Iconography of the X Window System: the boot stipple
For the uninitiated, what are we looking at? Could it be the Moire Error from Doom? Well, no. You are looking at (part of) the boot up screen for the X Window System, specifically the pattern it uses as the background of the root window. This pattern is technically called a stipple.
What you're seeing is pretty important and came to symbolize a lot for me as a computer practitioner.
Matt T. Proud
The X bootup pattern is definitely burnt onto my retina, as it probably is for a lot of late '90s, early 2000s Linux users. Setting up X correctly, and more importantly, not breaking it later, was almost an art at the time, so any time you loaded up your PC and this pattern didn't greet you, you'd get this sinister feeling in the pit of your stomach. There was now a very real chance you were going to have to debug your X configuration file, and nobody - absolutely nobody - liked doing that, and if you did, you're lying.
Matt T. Proud dove into the history of the X stipple, and discovered it's been part of X since pretty much the very beginning, and even more esoteric X implementations, like the ones used by Solaris or the various commercial versions, have the stipple. He also discovered several other variants of the stipple included in X, so there is a chance your memory might be just a tiny bit different.
The stipple eventually disappeared at around 2008 or so, it disappeared as part of the various efforts to modernise, sanitise, and speed up the Linux boot process on desktops. On modern distributions still using X, you won't encounter it anymore by default, but in true X fashion, the code is still there and you can easily bring it back using a flag specifically designed for it, -retro, that you can use with startx or your X init file.
There's a ton more information in Proud's excellent article, but this one paragraph made me smile:
I will remark that in spite of my job being a software engineer, I had never spent a lot of time looking at the source code for the X Server (XFree86 or X.Org) before. It's really nuts to see that a lot of the architecture from X10R3 and X11R1 still persists in the code today, which is a statement that can be said in deep admiration for legacy code but also disturbance from the power of old decisions. Without having looked at the internals of any Wayland implementation, I can sympathize sight unseen with the sentiments that some developers have toward the X Window System: the code is a dead end. I say that with the utmost respect to the X Window System as a technology and an ecosystem. I'll keep using X, and I will be really sad when it's no longer possible for me to do so for one reason or another, as I'm extremely attached to it quirks. But it's clear the future is limited.
Matt T. Proud
We all have great - and not so great - memories of X, but I am really, really happy I no longer have to use it.