Core War — Linked Overview

Concise primer with live links, mechanics, runnable samples, and strategy hooks.

Sharpened blurb (with links)

Core War (1984) is a programming battle where players write assembly-like “warriors” in Redcode that execute on a virtual CPU called MARS (Memory Array Redcode Simulator). Warriors share a circular memory (“core”) and try to kill the opponent by forcing its processes to execute DAT. Classic archetypes include bombers, replicators/papers, and imps; you’ll also see scanners, stones, and hybrids. Many people test with the community simulator pMARS. The strategy space—timing, stride math, decoys, and process scheduling—makes Core War a deep algorithmic game.

Note: “imps,” not “impulses.”

Key mechanics (one level deeper)

• Core: circular memory; addressing wraps around (mod arithmetic matters).
• Process model: round-robin; SPL forks new processes. A warrior dies when it has no processes left.
• Win condition: last warrior with any live process wins; max-cycle draws are possible.
• Bread-and-butter ops: MOV ADD SUB MUL DIV MOD JMP JMZ JMN DJN CMP/SNE SLT SPL DAT. Addressing includes immediate #, direct (default), and indirect / pre- / post-indexed modes (@ < > in ’94). Instruction modifiers like .A .B .F .X .I define which fields are affected. See the Redcode reference and ICWS ’94 draft.

Tiny, runnable examples (ICWS ’88-style syntax)

Imp (ever-marcher)

;name Imp
        ORG     imp
imp     MOV     0, 1

Dwarf (classic bomber)

;name Dwarf
        ORG     start
start   ADD     #4, 3
        MOV     2, @2
        JMP     -2
        DAT     0, 0

Why it works: ADD advances the bombing pointer; @2 uses it indirectly. Choosing a stride relatively prime to the core size maximizes coverage (see Dwarf analyses).

Strategy hooks you can explore

• Stride design and coverage math for bombers (Dwarf lineage).
• Process economy: heavy SPL trees vs. minimalist stones/imps.
• Scanners & oneshots: probe first, then slam (great primer: Anatomy of the Scanner).
• Imp tech: rings/spirals and imp-gates (see Imps, Rings & Spirals).
• Tooling: simulate and debug with pMARS.

Links: Wikipedia, ICWS ’88/’94, pMARS, Redcode reference, classic strategy articles. All external resources belong to their respective owners.