CP/M (Control Program for Microcomputers)

TL;DR
Control Program for Microcomputers Simple monolithic command monitor & BIOS layer Designed for Intel 8080 & compatible 8-bit microcomputers
π§© 1. Basic Information
Field                                                       β>Description
OS Name                                              β>CP/M (Control Program for Microcomputers)
Developer                                           β>Digital Research, Inc. (Gary Kildall)
First Released                                   β>1974 (initial internal), 1976 (commercial)
Latest Version                                 β>CP/M-86 (1982+), CP/M-Plus (3.0)
License Type                                   β>Originally proprietary, later open-sourced as historic software
Supported Platforms                   β>Intel 8080 / Zilog Z80 (8-bit), later Intel 8086 (16-bit)
Still Active?                                     β>β No (historic; preserved by hobbyists & emulators)
βοΈ 2. Kernel & Architecture
Kernel Type: Simple monolithic command monitor & BIOS layer
Based On: Designed for Intel 8080 & compatible 8-bit microcomputers
Architecture Support:
Original: 8-bit systems (8080, 8085, Z80)
Later: CP/M-86 for 16-bit Intel 8086/8088
Memory Model: Flat address space, typically ~64 KB maximum
BIOS/BDOS split: BDOS handles disk & file I/O, BIOS handles hardware-specific routines
π 3. Key Features
Provided a standard OS interface across wildly different microcomputers
Command-line driven interface (A>, B>)
Standardized file system (8.3 filenames, flat directory)
Portable applications across CP/M machines (WordStar, dBase II, SuperCalc)
Modular BIOS layer allowed hardware makers to adapt CP/M to new machines
π 4. Version History & Important Milestones β
  Version / Milestone                   β>Year                           β>Description
CP/M 1.0                                  β>1974         β>First internal version, ran on Intel 8080
CP/M 2.2                                  β>1979        β>Most popular version, mass adoption on S-100 & home                                                                                  computers
CP/M-86                                 β>1981         β>Port to Intel 8086/8088, competed with MS-DOS
CP/M-Plus (3.0)                     β>Early 80s  β>Added bank switching, better memory handling
Lost IBM PC deal                   β>~1980       β>Missed chance to become default PC OS; IBM chose                                                                                      MS-DOS
Source released historic       β>2001Β±         β>Gary Kildallβs family & Caldera released CP/M source for                                                                                public preservation
π― 5. Target Audience & Use Cases
Hobbyists & early computer enthusiasts: Build-your-own S-100 bus machines
Small businesses: Running word processors, spreadsheets, databases
Developers: Writing portable assembly & C programs across multiple vendors
Educational use: Teaching early microprocessor programming & OS concepts
β 6. Pros & Cons
                                        Pros                                                                                β>Cons
Created first real standard OS for microcomputers       β>Limited to simple single-task workflows
Portable across dozens of hardware types                    β>No built-in multitasking or memory protection
Huge software library for its time                                    β>Needed manual disk swaps, low-level error                                                                                                     handling
Simple architecture easy to learn                                   β>Quickly outpaced by MS-DOS on PCs
π¨ 7. UI Demo & Visuals
Typical CP/M command prompt:
css
CopyEdit
A>_
Commands like DIR, PIP, STAT, ED
Running WordStar word processor or SuperCalc spreadsheet
Disk change prompts: βInsert Disk B and press RETURNβ
Emulator demos (like MYZ80 or SIMH) showing old software running on CP/M
π¦ 8. Ecosystem & App Support
Popular applications:
WordStar (word processing)
dBase II (database)
SuperCalc (spreadsheet)
Turbo Pascal compiler
Thousands of utilities & tools β the first true microcomputer software ecosystem
CP/M format disks became a standard for file exchange
π 9. Security & Updates
No concept of multi-user security or file permissions β trusted single-user environments
System updates typically distributed on floppy disks by vendors
Reliability depended on careful use & manually backing up floppy disks
π 10. Community, License & Development
License: Originally proprietary by Digital Research, now released for preservation
Massive hobbyist communities in the 70sβ80s β local computer clubs, BBS sharing CP/M software
Today kept alive via emulators like CP/M-86 under DOSBox, SIMH, MYZ80
Important piece of computing history β directly influenced MS-DOS (similar commands, file systems)
