Welcome to decuser's blog

Topics on this blog include computing, retro-computing, operating systems, math, and whatever other technical subjects I happen to be exploring that I find interesting enough to take and share notes about.

Posts

• Aug 14, 2026 aiki programming-languages ai education

  Aiki: First Public Alpha

  I've put the first public alpha of Aiki on GitHub.

  Aiki is a small experimental programming language I've been working on for the past several months. I describe it as both a programming language and a learning field: an environment designed to make computational relationships visible enough to inspect, experiment with, and reason about.

  The current release is v0.4.0-alpha. It includes the interpreter, standard library, documentation, examples, tests, validation machinery, and the project's engineering record. Intel/amd64 release archives are available for Linux, Windows, and macOS.

• Aug 8, 2026 unix unix-v6 lions pdp-11 opensimh

  Lions Laboratory: A Sixth Edition UNIX Laboratory for OpenSIMH

  As a follow-up to my note on setting up a Sixth Edition UNIX laboratory in OpenSIMH, I have now put the complete laboratory repository on GitHub:

  decuser/lions-laboratory

  The repository contains the V6 distribution materials, OpenSIMH configurations, PDP-11/40 and peripheral documentation, known-good system checkpoints, and the working notes I have accumulated while reading Lions and experimenting with the system.

• Aug 8, 2026 unix research-unix v6 dec

  Getting DOS-11 V004A Running on a PDP-11/40

  Getting DOS-11 V004A Running on a PDP-11/40

  I did not set out to install DOS-11.

  I have been working with Sixth Edition UNIX on a simulated PDP-11/40, partly to understand the system itself and partly to get closer to the environment described by Lions. That inevitably led downward. Reading the V6 source means reading PDP-11 assembly, and reading PDP-11 assembly means spending some time with the tools and conventions that existed around the machine before and alongside UNIX.

  That led me to PAL-11R, DEC's relocatable assembler for the PDP-11, and from there to DOS-11.

• Jul 24, 2026 unix research-unix v6

  Setting Up UNIX—Sixth Edition: An OpenSIMH Laboratory for Reading Lions

  This note covers building a complete, restorable Sixth Edition UNIX laboratory in OpenSIMH for reading John Lions’ A Commentary on the UNIX Operating System. First, the reader is led through restoring the original V6 distribution from tape to RK05 disk images. Next, the kernel is reconfigured and rebuilt for the PDP-11/40 and the simulated devices used in the laboratory. The remaining source and documentation filesystems are then installed, the required special files are created, and the completed system is verified and archived as a restorable baseline.

  The note explains each step of the process in detail and connects Lions’ commentary and numbered source listing to the corresponding files and configured kernel in the running V6 system.

• Jan 25, 2026 go tools github-pages

  Migrating from Jekyll to a custom static site generator

  Replaced the Jekyll-based blog with a custom static site generator written in Go.

• Jan 25, 2026 tools go

  dex - directory comparison tool in Go

  Released dex, a Go port of my Python dircmp utility. Clean architecture, static binaries, no dependencies.

  Compares two directory trees and sorts files into five buckets:

  1. Exact match — same path, same content
  2. Modified — same path, different content
  3. Same content, different path
  4. Only in src
  5. Only in dst

  Also finds duplicates within a single directory.

  dex [options] <dir>           # find duplicates
  dex [options] <src> <dst>     # compare directories
  

  Options: -a hidden files, -r recurse, -f fast digest, -b brief, -l full digests.

  Prebuilt binaries for Linux and macOS in the releases.

• Nov 3, 2025 retro assembly videos

  Bit by Bit - E10.1 - Assembly Lines ch. 7 - addressing modes

  

  In this first of two episodes on ch. 7, we're going to look at how you use different addressing modes to get data from memory.

  Here's a link to the playlist:

  https://www.youtube.com/playlist?list=PL_z8XUfqFSXHvJ5E5r80ZmMN7LRcCI0Zx

  Enjoy!

• Oct 20, 2025 retro assembly videos

  Bit by Bit - E9.1 - Assembly Lines ch. 6 - I/O Using the Monitor and Keyboard

  

  This is part one of two dealing with I/O. In this episode, we'll track along with Assembly Lines ch. 6 and do some paddle reading (mouse). We'll explore the assembly instruction CMP and try to keep the lessons constrained to ~30 mins or thereabouts.

  Here's a link to the playlist:

  https://www.youtube.com/playlist?list=PL_z8XUfqFSXHvJ5E5r80ZmMN7LRcCI0Zx

  Enjoy!

• Oct 20, 2025 retro assembly videos

  Bit by Bit - E9.2 - Assembly Lines ch. 6 cont. - keys and strobing

  

  In this second of two episodes on ch. 6, we're going to look at how to read the keyboard, with and without clearing the strobe.

  Here's the link to the referenced Apple II Reference Manual

  Here's a link to the playlist:

  https://www.youtube.com/playlist?list=PL_z8XUfqFSXHvJ5E5r80ZmMN7LRcCI0Zx

  Enjoy!

• Oct 18, 2025 retro assembly videos

  Bit by Bit - E6 - Bits in Bits Out

  This, the 6th episode of bit by bit shows how to get information into and out of the AppleWin emulated Apple IIe. Shift-INS to paste and PR#1 to print (know where to find your printout... spoiler, it's in .PlayonLinux/AppleWin/.../applewin/printer.txt)

  Here's a link to the playlist:

  https://www.youtube.com/playlist?list=PL_z8XUfqFSXHvJ5E5r80ZmMN7LRcCI0Zx

  Enjoy!