SPACEWAR! Critical Code Studies · PDP-1 · 1962
Digging deeper into the MIT-AI port

SPCWAR: the game that wrote its own history

At the MIT AI Lab the game was kept alive on the PDP-6 and PDP-10 under the lab's own operating system, ITS, deep into the 1970s. Along the way it changed its name eight times and, more remarkably, began to record its own history in its own comments.

eight names
WAR to SPCWAR

One program, many titles

The MIT-AI Spacewar! is a different object from the classic PDP-1 releases. It is a continuously maintained program, edited by whoever was keeping it running, and its title drifted as it went. The source records the line plainly at the top:

WAR → SWAR → SUPER → STAR → SPACE → SPACE4 → NSPACE → SPCWAR

By the mid-1970s the maintainers named in the file were Ken Harrenstein (KLH@MIT-AI) and two others signing as GMP@MIT-MC and CBF@MIT-ML. This was code as a shared, living object, handed from hand to hand on the ITS timesharing system rather than pressed onto a paper tape and frozen.

the consoles
9 April 1976

New hardware for an old game

The game was still being built in hardware as well as software. On 9 April 1976, fourteen years after the original, the source notes that "the new nine-bit Space-War consoles were completed". They were designed and built by Kevin Hunter; Ken Harrenstein and Lee Parks then "spent ten hours wiring the new consoles into the PDP-6 alternate data switches bank". The modification log that follows, running through the spring and autumn of 1976, shows the game still growing new features: per-ship display lists, the ability to "dynamically alter ship designs used during a game", shields, and black holes.

a self-documenting variorum
The reading

The code as its own historian

What makes this version important for Critical Code Studies is that it documents itself. The source opens with its own genealogy of names, then keeps a dated record of modifications, version by version, signed by their authors: version 139 on 13 April 1976, 141 on the 16th, 142 on the 17th, 148 on the 29th, 153 in October. The program even reports its own state at assembly time, printing "This is version ..." as it is built, and late versions add a "Vector of Mysteries" holding the VERSION and the OPTIONS with which the game was assembled.

Elsewhere on this site we reconstruct the order and difference of versions from scattered listings and tapes. Here the hackers did that work themselves, inside the artefact, leaving a running commentary on their own changes. The code is not only the object of a history; it is, partly, the writing of one. That a game maintained for fun should keep so careful a record of itself is an indicator that these programmers understood computer-based game play as something worth documenting.

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