PhysTechSoft was formed in 1991 in Moscow, Russia by graduates and members of MIPT, informally known as PhysTech. At the end of 1993, PhysTechSoft released the first commercially available PTS-DOS as PTS-DOS v6.4. The version numbering followed MS-DOS version numbers, as Microsoft released MS-DOS 6.2 in November 1993.
In 1995, some programmers left PhysTechSoft and founded Paragon Software Group. They took source code with them and released their own version named PTS-DOS v6.51CD. According to official PhysTechSoft announcements, these programmers violated both copyright laws and Russian military laws, as PTS-DOS was developed in close relationship with Russia's military and thus may be subject to military secrets law.
PhysTechSoft continued development on their own and released PTS-DOS v6.6 somewhere between and presented PTS-DOS v6.65 at the CeBIT exhibition in 1997. The next version from PhysTechSoft, formally PTS/DOS Extended Version 6.70 was labeled PTS-DOS 2000 and is still being distributed as a last 16-bit PTS-DOS system, as of 2007[update].
Paragon continued their PTS-DOS line and released Paragon DOS Pro 2000 (also known and labeled in some places as PTS/DOS Pro 2000). According to Paragon, this was the last version and all development since then ceased. Moreover, this release contained bundled source code of older PTS-DOS v6.51.
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