CP/NET

MP/M
Company type	Operating system
Industry	Computer software
Founded	1979
Founder	Tom Rolander
Products	MP/M-80, MP/M-86, MP/M 8-16, MP/M-286
Parent	Digital Research

MP/M (short for Multi-Programming Monitor Control Program) was a multi-user iteration of the CP/M operating system, created by Digital Research's Tom Rolander in 1979. It allowed several users to access a single computer simultaneously through individual terminals.

For microcomputers of its era, MP/M was notably sophisticated, incorporating a priority-based multitasking kernel—referred to as the nucleus—that included memory protection, simultaneous input/output processing (XIOS), and capabilities for spooling and task queue management. This enabled users to execute multiple applications concurrently and switch between them seamlessly.

MP/M-80

Designed for 8-bit processors such as the Intel 8080 or Zilog Z80, MP/M-80 required a minimum of 32 KB RAM, which restricted application memory availability. To overcome this limitation, MP/M employed bank switching—loading programs into RAM banks outside the CPU's direct addressable range and swapping them into lower memory as needed. This approach was subsequently incorporated into CP/M version 3.0.

Unexpectedly, MP/M gained traction among "power users" as a single-user operating system due to its multitasking capabilities and enhanced memory management.

The release of MP/M II 2.0 in 1981 introduced file sharing functionality, followed by MP/M II 2.1 in January 1982, which added advanced file locking mechanisms.

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; added enhanced file locking)

MP/M-86

Mirroring CP/M’s evolution, MP/M was adapted for the 16-bit Intel 8086 processor and launched as MP/M-86 2.0 in September 1981. Among the principal contributors was Francis "Frank" R. Holsworth, who later became Digital Research’s marketing director. Known releases include MP/M-86 2.0 in late 1981 and MP/M-86 2.1 in July 1982.

The 2.1 version incorporated elements from CP/M-86 1.1 (BDOS 2.2), resulting in Concurrent CP/M-86 version 3.0 (BDOS 3.0) by the end of 1982, which introduced features such as "virtual screens". Project manager Kathryn Strutynski continued guiding this progression. In December 1983, an optional DOS emulator named PC-MODE was unveiled for Concurrent CP/M-86 3.1 (BDOS 3.1), shipping by February 1984. This platform further evolved into the MS-DOS compatible Concurrent DOS (BDOS versions beyond 3.1), eventually leading to FlexOS and Multiuser DOS, systems still utilized within select industrial environments.

The term CCP/M is commonly used as an abbreviation for Concurrent CP/M.

MP/M 8-16

The designation MP/M 8-16 (also known as MP/M-8/16) was used by CompuPro for a hybrid setup combining multi-user, multitasking capabilities of the 16-bit MP/M-86 for single-user CP/M operations alongside multi-user, multitasking support on the 8-bit MP/M running on the multi-processor CompuPro System 816 hardware platform. This system later accommodated Concurrent DOS 3.1.

MP/M-286

In 1982, Digital Research announced plans for MP/M-286, aiming to exploit the Intel 80286 processor’s advanced memory management and protection features while maintaining compatibility with existing MP/M-86 and CP/M-86 software. Although the original MP/M-286 release did not materialize as intended, it transformed into Concurrent CP/M-286, which served as a foundation for subsequent products such as Concurrent DOS 286 (1985) and FlexOS 286 (1986).

Commands

The Console Command Processor (CCP) for MP/M II provides support for the following instructions:

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 networking solution designed to link an MP/M server with multiple CP/NET clients operating under CP/M, a system originally developed by Tom Rolander.

CP/NET enhanced MP/M by incorporating networking capabilities, allowing the system to function both as a server and a requester in coordination with CP/M clients.

Diskless client setups were marketed as CP/NOS and MP/NOS; these configurations operated without local storage, instead relying on network access for resources.

These platforms supported shared file and printer access as well as electronic mail services.

Additional modules included:

NIOS – Network I/O System
SNIOS – Slave Network I/O System
NDOS – Network Disk Operating System

Versions of CP/NET ranged from 1.0 through 1.2 for the 8080 and Z80 processors, while CP/NET-86 was developed for the 8086 processor.

Subsequent products that followed were DR Net and FlexNet.

Legacy

Starting in 1997, Caldera granted permission for redistribution and modification of the original Digital Research CP/M and MP/M source code via Tim Olmstead's "The Unofficial CP/M Web site." Following Olmstead's death in 2001, Lineo, which acquired these assets afterward, broadened the free distribution license later that year to encourage continued community-driven development.

Notes