PC-MOS/386 is a

multi-user Multi-user software is computer software that allows access by multiple users of a computer. Time-sharing systems are multi-user systems. Most batch processing systems for mainframe computers may also be considered "multi-user", to avoid leavi ...

, multitasking computer operating system produced by

The Software Link The Software Link, Inc. (TSL) was a company in Norcross, Georgia, Norcross, Georgia (U.S. state), Georgia that developed software for personal computers from 1986 to 1994. The company was co-founded by Rod Roark and Gary Robertson. Products * PC ...

(TSL), announced at COMDEX in November 1986 for February 1987 release. PC-MOS/386, a successor to PC-MOS, can run many

MS-DOS MS-DOS ( ; acronym for Microsoft Disk Operating System, also known as Microsoft DOS) is an operating system for x86-based personal computers mostly developed by Microsoft. Collectively, MS-DOS, its rebranding as IBM PC DOS, and a few op ...

programs on the host machine or a terminal connected to it. Unlike MS-DOS, PC-MOS/386 is optimized for the

Intel 80386 The Intel 386, originally released as the 80386 and later renamed i386, is the third-generation x86 architecture microprocessor from Intel. It was the first 32-bit computing, 32-bit processor in the line, making it a significant evolution in ...

processor; however early versions will run on any

x86 x86 (also known as 80x86 or the 8086 family) is a family of complex instruction set computer (CISC) instruction set architectures initially developed by Intel, based on the 8086 microprocessor and its 8-bit-external-bus variant, the 8088. Th ...

computer. PC-MOS/386 used to be proprietary, but it was released as

open-source software Open-source software (OSS) is Software, computer software that is released under a Open-source license, license in which the copyright holder grants users the rights to use, study, change, and Software distribution, distribute the software an ...

in 2017.

History

The last commercial version produced was v5.01, compatible with MS-DOS 5. It required a

memory management unit A memory management unit (MMU), sometimes called paged memory management unit (PMMU), is a computer hardware unit that examines all references to computer memory, memory, and translates the memory addresses being referenced, known as virtual mem ...

(MMU) to support

memory protection Memory protection is a way to control memory access rights on a computer, and is a part of most modern instruction set architectures and operating systems. The main purpose of memory protection is to prevent a process from accessing memory that h ...

, so was not compatible with earlier

8086 The 8086 (also called iAPX 86) is a 16-bit microprocessor chip designed by Intel between early 1976 and June 8, 1978, when it was released. The Intel 8088, released July 1, 1979, is a slightly modified chip with an external 8-bit data bus (allo ...

and 8088 processors. MMU support for 286-class machines was provided using a proprietary hardware shim inserted between the processor and its socket. 386 machines did not require any special hardware. Multi-user operation suffered from the limitations of the day including the inability of the processor to schedule and partition running processes. Typically swapping from a foreground to a

background process A background process is a computer process that runs ''behind the scenes'' (i.e., in the background) and without user intervention. Typical tasks for these processes include logging, system monitoring, scheduling, and user notification. On a Wind ...

on the same terminal used the keyboard to generate an

interrupt In digital computers, an interrupt (sometimes referred to as a trap) is a request for the processor to ''interrupt'' currently executing code (when permitted), so that the event can be processed in a timely manner. If the request is accepted ...

and then swap the processes. The cost of RAM (over US$500/ Mb in 1987) and the slow and expensive hard disks of the day limited performance. PC-MOS used "dumb" terminals, referred to within MOS as 'workstations', connected to the machine running the operating system via

serial port A serial port is a serial communication Interface (computing), interface through which information transfers in or out sequentially one bit at a time. This is in contrast to a parallel port, which communicates multiple bits simultaneously in Pa ...

s communicating at 9600, 19200 or 38400 baud. Either dedicated terminals or computers running terminal emulation software could be used. All processing was done by the PC-MOS machine. 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. 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. The result of the case, which Arizona Retail Systems won, helped to establish US legal precedent regarding the enforceability of shrinkwrap licenses. There was a

year 2000 problem The term year 2000 problem, or simply Y2K, refers to potential computer errors related to the Time formatting and storage bugs, formatting and storage of calendar data for dates in and after the year 2000. Many Computer program, programs repr ...

-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. On 21 July 2017 PCMOS/386 was relicensed under GPL v3 and its

source code In computing, source code, or simply code or source, is a plain text computer program written in a programming language. A programmer writes the human readable source code to control the behavior of a computer. Since a computer, at base, only ...

uploaded to

GitHub GitHub () is a Proprietary software, proprietary developer platform that allows developers to create, store, manage, and share their code. It uses Git to provide distributed version control and GitHub itself provides access control, bug trackin ...

, with the "year 2012" issue corrected.

Commands

Commands supported by PC-MOS Version 4 are:

General commands

* ADDDEV * ALIAS * BREAK * CD * CLS *

COMMAND Command may refer to: Computing * Command (computing), a statement in a computer language * command (Unix), a Unix command * COMMAND.COM, the default operating system shell and command-line interpreter for DOS * Command key, a modifier key on A ...

* COMPFILE * COPY * DATE * DIR * DIRMAP * DISKCOPY * DISKID * DOT * ENVSIZE * ERASE * EXCEPT * EXPORT * FILEMODE * FORMAT *

HELP Help may refer to: Arts, entertainment, and media Films * Help (2010 film), ''Help'' (2010 film), a Bollywood horror film * Help (2021 theatrical film), ''Help'' (2021 theatrical film), a British psychological thriller film * Help (2021 TV ...

* IMPORT * MD * MORE * MSORT * MSYS * ONLY *

PATH A path is a route for physical travel – see Trail. Path or PATH may also refer to: Physical paths of different types * Bicycle path * Bridle path, used by people on horseback * Course (navigation), the intended path of a vehicle * Desir ...

* PROMPT * RD * REL * REMDEV * RENAME * SEARCH *

SET Set, The Set, SET or SETS may refer to: Science, technology, and mathematics Mathematics *Set (mathematics), a collection of elements *Category of sets, the category whose objects and morphisms are sets and total functions, respectively Electro ...

* SWITCH *

TIME Time is the continuous progression of existence that occurs in an apparently irreversible process, irreversible succession from the past, through the present, and into the future. It is a component quantity of various measurements used to sequ ...

TYPE Type may refer to: Science and technology Computing * Typing, producing text via a keyboard, typewriter, etc. * Data type, collection of values used for computations. * File type * TYPE (DOS command), a command to display contents of a file. * ...

VERIFY CONFIG.SYS is the primary configuration file for the DOS and OS/2 operating systems. It is a special ASCII text file that contains user-accessible setup or configuration directives evaluated by the operating system's DOS BIOS (typically residi ...

* WVER

Batch file commands

* ABORT * ADDTASK * AUTOCD * BATECHO *

CALL Call or Calls may refer to: Arts, entertainment, and media Games * Call (poker), a bet matching an opponent's * Call, in the game of contract bridge, a bid, pass, double, or redouble in the bidding stage Music and dance * Call (band), from L ...

RETURN Return may refer to: In business, economics, and finance * Return on investment (ROI), the financial gain after an expense. * Rate of return, the financial term for the profit or loss derived from an investment * Tax return, a blank document or t ...

* ECHO * FLUSH * FOR * GOTO * IF * INSERT * KEY * NEXT * PAUSE * REM * STOP * SWITCH * TEXT * ENDTEXT

Multitask/Multiuser commands

* ADDTASK * KEYMAP * MOS * MOSADM * REMTASK

Print spooler

* PRINT * SPOOL

Security commands

* CLASS * SIGNOFF * SIGNON

Installation, administration and debug commands

DEBUG In engineering, debugging is the process of finding the root cause, workarounds, and possible fixes for bugs. For software, debugging tactics can involve interactive debugging, control flow analysis, log file analysis, monitoring at the ap ...

* ED * HDSETUP

References

{{FOSS 1987 software Discontinued operating systems Disk operating systems DOS variants Formerly proprietary software Free software operating systems Assembly language software X86 operating systems