Making the Matrix Screensaver in C on a PDP-11/83

Highlights

- Bringing a vintage PDP-11/83 Minicomputer back to life with BSD Unix and K&R C
- Showcasing a custom-built MATRIX screensaver that uses classic VT220 control sequences
- Demonstrating four different retro-style “screensavers,” including Conway’s Game of Life
- Exploring the shared lineage between 211BSD and modern macOS through easy cross-compilation

Why to Watch

- Learn how to write and compile retro C code on authentic PDP-11 hardware
- See how low-level terminal control codes enable surprisingly dynamic on-screen visuals
- Discover tips and tricks for preserving a usable UNIX environment after custom programs exit
- Experience a hands-on approach to bridging decades of computing history in one fun project

[asdfasdfasdf]

The green phosphors on that old CRT brings back one scary memory. Turns out staring at all that green for long periods of time and driving home at night makes the lettering on freeway signs appear pink. My optometrist tells me it's a "Color Adaptation". My photo-receptors (specifically the ones sensitive to green light) become desensitized or fatigued due to prolonged stimulation. It's apparently normal with no lasting aftereffects. I guess you could say I had suffered a temporary form of burn-in ;-)

[Avenger]

I’m with you. “Do what is right, let the consequence follow” was always good advice.

[TheMKoussa]

You're the staff dev we all hope to work with! So much knowledge and willingness to share!

[volvo]

Oh that green phosphor image retention looks amazing in that intro shot.

Btw beautiful truck!

[natersoz]

Nice video, nice code.
My first job out of college was factory automation on a pdp-11.
Pretty sure the “OS” was proprietary to the group I worked for. It has been almost 40 years. I still keep in touch with some of them. This video was like therapy to me. So nice.

[matt_kelly]

I remember writing this screensaver on a new MacBook when Swift first came out and I wanted to try a simple project. It's clearly a lot different since it's not a terminal app, but I didn't wind up finishing it. I think I'm going to make it a goal to finish it, at least to the point where I originally wanted it (without the trails). Thanks for the inspiration!

[aceldama]

this triggered core memories in me. i plowed so much of my youth into creating ascii games and scrolling patterns. right in the nostalgia.

[vrewq]

I used to use that VT220 book but for games I moved onto using the "Curses" library for compatibility with the Wyse and Qume using Termcap

[Thatdavemarsh]

Love it. Reminds me of the old BBS days and screen painting with characters and codes. So good! Thanks!

[metaleggman]

That phosphor trail is part of the reason I always loved playing vector game ports on my windows 3.11 machine. It isn't quite the same as a true vector display (I was lucky enough to play one or two in the past), but it emulates it well enough that you remember that electrons are whizzing around and exciting phosphors. My 93 Packard Bell display is still in good kit, but a bit dull in brightness, so I usually have to play in a darker environment, but man, it still looks awesome.

[LoesserOfEvils]

The retrocoding adventure reminded me of the opening credits of seasons 1-2 of Lost in Space. Your flashing stars made me nostalgic for the flashing buttons, i.e., circles and squares.

[ElectricRob]

Hah, love your statement "don't have any corpses on display" about your actually working computers!

[AllenCavedo]

These PDP videos are very interesting. I worked with PDP 11/34’s back in 1980. Bring back memories.

[WarttHog]

Dude, your GARAGE garage is immaculate! I appreciate all the car references in this video. I've always wondered why more of us computer nerds aren't also into cars. Someday you should give us a tour of your wheels!

[andrebaskin]

This brings back memories of rewriting a screen drawing library on VMS from hand coded escape codes to SMG. The big win from the users this was the ability to send the current screen to a printer. This allowed them to print a screen, mark it up with the changes they wanted and other notes, and fax it to the person making the changes.

[skunked]

Dude, that is a really amazing truck!

[terminalpsychosis]

Classic, fun project. Fun idea with the sine wave. Makes it look really organic.

[davidswanson]

Dave, that is so cool, really brings back memories of working with terminals with long persistent phosphor in the military. I used to work with a Tektronix 4010 terminal which could draw lines but they had to redraw because the image faded out. I miss the old consoles with the switches and lights. I wish I could get something like your DEC console to add to my computer. The old days when you needed to load a program from tape and flick the IPL switch 😊 Initiate Program Load to install the OS. My first mainframe was a Sperry Univac 418 series III with at least a 30 foot row of reel to reel tape drives and a noisy line printer.

[framegrace]

Just in case someone didn't got it from the video as is not explictly said, this works on almost any modern terminal emulator on Linux/Mac. A subset of vt220 codes were selected as the ANSI standard, and all of them work on any modern terminal app. It has been extended to support even 24bit color.

[NuntiusLegis]

When I got a green monitor for my C64 a few years ago, the first thing I did was programming a Matrix-like effect in BASIC; it doesn't display random characters, but reads the actual memory cells and interprets that as PETSCII codes (which include more useful graphics and control characters than ASCII), resulting in occasional color (brightness in monochrome) changes and cursor repostitioning for interesting extra effects.