Reading TRS-80 discs (was RE: Archiving old discs...)

From: Eric Smith <>
Date: Tue Sep 14 17:40:39 1999

Tony wrote:
> There was a TRS-80 model 1 Zork that meets this description -- I bought
> it years ago. It was a single-density disk (The model 1 used a 1771
> controller that could only do single desnity), and it was formatted
> strangely 'copy protect' it. It was also a self-booting disk with no
> filesystem as such -- the Zork program just read the text (encrypted
> IIRC) from raw sectors on the disk.

Compressed, rather then encrypted, although I'm sure the resulting
obfuscation was considered a benefit by the designers. And it wasn't
just strings that were read from the disk; the actual game was written
in Z-code, the instruction set for a virtual machine. The only Z-80
code was the Z-code interpreter, which implemented a virtual memory
system in order to make Zork playable on a 32K machine.

The general principles were described in the article "How to Fit a Large
Program Into a Small Machine, or How to Fit the Great Underground Empire on
Your Desk-top", by Mark Blank and Stu Galley, published in Creative Computing
in July 1980. The article may be found at
Received on Tue Sep 14 1999 - 17:40:39 BST

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