Thread by @BacteriaMage

Recently I've gotten really interested in the #Apple1. The forerunner to the much better known Apple II and the machine that originally launched @Apple in 1970s.

Here are some of the more interesting points on my adventure. #Thread

It's such a simple machine that a minimally technical article I read earlier this year had enough details to write a simple #emulator.

Which I ended up doing; my very first attempt at creating one. #MOS6502

Here it is running @stevewoz's original 256-byte "monitor" firmware/OS.

My emulator is just a console app with a command line to control the emulation.

The actual I/O text streams for the emulated machine are just pushed through a local socket connection.

#PuTTY works great as a front end.

A real Apple-1 would need a TV screen and keyboard.

Wozniak didn't have access to an #assembler so he wrote the monitor and later a 4k BASIC interpreter on paper then assembled them manually by hand. #Awesome

I had to try this; coding a short program this way is fun. I imagine anything more complex would quickly become tidious.

Apple-1s came in at least 4K and 8K varieties.

An 8K with an optional expansion card could run #BASIC loaded from an audio #cassette.

Modern replicas often have 48K RAM plus BASIC in ROM.

My simple settings file format allows emulation of a variety of hardware configurations.

What I've come to realize is very little software was specifically made for the Apple-1. This was the wild west and most code was BASIC or processor-specific assembly.

Everyone shared what they had and adapted the code to run on whatever "microcomputer" platform was available.

I really like this #StarTrek themed BASIC game. Like #VGATrek and others it's a clone of a 1960s teletype game played on university mainframes.

Impressive since it uses every RAM byte for either code or run-time variables.

Not uncommon to see A1 software use every last byte.

I also like this "Hamurabi" BASIC game. Likely a simplified adaptation of "The Sumerian Game" from the 1960s.

That's a fascinating one; worth reading this article.

acriticalhit.com/sumerian-game-…

You can find Apple-1 specific binary dumps or audio recordings of various BASIC games on AppleFritter and elsewhere.

These were likely all originally copied from hobbyist focused magazines and later the famous book "BASIC Computer Games" by Creative Computing.

Not A1 specific.

I built a debugger into my emulator to help with #ReverseEngineering code.

I'm not the first to attempt to #disassemble Woz's BASIC but still interesting.

Small unused pockets and random NOPs really illustrate how it was manually constructed, debugged, and patched.

I've dug deep enough to be able to dump the grammar tables.

A final interesting mystery are unused COLOR and PLOT statements buried in there.

The Apple-1 displayed monochrome text so what could this have been for?

Was Wozniak already thinking about graphics or the Apple II?

I don't plan to release my emulator for now.

But, if you want an easy way to experience the Apple-1 then try the JavaScript based Apple 1js right in your browser.

It's more accurate than mine anyway and has a bunch of software "tapes" built right in.

scullinsteel.com/apple1/