Multiuser DOS: differenze tra le versioni

Versione delle 00:12, 21 nov 2007

Versione delle 01:14, 21 nov 2007

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Evoluzione del più vecchi sistemi operativi '''Concurrent CP/M''' e '''Concurrent DOS''', venne sviluppato originariamente da [[Digital Research]], e discende direttamente dai precedenti [[CP/M]] ed [[MP/M]].

La prima versione di CP/M per il PC IBM, '''CP/M-86''', non fu un successo commerciale, dal momento che l'[[MS-DOS]] di [[Microsoft]] offriva più o meno le stesse possibilità ad un prezzo considerevolmente inferiore. In maniera del tutto simile ad MS-DOS 1.0, CP/M-86 non sfruttava appieno la potenza e le capacità del nuovo sistema a [[16 bit]]. Essa venne presto soppiantata da un implementazione del "fratello maggiore" del CP/M con supporto [[multitasking]], '''MP/M-86''', cosa che rese un PC un sistema multiutente in grado di gestire più accessi contemporaneamente attraverso [[Terminale (informatica)|terminali]] collegai alle porte seriali. L'ambiente presentato dava a ciascun utente l'impressione di avere il pieno controllo sul sistema.

Dal momento che i terminali costavano molto meno di un PC del tempo, essi offrivano risparmi considerevoli, e facilitavano l'utilizzo di applicazioni multiutente come quelli per il controllo di conti bancari o di azioni in un periodo in cui le reti di computer erano rare, molto costose e difficili da implementare.

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<!-- CP/M-86 and MP/M-86 were later merged to create Concurrent CP/M (also known as ''CCP/M''), which offered more complete CP/M-86 compatibility in addition to MP/M-86's multiuser capabilities.

The initial version of CP/M for the IBM PC, '''CP/M-86''', was commercially unsuccessful, as [[Microsoft]]'s [[MS-DOS]] offered much the same facilities for a considerably lower price. Like MS-DOS 1.0, CP/M-86 did not fully exploit the power and capabilities of the new [[16-bit]] machine.

It was soon superseded by an implementation of CP/M's multitasking 'big brother', '''MP/M-86'''. This turned a PC into a multiuser machine capable of supporting multiple concurrent users using [[dumb terminal]]s attached by [[serial port]]s. The environment presented to each user made it seem as if they had the entire computer to themselves. Since terminals cost a fraction of the then-substantial price of a complete PC, this offered considerable cost savings, as well as facilitating multi-user applications such as accounts or stock control in a time when PC networks were rare, very expensive and difficult to implement.

CP/M-86 and MP/M-86 were later merged to create Concurrent CP/M (also known as ''CCP/M''), which offered more complete CP/M-86 compatibility in addition to MP/M-86's multiuser capabilities.

As the origin of MS-DOS was as a clone of CP/M, this operating system also offered limited compatibility with MS-DOS - simple MS-DOS applications which did not directly access the screen or other hardware could be run under CCP/M. For example, although a console program such as [[PKZip]] worked perfectly and offered more facilities than the CP/M-native ''Arc'' archiver, more complex applications which performed screen manipulations, such as [[WordStar]] for DOS, would not and thus native CCP/M versions were required.

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MDOS was also unable to use many common MS-DOS additions such as network stacks, and it was limited in its ability to support later developments in the PC-compatible world, such as graphics adaptors, sound cards, CD-ROM drives and mice. Although many of these were soon rectified - for example, graphical terminals were developed, allowing users to use [[Color_Graphics_Adapter|CGA]], [[Enhanced_Graphics_Adapter|EGA]] and [[VGA]] software - it was less flexible in this regard than a network of individual PCs, and as the prices of these fell, it became less and less competitive, although it still offered benefits in terms of management and TCO (total cost of ownership.) Unlike MP/M, it never became popular as a multitasking OS for single users, partly because of license costs and partly because of the requirement for special device drivers - unlike multitasking DOS additions such as Quarterdeck's [[DESQview]].

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==See also==

[[Categoria:Sistemi operativi real-time]]

* [[CP/M]]

[[CategoryCategoria:Digital Research]]

* [[MP/M]]

* [[DR-DOS]]

* [[OpenDOS]]

* [[PC-MOS/386]]

* [[FreeDOS]]

==External links==

* [http://www.lesbell.com.au/Home.nsf/web/CP%2FM+and+Derivatives?OpenDocument History of CP/M, CCP/M and CDOS development]

* [http://www.conctrls.com/ Concurrent Controls - vendors of Multiuser DOS]

* [http://www.imsltd.com/ IMS Ltd - vendors of Multiuser DOS derivative Real/32]

[[Category:DOS on IBM PC compatibles]]

[[Category:Digital Research]]

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