Ancient UNIX

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Version 5 Unix for the PDP-11, running on SIMH
Version 6 Unix for the PDP-11, running in SIMH
Version 7 Unix for the PDP-11, running in SIMH

Ancient UNIX is any early release of the Unix code base prior to Unix System III, particularly the Research Unix releases prior to and including Version 7 (the base for UNIX/32V as well as later developments of AT&T Unix).

After the publication of the Lions' book, work was undertaken to release earlier versions of the codebase. SCO first released the code under a limited educational license.[citation needed]

Later, in January 2002, Caldera International (now SCO Group) relicensed (but has not made available) several versions under the four-clause BSD license, namely:[1][2]

As of 2022, there has been no widespread use of the code, but it can be used on emulator systems, and Version 5 Unix runs on the Nintendo Game Boy Advance using the SIMH PDP-11 emulator.[3] Version 6 Unix provides the basis for the MIT xv6 teaching system, which is an update of that version to ANSI C and the x86 or RISC-V platform.

The BSD vi text editor is based on code from the ed line editor in those early Unixes. Therefore, "traditional" vi could not be distributed freely, and various work-alikes (such as nvi) were created. Now that the original code is no longer encumbered, the "traditional" vi has been adapted for modern Unix-like operating systems.[4]

SCO Group, Inc. was previously called Caldera International. As a result of the SCO Group, Inc. v. Novell, Inc. case, Novell, Inc. was found to not have transferred the copyrights of UNIX to SCO Group, Inc.[5] Concerns have been raised regarding the validity of the Caldera license.[6][7]

The Unix Heritage Society[edit]

The Unix Heritage Society was founded by Warren Toomey.[8][9][10][11][12][13][14][excessive citations] First edition Unix was restored to a usable state by a restoration team from the Unix Heritage Society in 2008. The restoration process started with paper listings of the source code which were in Unix PDP-11 assembly language.[15][16]


  1. ^ Johnson II, Dion L. (2002-01-24). "Liberal license for ancient UNIX sources".
  2. ^ Broderick, Bill (January 23, 2002). "Dear Unix enthusiasts" (PDF). Caldera International. Archived from the original (PDF) on February 19, 2009.
  3. ^ Singh, Amit (August 2004). "UNIX® on the Game Boy Advance". Archived from the original on 2006-08-31. Retrieved 2009-10-22.
  4. ^ "The Traditional Vi".
  5. ^ "10th Circuit Court of Appeals Decision" (PDF).
  6. ^ Warren Toomey. "The Push to Get Free Unix Licenses".
  7. ^ "Why BSD/OS is the best candidate for being the only tested legally open UNIX".
  8. ^ "Interview with Warren Toomey, Founder of the Unix Heritage Society". USENIX. 13 January 2023. Retrieved 15 June 2023.
  9. ^ Davis, A. Jesse Jiryu (June 14, 2017). "Assembling the history of Unix". Retrieved 15 June 2023.
  10. ^ Jude, Allan (October 13, 2022). "Warren Toomey interview". BSD Now. Retrieved 15 June 2023. MP3 44:34
  11. ^ Chirgwin, Richard. "Samizdat no more: Old Unix source code opened for study". Retrieved 15 June 2023.
  12. ^ "Warren Toomey : contributions". Retrieved 15 June 2023.
  13. ^ "SCO may not know origin of code, says Australian UNIX historian". The Sydney Morning Herald. 9 September 2003. Retrieved 15 June 2023.
  14. ^ Toomey, Warren (2010). "First Edition Unix: Its Creation and Restoration". IEEE Annals of the History of Computing. 32 (3): 74–82. ISSN 1934-1547. Retrieved 15 June 2023.
  15. ^ Toomey, Warren (July 2010). "First Edition Unix: Its Creation and Restoration". IEEE Annals of the History of Computing. 32 (3): 74–82. doi:10.1109/MAHC.2009.55. S2CID 18586380.
  16. ^ The Restoration of Early UNIX Artifacts

External links[edit]