1200 Baud Archeology: Reconstructing Apple I BASIC from a Cassette Tape [pagetable.com]

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The Apple I is extremely rare. Only 200 were built, and less than 100 are believed to be in existence. Neither Steve nor Woz own an Apple I any more, and neither does Apple Inc. The cassettes are even rarer, as not every Apple I came with one. There has not been a dump of the tape until 2002, when Achim Breidenbach of Boinx Software got an MP3 recording of an original Apple 1 BASIC tape by Larry Nelson, an Apple I owner, and, with a little help from his father (who worked with an Apple I back in 1976), managed to decode it by writing a program – in GFA BASIC on an Atari ST. Here is a screenshot of the visualization this program could provide:

Achim wrote an Apple I emulator, included a commented disassembly of his Apple I BASIC dump, and published it on the internet. Other people continued working on the disassembly and changed instructions that they thought were mistakes in the dump. The only dump that can be easily found today includes these changes. It was time to analyze the tape again and get an authoritative dump of the 4096 bytes.