CP/NOS
| Company type | Operating system |
|---|---|
| Industry | Software |
| Founded | 1979 |
| Founder | Tom Rolander |
| Products | MP/M, MP/M-80, MP/M-86, MP/M-286, MP/M II |
| Parent | Digital Research |
MP/M (short for Multi-Programming Monitor Control Program) was a multi-user adaptation of the CP/M operating system, created by Tom Rolander at Digital Research in 1979. This system allowed several users to access a single computer simultaneously through individual terminals.
At the time, MP/M was notably sophisticated for microcomputer environments, incorporating a priority-based multitasking kernel—referred to as the nucleus—with features such as memory protection, simultaneous input/output handling (XIOS), and capabilities for spooling and job queue management. It enabled users to execute and alternate between multiple applications concurrently.
MP/M-80
The 8-bit variant operated on an Intel 8080 or Zilog Z80 processor and required a minimum of 32 KB RAM, which constrained the memory available for programs. To address this limitation, MP/M implemented bank switching, a method that loaded software into RAM segments inaccessible directly by the CPU and swapped them into lower memory areas when necessary. This approach was later incorporated into CP/M version 3.0.
Interestingly, MP/M gained traction as an enhanced "power user" edition of CP/M tailored for individual users, providing multitasking and expanded memory addressing that justified its premium cost.
The MP/M II 2.0 release in 1981 introduced file sharing capabilities, followed by MP/M II 2.1 in January 1982, which added advanced file locking features.
Versions released include:
- MP/M 1.0 (1979)
- MP/M 1.1 (January 1980)
- MP/M II 2.0 (July 1981; introduced file sharing)
- MP/M II 2.1 (January 1982; enhanced file locking)
MP/M-86
Mirroring CP/M's evolution, MP/M was adapted for the 16-bit Intel 8086 processor as MP/M-86 2.0 in September 1981. Among its principal developers was Francis "Frank" R. Holsworth, who later served as Digital Research’s marketing director. Early revisions of MP/M-86 2.0 surfaced in late 1981, succeeded by MP/M-86 2.1 in July 1982.
By late 1982, MP/M-86 2.1 merged technologies from CP/M-86 1.1 (BDOS 2.2) to form Concurrent CP/M-86 version 3.0 (BDOS 3.0), which introduced enhancements such as "virtual screens." Development continued under project manager Kathryn Strutynski’s leadership. In December 1983, an optional DOS emulator named PC-MODE was launched for Concurrent CP/M-86 3.1 (BDOS 3.1), released in February 1984. This platform evolved further into the MS-DOS compatible Concurrent DOS, eventually leading to FlexOS and Multiuser DOS, systems still operational within certain industrial applications.
The name CCP/M is commonly used as an abbreviation for Concurrent CP/M.
MP/M 8-16
MP/M 8-16 (also known as MP/M-8/16) was CompuPro’s designation for a hybrid system combining the multi-user capabilities of the 16-bit MP/M-86 with single-user CP/M functionality alongside the multi-tasking, multi-user features of the 8-bit MP/M on the multi-processor CompuPro System 816 platform. This setup later supported Concurrent DOS 3.1.
MP/M-286
In 1982, Digital Research announced MP/M-286, designed to exploit the Intel 80286 processor’s advanced memory management and protection mechanisms for use with MP/M-86 and CP/M-86 software. Although this version did not launch as initially planned, it ultimately developed into Concurrent CP/M-286, which became the basis for Concurrent DOS 286 (released in 1985) and FlexOS 286 (introduced in 1986).
Commands
The Console Command Processor (CCP) within MP/M II offers support for the following set of commands:
- ABORT
- ATTACH
- ASM
- CONSOLE
- DDT
- DIR
- DSKRESET
- DUMP
- ED
- ERA
- ERAQ
- GENHEX
- GENMOD
- GENSYS
- LIB
- LINK
- LOAD
- MPMLDR
- MPMSTAT
- PIP
- PRINTER
- PRLCOM
- RDT
- REN
- RMAC
- SCHED
- SDIR
- SET
- SHOW
- SPOOL
- STAT
- STOPSPL
- SUBMIT
- TOD
- TYPE
- USER
- XREF
CP/NET, CP/NOS, MP/NET and MP/NOS
During the early 1980s, Digital Research introduced CP/NET, a network system designed to link an MP/M server with several CP/NET clients running the CP/M operating system, originally developed by Tom Rolander.
Building on MP/M, MP/NET incorporated networking capabilities allowing machines to function simultaneously as servers and requesters alongside CP/M client systems.
Versions for diskless clients featured the OS embedded in ROM: CP/NOS (Network Operating System) tailored for CP/M, and MP/NOS for MP/M, both dependent on network services to perform disk operations.
These platforms supported shared access to files and printers as well as electronic mail communication.
Associated components included:
- NIOS – Network Input/Output System
- SNIOS – Slave Network Input/Output System
- NDOS – Network Disk Operating System
CP/NET was released in multiple editions—1.0, 1.1, and 1.2—targeting 8080 and Z80 processors, alongside CP/NET-86 for the 8086 processor family.
Subsequent networking technologies evolved into DR Net and FlexNet.
Legacy
Beginning in 1997, Caldera granted permissions for redistribution and modification of original Digital Research software files, including source code for CP/M and MP/M, through Tim Olmstead's "The Unofficial CP/M Web site." Following Olmstead's passing in 2001, Lineo—the rights holder of Digital Research's assets—renewed and broadened this free distribution license, fostering ongoing community involvement and preservation efforts for these historic operating systems.