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| PC-MOS/386 | |
|---|---|
 A screen-print of the PC-MOS-386 startup screen | |
| Developer | The Software Link |
| Written in | 80x86assembly language,C |
| OS family | DOS |
| Working state | Active |
| Source model | Open source |
| Initial release | 1987; 38 years ago (1987) |
| Latest release | 5.01 |
| Repository | |
| Available in | English |
| Supported platforms | x86 architecture |
| Kernel type | Monolithic |
| Influenced by | MS-DOS |
| Default user interface | Command-line interface (COMMAND.COM) |
| License | GPL-3.0-only |
| Official website | Github |
PC-MOS/386 is amulti-user,multitaskingcomputer operating system produced byThe Software Link (TSL), announced atCOMDEX in November 1986 for February 1987 release.[1] PC-MOS/386, a successor to PC-MOS, can run manyMS-DOS programs on the host machine or aterminal connected to it. Unlike MS-DOS, PC-MOS/386 is optimized for theIntel 80386 processor; however early versions will run on anyx86 computer. PC-MOS/386 used to beproprietary, but it was released asopen-source software in 2017.[2][3]
The last commercial version produced was v5.01, compatible with MS-DOS 5. It required amemory management unit (MMU) to supportmemory protection, so was not compatible with earlier8086 and8088 processors.[citation needed] MMU support for286-class machines was provided using a proprietary hardwareshim 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 runningprocesses. Typically swapping from a foreground to abackground process on the same terminal used the keyboard to generate aninterrupt and then swap the processes. The cost ofRAM (over US$500/Mb in 1987) and the slow and expensive hard disks of the day limited performance.[citation needed]
PC-MOS used"dumb" terminals, referred to within MOS as 'workstations', connected to the machine running the operating system viaserial ports communicating at 9600, 19200 or 38400baud. Either dedicated terminals or computers runningterminal emulation 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 lawsuitArizona 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'sshrinkwrap licensing. 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 ayear 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 underGPL v3 and itssource code uploaded toGitHub,[2][3] with the "year 2012" issue corrected.[6]
Commands supported by PC-MOS Version 4 are:[4]
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