GORILLA.BAS: the story of the game that shipped with MS-DOS
How a few hundred lines of BASIC, bundled free with every copy of MS-DOS 5.0, became one of the most played and most edited programs of the early PC era.
In June 1991, Microsoft released MS-DOS 5.0. It brought a better shell, a full-screen editor and, for the first time, a complete BASIC interpreter called QBasic, replacing the old GW-BASIC. Inside that interpreter, among the sample programs, was a small game called GORILLA.BAS.
A game in the box
Nobody bought MS-DOS for the games. But GORILLA.BAS came free with an operating system, on every machine that ran it, and it asked for nothing: no install, no disk change, no manual. You typed QBasic, opened the file, and pressed F5. In the era before everyone had a modem, that was how a great many people met a computer game they owned rather than borrowed.
What GORILLA.BAS actually did
Two gorillas stood on a skyline of coloured blocks. On your turn you typed an angle, then a power, and a dot arced across the screen under gravity and wind. Hit the other gorilla and it exploded; hit a building and you punched a hole out of it, changing the board for the next shot. Two players passed the keyboard between turns.
That is a complete turn-based artillery game — and it was built on real projectile physics, with a wind value that changed every round. For its size it was remarkably deep, which is why it was played far beyond the curiosity of a bundled sample.
The source was the point
QBasic shipped with its sources. GORILLA.BAS was written to be read: the variables were named, the physics was in the open, and the whole game fitted on a few screens. That changed its fate. People edited the gorillas into other characters, changed gravity, added weapons, rewrote the city generator. For thousands of future programmers it was the first real program they understood end to end — and the first they broke on purpose to see what would happen.
Why it stuck
GORILLA.BAS survived because it arrived at exactly the right moment, in exactly the right place, with exactly the right licence: free, universal, and readable. It is remembered less as a game than as an artefact of the DOS era — the moment the computer in the box became something you could play with and, if you wanted, rewrite.
This remake is our way of returning the favour. Twenty-five years on, the same idea still works: two gorillas, a skyline, exploding bananas, and a wind that does not forgive.