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UNIX V4 Tape Successfully Recovered: First Ever Version of UNIX Written in C is Running Again
**In a remarkable discovery, the contents of an over-half-a-century old tape have been successfully retrieved from a 1970s nine-track tape drive. The recovered files belong to UNIX V4, the first ever version of the UNIX operating system written in the then-new C programming language.
The recovery was made possible by Computer History Museum software curator Al Kossow, who imaged the tape using the readtape program developed by the museum's Len Shustek. The data was recovered from the raw magnetic flux variations on the tape, allowing for some error correction and reconstruction of the digital data.
The recovered UNIX V4 files are now available to download from the Internet Archive, and can be run in SimH, a software emulator that simulates classic computer systems. Angelo Papenhoff has also provided a processed version of the files, complete with a README file explaining how to run it.
For those interested in running UNIX V4, Reddit user drop_table_allusers provides step-by-step instructions on how to boot the system using SimH. The process involves starting the pdp-11 executable and passing the boot.ini file as a parameter, followed by typing 'unix' and pressing enter.
The recovered UNIX V4 codebase contains around 55,000 lines of code, with about 25,000 lines written in C. This is a significant milestone for the history of UNIX, which has been shrouded in mystery for decades. The recovery of UNIX V4 provides valuable insights into the development of UNIX and its evolution over time.
**A Brief History of UNIX**
UNIX was first developed by Ken Thompson and Dennis Ritchie at Bell Labs in the late 1960s. The first version, known as the "Zeroth edition", was hand-coded in assembly language for a PDP-7 minicomputer. This was followed by UNIX First Edition, which was rewritten for a PDP-11 machine.
UNIX V2 and V3 were developed later that year, introducing new features such as pipes. UNIX V4 marked the first time much of the kernel was rewritten in C, making it a significant evolutionary step in the development of the operating system.
**The Evolution of UNIX**
UNIX started out as a simple and tiny OS, written by two geniuses in their spare time to run a simulation game called Space Travel. The project was meant to be a quick hack, but it eventually escaped the lab and became widely adopted by industry and academia.
The original developers continued to work on UNIX, improving and refactoring it until the Tenth Edition. This was followed by Plan 9 from Bell Labs, which was radically rewritten to become a network-aware operating system.
**A Crucial Early Evolutionary Step**
The recovery of UNIX V4 is a significant milestone in the history of UNIX. It provides valuable insights into the development of the operating system and its evolution over time. The recovered files are now available for download, allowing researchers and historians to study the early versions of UNIX.
**A Christmas Miracle!**
As one commentator noted, the recovery of UNIX V4 is "almost as if it were a Christmas miracle!" Indeed, it's a remarkable discovery that sheds new light on the history of UNIX. We're grateful for the work of Al Kossow and the Computer History Museum in making this possible.