Editing Multiuser DOS (section)

=={{anchor|CCP/M-86}}Concurrent CP/M-86==
{{See also|MP/M#MP/M-86{{!}}MP/M-86}}
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The initial version of [[CP/M-86 1.0]] (with BDOS 2.x) was adapted and became available to the [[IBM PC]] in 1982.<!-- it was already available for non-PC platforms in 1981, possibly 1980. --> It was commercially unsuccessful as [[IBM]]'s [[PC&nbsp;DOS 1.0]] offered much the same facilities for a considerably lower price. Neither PC&nbsp;DOS nor CP/M-86 could fully exploit the power and capabilities of the new 16-bit machine.

It was soon supplemented by an implementation of CP/M's multitasking 'big brother', [[MP/M-86 2.0]], since September 1981. This turned a PC into a multiuser machine capable of supporting multiple [[concurrent user]]s 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 shared-data applications such as accounts or stock control in a time when PC networks were rare, very expensive and difficult to implement.

[[CP/M-86 1.1]] (with [[BDOS]] 2.2) and MP/M-86 2.1 were merged to create Concurrent CP/M-86 3.0 (also known as CCP/M-86) with BDOS 3.0 in late 1982.<ref name="Kildall_1982_8-bit"/> [[Kathryn Strutynski]], the project manager for CP/M-86, was also the project manager for Concurrent CP/M-86. One of its designers was Francis "Frank" R. Holsworth.<ref name="Wein_2002"/><ref name="Holsworth_2006"/> Initially, this was a single-user operating system supporting true multi-tasking of up to four (in its default configuration) CP/M-86 compatible programs. Like its predecessors it could be configured for [[multi-processor]] support (see e.g. Concurrent CP/M-86/80) and also added "virtual screens" letting an operator switch between multiple interacting programs.<ref name="Kildall_1982_8-bit"/> Later versions supported dumb terminals connected to the CP/M-86 machine as multiuser systems. Concurrent CP/M-86 3.1 (BDOS 3.1) shipped on 21 February 1984.<ref name="DRI_1984_CCPM31"/>

===Adaptations===

===={{anchor|CCP/M-86 with Windows}}Concurrent CP/M-86 with Windows====
In February 1984 Digital Research also offered a version of Concurrent CP/M-86 with windowing capabilities named '''Concurrent CP/M with Windows for the IBM Personal Computer and Personal Computer XT'''.<ref name="CCPM_1984"/>

===={{anchor|CCP/M-86/80}}Concurrent CP/M-86/80====
{{See also|CP/M-86/80|CP/M 8-16|MP/M 8-16}}
This was an adaptation of Concurrent CP/M-86 for the LSI-M4, LSI Octopus<ref name="LSI_Octopus"/> and CAL PC computers. These machines had both 16-bit and 8-bit processors, because in the early days of 16-bit personal computing, 8-bit software was more available and often ran faster than the corresponding 16-bit software. Concurrent CP/M-86/80 allowed users to run both CP/M (8-bit) and CP/M-86 (16-bit) applications. When a command was entered, the operating system ran the corresponding application on either the 8-bit or the 16-bit processor, depending on whether the executable file had a [[.COM (file extension)|.COM]] or [[CMD file (CP/M)|.CMD]] extension. It emulated a CP/M environment for 8-bit programs by translating CP/M [[system call]]s into CP/M-86 system calls, which were then executed by the 16-bit processor.<ref name="Kildall_1982_8-bit"/>