Concurrent DOS XM
| Developer | Digital Research, Inc. |
|---|---|
| OS family | CP/M |
| Working state | Current |
| Source model | Closed source |
| Latest release | 7.22 R18 / 2005-04-21 (REAL/32: 7.95) |
| Kernel type | Monolithic kernel |
| Default user interface | Command line interface |
| License | Proprietary |
| Official website | Various (see notes) |
Multiuser DOS is a real-time multi-user multi-tasking operating system for IBM PC-compatible microcomputers.
An evolution of the older Concurrent CP/M-86 and Concurrent DOS operating systems, it was originally developed by Digital Research and later acquired and further developed by Novell. Its ancestry lies in the earlier Digital Research 8-bit operating systems CP/M and MP/M, and the 16-bit single-tasking CP/M-86 which evolved from CP/M.
When Novell abandoned the system, the three Master Value Added Resellers (VARs) DataPac Australasia, Concurrent Controls and Intelligent Micro Software took over and continued independent development into Datapac Multiuser DOS and System Manager, CCI Multiuser DOS, and IMS Multiuser DOS and REAL/32.
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 commercially unsuccessful as IBM's PC DOS 1.0 offered much the same facilities for a considerably lower price. Like PC DOS, CP/M-86 did not 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 users using dumb terminals attached by serial ports. 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.
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