CP/M (Control Program for Microcomputers)

🧩 1. Basic Information

Field —>Description
OS Name —>CP/M (Control Program for Microcomputers)
Developer —>Digital Research, Inc. (Gary Kildall)
First Released —>1974 (initial internal), 1976 (commercial)
Latest Version —>CP/M-86 (1982+), CP/M-Plus (3.0)
License Type —>Originally proprietary, later open-sourced as historic software
Supported Platforms —>Intel 8080 / Zilog Z80 (8-bit), later Intel 8086 (16-bit)
Still Active? —>❌ No (historic; preserved by hobbyists & emulators)

⚙️ 2. Kernel & Architecture

Kernel Type: Simple monolithic command monitor & BIOS layer

Based On: Designed for Intel 8080 & compatible 8-bit microcomputers

Architecture Support:

Memory Model: Flat address space, typically ~64 KB maximum

BIOS/BDOS split: BDOS handles disk & file I/O, BIOS handles hardware-specific routines

🌟 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

📈 4. Version History & Important Milestones ✅

Version / Milestone —>Year —>Description
CP/M 1.0 —>1974 —>First internal version, ran on Intel 8080
CP/M 2.2 —>1979 —>Most popular version, mass adoption on S-100 & home computers
CP/M-86 —>1981 —>Port to Intel 8086/8088, competed with MS-DOS
CP/M-Plus (3.0) —>Early 80s —>Added bank switching, better memory handling
Lost IBM PC deal —>~1980 —>Missed chance to become default PC OS; IBM chose MS-DOS
Source released historic —>2001± –>Gary Kildall’s family & Caldera released CP/M source for public preservation

🎯 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

✅ 6. Pros & Cons

Pros —>Cons
Created first real standard OS for microcomputers —>Limited to simple single-task workflows
Portable across dozens of hardware types —>No built-in multitasking or memory protection
Huge software library for its time —>Needed manual disk swaps, low-level error handling
Simple architecture easy to learn —>Quickly outpaced by MS-DOS on PCs

🎨 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: “Insert Disk B and press RETURN”

Emulator demos (like MYZ80 or SIMH) showing old software running on CP/M

📦 8. Ecosystem & App Support

Popular applications:

Thousands of utilities & tools — the first true microcomputer software ecosystem

CP/M format disks became a standard for file exchange

🔐 9. Security & Updates

No concept of multi-user security or file permissions — trusted single-user environments

System updates typically distributed on floppy disks by vendors

Reliability depended on careful use & manually backing up floppy disks

🌍 10. Community, License & Development

License: Originally proprietary by Digital Research, now released for preservation

Massive hobbyist communities in the 70s–80s — 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 — directly influenced MS-DOS (similar commands, file systems)