]Applesoft BASIC, in your browser

The BASIC that could have taken the market GW-BASIC owned — two significant characters per variable name, six colours the display half-invents, and floats that answer .1 + .2 with .3 — rebuilt bugs-and-all as a real 16-bit DOS program and run here under DOSBox. Nothing to install. Click a program below and it loads and runs itself.

Start typing BASIC

The classic ] prompt, with a helper panel beside it: one-click sample programs, commands to try, and the famous bugs explained.

Open the console →

Open the IDE

A windowed front end in 80×43 text mode — menu bar, editor, program listing, and a Machine pane showing zero page and the control stack. F5 runs, F10 opens the menus.

Open the IDE →

The screen is the Apple's

The forty-column text screen, with INVERSE and FLASH HGR with the four text lines under the picture Eighty columns after PR#3

Forty columns, then HGR with the prompt in the four lines under the picture, then PR#3. Real BIOS text modes and VGA mode 13h, painted from the Apple's own page memory.

One click, and it runs

SNAKEA game. Steer with I J K M, quit with Q. MANDELThe Mandelbrot set, in four colours. DRAGONThe dragon curve, drawn to fit. FERNBarnsley's fern — four affine maps. JULIAA Julia set, banded by escape time. SIERPSierpinski's triangle, by the chaos game. SPIROA spirograph curve that closes. CUBEA rotating wireframe cube. MOIREInterference — and an invented colour. LORESAll sixteen lo-res colours. HGRDEMOThe hi-res colour rules themselves. HGRSHAPShape tables: DRAW, XDRAW, ROT, SCALE.

Why the bugs are the point

Ask it for PRINT .1 + .2 and it says .3 — not because anything is rounded for show, but because Applesoft carried nine significant digits in its 5-byte floats, and that is what nine digits gives you.

Name a variable TOTAL and LIST shows it as TO TAL, because the tokenizer finds the keyword hiding inside. Trap errors in a loop and ONERR leaks a stack frame every time, killing the program after exactly sixty of them, and ?OUT OF MEMORY ERROR is spelled exactly the way the machine spelled it.

All of it is reproduced deliberately and checked against the genuine Applesoft ROM running in an Apple II emulator — seventeen of twenty test programs come out byte-identical, and the differential harness in the repository shows its work. Each misfeature can be switched off individually. This is an act of preservation, not nostalgia for its own sake.

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