The v4 tape in the Unix history repo
H.2215 (Ferrer) | Day 2 | 11:20 - 11:35 | Speakers: Diomidis Spinellis
Abstract
In 1974 Ken Thompson sent a copy of the then-current Unix distribution to Marin Newell. Fast forward to to July 28th, 2025. In a storage closet of the Robert Ricci’s Flux Research Group at the Merrill Engineering Building Aleks Maricq a research associate found a tape labeled v4 Unix among the documents of Jay Lepreau. This could be significant, because no other version of its source code have survived. The finding was widely reported on the web and even broadcast TV. To avoid high-altitude cosmic radiation and airport scanner damage lab members Jon Duerig and Thalia Archibald undertook an 11 hour drive it to the Computer History Museum in December 2025. There it was decoded and made available using a sophisticated analog to digital pipeline. A few days later, I integrated the tape's contents in the Unix History Repository. This makes available on GitHub a repository, covering the period from Unix's inception in 1970 as a 2.5 thousand line kernel and 48 commands, to 2025 as a widely-used 41 million line system. The 2 GB repository contains about 850 thousand commits and more than eight thousand merges. Based on the repository's contents I provide details regarding the tape's contents, dating, code provenance, and the evolution of programming language adoption.
Attachments
Speakers
Diomidis Spinellis — @CoolSWEng.bsky.social or @CoolSWEng@mastodon.acm.org — is a Professor of Software Engineering in the Department of Management Science and Technology at the Athens University of Economics and Business, Greece, Professor of Software Analytics in the Department of Software Technology of the Delft University of Technology, and director of the Business Analytics Laboratory (BALab). His research interests include software engineering, IT security, and computing systems. He has written two award-winning, widely-translated books: Code Reading and Code Quality: The Open Source Perspective. His most recent book is Effective Debugging: 66 Specific Ways to Debug Software and Systems. Diomidis has also published more than 350 technical papers in journals and refereed conference proceedings, which have received more than 15000 citations. He served for two decades as a member of the IEEE Software editorial board, authoring the regular “Tools of the Trade” (2005–2014) and “Adeventures in Code” (2023 until now) columns, and as the magazine's Editor-in-Chief over the period 2015–2018. He has contributed code that ships with Apple’s macOS and BSD Unix and is the developer of the ai-cli-lib AI command-line copilot, git-issue, the Unix history repository, CScout, UMLGraph, dgsh, and other open-source software packages, libraries, and tools. In a previous life he was four times winner of the International Obfuscated C Code Contest. Nowadays he tries to keep his code boring.
Links
External Links
Notice: The placeholder video image is licensed under CC BY-SA 4.0. The original image can be found hereChanges made to the image are: Cropped the image to a new ratio, part of the image was cut off.