2667 across three interleaved processes (since 2667 * 3 = 8001 ≡ 1 mod 8000). Because the three points continuously feed instructions to one another across the core, standard DAT bombers cannot kill them; defeating an Imp-Spiral requires a dedicated Imp-Gate (such as JMP 0, <-2) that shreds incoming instructions every single cycle.
The largest online CoreWar community. Contains warrior archives, KOTH (King of the Hill) competitions, forums, and extensive documentation.
VISIT →Submit your warrior to the online KOTH server and see how it ranks against warriors from around the world. The ultimate test of your Redcode skills.
VISIT →The reference Redcode simulator. pMARS (portable Memory Array Redcode Simulator) is the standard tool used by the CoreWar community for testing and competing.
VISIT →You are here! Our browser-based IDE provides an interactive environment for writing, testing, and visualizing Redcode warriors.
OPEN →The official Redcode language specification from 1994. This is the definitive reference for all instruction behaviors, addressing modes, and modifiers.
VISIT →A comprehensive tutorial covering the basics of Redcode programming. Perfect for those who have completed our Academy and want to go deeper.
VISIT →A.K. Dewdney's original article that introduced CoreWar to the world. This is where it all began.
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