# PC-MOS/386 > Mediated Wiki article. Canonical URL: https://mediated.wiki/source/PC-MOS/386 > Markdown URL: https://mediated.wiki/source/PC-MOS/386.md > Source: https://en.wikipedia.org/wiki/PC-MOS%2F386 > Source revision: 1334538970 > License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) **PC-MOS/386** is a [multi-user](/source/Multi-user), [multitasking](/source/Computer_multitasking) [computer operating system](/source/Computer_operating_system) produced by [The Software Link](/source/The_Software_Link) (TSL), announced at [COMDEX](/source/COMDEX) in November 1986 for February 1987 release.[1] PC-MOS/386, a successor to PC-MOS, can run many [MS-DOS](/source/MS-DOS) programs on the host machine or a [terminal](/source/Computer_terminal) connected to it. Unlike MS-DOS, PC-MOS/386 is optimized for the [Intel 80386](/source/I386) processor; however early versions will run on any [x86](/source/X86) computer. PC-MOS/386 used to be [proprietary](/source/Proprietary_software), but it was released as [open-source software](/source/Open-source_software) in 2017.[2][3] ## History The last commercial version produced was v5.01, compatible with MS-DOS 5. It required a [memory management unit](/source/Memory_management_unit) (MMU) to support [memory protection](/source/Memory_protection), so was not compatible with earlier [8086](/source/Intel_8086) and [8088](/source/Intel_8088) processors.[citation needed] MMU support for [286](/source/Intel_80286)-class machines was provided using a proprietary hardware [shim](/source/Shim_(computing)) inserted between the processor and its socket. 386 machines did not require any special hardware.[4] Multi-user operation suffered from the limitations of the day including the inability of the processor to schedule and partition running [processes](/source/Process_(computing)). Typically swapping from a foreground to a [background process](/source/Background_process) on the same terminal used the keyboard to generate an [interrupt](/source/Hardware_interrupt) and then swap the processes. The cost of [RAM](/source/Random-access_memory) (over US$500/[Mb](/source/Megabyte) in 1987) and the slow and expensive hard disks of the day limited performance.[citation needed] PC-MOS used ["dumb" terminals](/source/Dumb_terminal), referred to within MOS as 'workstations', connected to the machine running the operating system via [serial ports](/source/Serial_port) communicating at 9600, 19200 or 38400 [baud](/source/Baud). Either dedicated terminals or computers running [terminal emulation](/source/Terminal_emulator) software could be used. All processing was done by the PC-MOS machine.[4] Terminals running at higher speeds required specialized hardware boards which increased cost, but the speed was not a serious limitation for interacting with the text-based programs predominantly used under MS-DOS.[citation needed] PC-MOS figured prominently in the lawsuit *Arizona Retail Systems, Inc. v. The Software Link, Inc.*, where Arizona Retail Systems claimed The Software Link violated implied warranties on PC-MOS. The case is notable because The Software Link argued that it had disclaimed the implied warranties via a license agreement on the software's [shrinkwrap licensing](/source/Shrinkwrap_(contract_law)). The result of the case, which Arizona Retail Systems won, helped to establish US legal precedent regarding the enforceability of shrinkwrap licenses.[5] There was a [year 2000 problem](/source/Year_2000_problem)-like error in this operating system, first manifesting on 1 August 2012 rather than 1 January 2000; files created on the system after this date would no longer work.[6] On 21 July 2017 PCMOS/386 was relicensed under [GPL v3](/source/GPL_v3) and its [source code](/source/Source_code) uploaded to [GitHub](/source/GitHub),[2][3] with the "year 2012" issue corrected.[6] ## Commands [Commands](/source/Command_(computing)) supported by PC-MOS Version 4 are:[4] ### General commands - ADDDEV - ALIAS - [BREAK](/source/BREAK_(DOS_command)) - [CD](/source/Cd_(command)) - [CLS](/source/CLS_(command)) - [COMMAND](/source/COMMAND.COM) - COMPFILE - [COPY](/source/Copy_(command)) - [DATE](/source/Date_(command)) - [DIR](/source/Dir_(command)) - DIRMAP - [DISKCOPY](/source/Diskcopy) - DISKID - DOT - ENVSIZE - [ERASE](/source/Del_(command)) - EXCEPT - EXPORT - FILEMODE - [FORMAT](/source/Format_(command)) - [HELP](/source/Help_(command)) - IMPORT - [MD](/source/Mkdir) - [MORE](/source/More_(command)) - MSORT - MSYS - ONLY - [PATH](/source/PATH_(DOS_command)) - [PROMPT](/source/PROMPT_(DOS_command)) - [RD](/source/Rmdir) - REL - REMDEV - [RENAME](/source/Ren_(command)) - SEARCH - [SET](/source/SET_(DOS_command)) - SWITCH - [TIME](/source/TIME_(command)) - [TYPE](/source/TYPE_(DOS_command)) - [VERIFY](/source/VERIFY_(DOS_command)) - WVER ### Batch file commands - ABORT - ADDTASK - AUTOCD - BATECHO - [CALL](/source/CALL_(DOS_command)) - [RETURN](/source/RETURN_(DOS_command)) - [ECHO](/source/Echo_(command)) - FLUSH - [FOR](/source/For_loop) - [GOTO](/source/Goto) - [IF](/source/IF_(DOS_command)) - INSERT - KEY - NEXT - [PAUSE](/source/PAUSE_(DOS_command)) - [REM](/source/Comment_(computer_programming)) - STOP - SWITCH - TEXT - ENDTEXT ### Multitask/Multiuser commands - ADDTASK - KEYMAP - MOS - MOSADM - REMTASK ### Print spooler - [PRINT](/source/PRINT_(command)) - SPOOL ### Security commands - CLASS - SIGNOFF - SIGNON ### Installation, administration and debug commands - [DEBUG](/source/Debug_(command)) - ED - HDSETUP ## See also - [DoubleDOS](/source/DoubleDOS) - [Multiuser DOS](/source/Multiuser_DOS) - Digital Research's unrelated multi-user operating system - [VM/386](/source/VM/386) - unrelated multi-tasking DOS environment - [Virtual DOS machine](/source/Virtual_DOS_machine) - [Multiuser DOS Federation](/source/Multiuser_DOS_Federation) - [FreeDOS](/source/FreeDOS) - [Timeline of operating systems](/source/Timeline_of_operating_systems) ## References 1. Lach, Eric (November 17, 1986). ["Multiuser Operating System to Use 386 Microprocessor's Virtual Modes"](https://books.google.com/books?id=izwEAAAAMBAJ&pg=PA15). *[InfoWorld](/source/InfoWorld)*. Vol. 8, no. 46. [Popular Computing, Inc.](/source/Computerworld). p. 15. [ISSN 0199-6649](https://www.worldcat.org/issn/0199-6649). Retrieved 1 May 2025. 1. Jansen, Roeland (8 February 2018). ["pcmos386v501: PC-MOS/386 v5.01 final release including cdrom driver sources"](https://github.com/roelandjansen/pcmos386v501). – via GitHub. 1. Vaughan-Nichols, Steven (23 October 2017). ["MS-DOS variant PC-MOS/386 reborn as open source"](https://www.zdnet.com/article/ms-dos-variant-pc-mos386-reborn-as-open-source/). *[ZDNET](/source/ZDNET)*. Retrieved 1 May 2025. 1. [*PC-MOS User Guide*](https://github.com/roelandjansen/pcmos386v501/blob/master/DOCS/v4/PCMOSv4UserManual.pdf). PC-MOS. 1991. pp. 23; 25; 31; 101–190; 207; 265–296. 1. ["cyber.harvard.edu/property00/alternatives/arizona.html"](https://cyber.harvard.edu/property00/alternatives/arizona.html). July 27, 1993. 1. Sprinkle, James (30 January 2019). ["files created after 20120731 seem to fail acc. wiki"](https://github.com/roelandjansen/pcmos386v501/issues/2#issuecomment-459088430). Retrieved 1 May 2025. – via [GitHub](/source/GitHub) --- Adapted from the Wikipedia article [PC-MOS/386](https://en.wikipedia.org/wiki/PC-MOS%2F386) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/PC-MOS%2F386?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.