Old Vintage Computing Research

Now that our 1987 Canon Cat is refurbished and ready to go another nine innings or so, it's time to get into the operating system and pull some tricks. As you'll recall from our historical discussion of the Canon Cat, the Cat was designed by Jef Raskin as a sophisticated user-centric computer but demoted to office machine within Canon's typewriter division, which was tasked with selling it. Because Canon only ever billed the Cat as a "work processor" for documents and communications, and then abruptly tanked it after just six months, it never had any software packages that were commercially produced. In fact, I can't find any software written for it other than the original Tutor and Demo diskettes included with the system and a couple of Canon-specific utilities, which I don't have and don't seem to be imaged anywhere.

So this entry will cover a lot of ground: first, we have to be able to reliably read, image and write Canon disks on another system, then decipher the format, and then patch those images to display pictures and automatically run arbitrary code. At the end we'll have three examples we can image on any PC 3.5" floppy drive and insert into a Cat, turn it on or hit DISK, and have the Cat automatically run: a Jef Raskin "picture disk," a simple but useful dummy terminal, and the world's first (I believe) Canon Cat, two-disk, slightly animated and finely dithered, slideshow graphics demo!

But before we get to pumping out floppy disks, we first need to talk about how one uses a Cat. And that means we need to talk a bit about Forth, the Canon Cat's native tongue. And that means we should probably talk more about the operating system too. Oh, and we should go down to CompUSA and buy a brand new floppy drive while we're at it.

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It's been awhile since I've stripped the copy protection off a Commodore 64 software package. This weekend I had a reason to. I should point out a couple things as preamble. First, my parents insisted I would not rot my brain with games (much), so we had a lot of educational titles for our C64, and second, my wife is a high-school English teacher. I kept a number of packages from back then and one of them was a secondarily acquired copy of DesignWare's The Grammar Examiner from 1984, something like a mashup between a board game and Strunk and White's Elements of Style, where you get to edit a fictional newspaper and fix all the typos and bad punctuation in your quest to become editor-in-chief.

I rather liked it back in the day. Don't judge. My wife -- who used Commodores as a girl in the Australian school system but not this particular title -- enjoyed it even more than I thought she would, enough so that she occupied VICE on the Talos II playing it all afternoon and prevented me from writing this.

The Grammar Examiner plays well enough on my real Commodore 128DCR, though it's a very slow loader, and I only have an original disk which I'd like to preserve. (My original original copy disappeared a while back, though I've had this particular one at least a couple decades.) A quick sector-by-sector D64 image using a ZoomFloppy yielded a number of apparently intentionally bad sectors typical of early 1980s copy protection, but even with the error information the program's loader just plain hung up in VICE trying to boot the copy. Yes, a nibbled raw copy of the GCR would work and I imagine people have made one of this title, but we'd also like to speed up the process instead of burdening the emulator further (and it would be nicer on the real system too).

So in this post we'll explore the loader routine, decrypt and extract it, figure out how the copy protection is implemented and work around it, and then pull out the payload it reads for a faster start. While we're at it, let's look briefly at the program itself, an interesting example of Forth programming "in the large" on 1980's home computers.

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