What is the p-Machine, and why is it like that?
Before we can go into greater detail about what the code in our example (and other programs) actually does, we're going to need a little background on what the p-Machine architecture is, and why it has some of the features that it has...
http://markbessey.blog/2025/05/20/ucsd-pascal-in-depth-the-p-machine/
UCSD Pascal In Depth: Code files
Unlike text files, the code file format is well described in the Apple Pascal Operating System Reference manual. So decoding a code file should be really simple, right? Let's take a very simple "Hello World" program…
http://markbessey.blog/2025/05/18/ucsd-pascal-in-depth-code-files/
#retrocomputing #apple #pascal #psystem
UCSD Pascal: In Depth 3/n
Part 3 - File Formats (text)
What kind of system has a "file format" for text? If you've only worked on modern systems, the idea that a "text file" would be anything other than a bunch of unorganized bytes is probably pretty foreign....
http://markbessey.blog/2025/05/08/ucsd-pascal-in-depth-3-n/
#pascal #retrocomputing #psystem
Oh look - it's a new blog post, an introduction to the USCD p-System Editor, *written on* the UCSD Pascal Editor:
https://markbessey.blog/2025/04/29/ucsd-pascal-in-depth/
Yes, this means that my #Rust #psystem utility can successfully copy files off of the emulator disk image, and convert them into Mac-formatted text, from the frankly bizarre format that's native to the text editor.
Getting files off of the Pascal disk is important, because my next two blog posts are on there. Yes, I used the somewhat weird, modal text editor to write a couple of posts. One's about the editor itself, how meta.
Spoiler: I find it somewhat less ergonomic than vi.
#retrocomputing #pascal #psystem
It's midnight, but I am *finally* "listing" files on an Apple Pascal formatted disk image from my Rust-based filesystem utility.
Which means - I have understood the disk format well enough, and interpreted the filesystem structures properly.
Maybe tomorrow, I can move on to getting some files on/off the disk images.
I had a thought that it might be fun to play around with some UCSD Pascal and p-System programming. I have fond memories of working in Apple Pascal in High School and doing some work in HP Pascal (on the 9000/300 series) at my first job.
There is *a lot* of p-system information on the Web, but it's generally very poorly organized. But I did manage to get an Apple 2 emulator up and running on my Mac, and I found disk images for Apple Pascal 1.3, so I'm now able to actually do some work in that environment.
It is amazing what we put up with in terms of user interfaces back in the day, isn't it? It's certainly a lot nicer running on an emulator that can execute 6502 code hundreds of times faster than an Apple II ever could, though.
I think my intermediate-stage goal here is to write a p-system emulator of my own that runs natively on the Mac. Probably it'll be in Rust, because fighting with Rust is now part of my day job, and I have to get better at it.
