Retro System Rescue

Rescuing technology from the trash

CP/M Boot Disk


CP/M boot 5 1/4″ disks for various systems (either 2.2, 80 or 3.0 depending on the system).

Each disk is a new copy created from a disk image and has been verified to contain all the files required. As we do not have many of these systems we are not able to test that they will boot the original hardware but there should be no reason why that they will not work.

You can also find them listed on eBay

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From the CP/M Wikipedia entry (here)

The beginning and CP/M’s heyday

Gary Kildall originally developed CP/M during 1973-74, as an operating system to run on an Intel Intellec-8 development system, equipped with a Shugart Associates 8-inch floppy disk drive interfaced via a custom floppy disk controller.[10] It was written in Kildall’s own PL/M (Programming Language for Microcomputers).[9] Various aspects of CP/M were influenced by the TOPS-10 operating system of the DECsystem-10 mainframe computer, which Kildall had used as a development environment.

The name

CP/M originally stood for “Control Program/Monitor”. However, during the conversion of CP/M to a commercial product, trademark registration documents filed in November 1977 gave the product’s name as “Control Program for Microcomputers”[citation needed]. The CP/M name follows a prevailing naming scheme of the time, as in Kildall’s PL/M language, and Prime Computer’s PL/P (Programming Language for Prime), both suggesting IBM’s PL/I; and IBM’s CP/CMS operating system, which Kildall had used when working at the Naval Postgraduate School.

This renaming of CP/M was part of a larger effort by Kildall and his wife/business partner to convert Kildall’s personal project of CP/M and the Intel-contracted PL/M compiler into a commercial enterprise. The Kildalls astutely intended to establish the Digital Research brand and its product lines as synonymous with “microcomputer” in the consumer’s mind, similar to what IBM and Microsoft together later successfully accomplished in making “personal computer” synonymous with IBM and Microsoft product offerings. Intergalactic Digital Research, Inc. was later renamed via a corporation change-of-name filing to Digital Research, Inc.


Companies chose to support CP/M because of its large library of software. The Xerox 820 ran it because “where there are literally thousands of programs written for it, it would be unwise not to take advantage of it”, Xerox said. By 1984 Columbia University used the same source code to build Kermit binaries for more than a dozen different CP/M systems, plus a generic version. The operating system was described as a “software bus”, allowing multiple programs to interact with different hardware in a standardized way. Programs written for CP/M were typically portable among different machines, usually requiring only the specification of the escape sequences for control of the screen and printer. This portability made CP/M popular, and much more software was written for CP/M than for operating systems that ran on only one brand of hardware. One restriction on portability was that certain programs used the extended instruction set of the Z80 processor and would not operate on an 8080 or 8085 processor.

Bill Gates claimed that the Apple II family with a Z-80 SoftCard was the single most-popular CP/M hardware platform. Many different brands of machines ran the operating system, some notable examples being the Altair 8800, the IMSAI 8080, the Osborne 1 and Kaypro luggables, and MSX computers. The best-selling CP/M-capable system of all time was probably the Amstrad PCW. In the UK, CP/M was also available on Research Machines educational computers (with the CP/M source code published as an educational resource), and for the BBC Micro when equipped with a Z80 co-processor. Furthermore, it was available for the Amstrad CPC series, the Commodore 128, TRS-80, and later models of the ZX Spectrum.


WordStar, one of the first widely used word processors, and dBASE, an early and popular database program for small computers, were originally written for CP/M. Two early outliners, KAMAS (Knowledge and Mind Amplification System) and its cut-down successor Out-Think (without programming facilities and retooled for 8080/V20 compatibility) were also written for CP/M, though later rewritten for MS-DOS. Turbo Pascal, the ancestor of Borland Delphi, and Multiplan, the ancestor of Microsoft Excel, also debuted on CP/M before MS-DOS versions became available. Visicalc, the first-ever spreadsheet program, was never made available for CP/M. Another company, Sorcim, rose to the challenge and created its Supercalc spreadsheet for CP/M, which would go on to become the market leader and de facto standard on CP/M. Supercalc would go on to be a competitor in the spreadsheet market in the MS-DOS world. AutoCAD, a CAD application from Autodesk debuted on CP/M. A host of compilers and interpreters for popular programming languages of the time (such as BASIC, Borland’s Turbo Pascal and FORTRAN) were available, among them several of the earliest Microsoft products.

CP/M software often came with installers that adapted it to a wide variety of computers. Most forms of copy protection were ineffective on the operating system, and the source code for BASIC programs was easily accessible. The lack of standardized graphics support limited video games, but various character and text-based games were ported, such as Telengard, Gorillas (video game), Hamurabi, Lunar Lander, along with early interactive fiction including the Zork series and Colossal Cave Adventure. A text adventure specialist, Infocom was one of the few publishers to consistently release their games in CP/M format. Lifeboat Associates started collecting and distributing user-written “free” software. One of the first was XMODEM, which allowed reliable file transfers via modem and phone line. The last significant program native to CP/M was the outline processor KAMAS.

Disk formats

While the 8-inch single-density floppy disk format (so-called “distribution format”) was standardized, various 5 1/4-inch formats were used depending on the characteristics of particular systems and to some degree the choices of the designers. CP/M supported options to control the size of reserved and directory areas on the disk, and the mapping between logical disk sectors (as seen by CP/M programs) and physical sectors as allocated on the disk. There were many ways to customize these parameters for every system but once they had been set, no standardized way existed for a system to load parameters from a disk formatted on another system.

Certain disk formats were more popular than others. The Xerox 820’s became widely supported, for example; much software was available on it, and other computers such as the Kaypro II were compatible with the format. No single manufacturer, however, prevailed in the 5 1⁄4-inch era of CP/M use, and disk formats were not portable between hardware manufacturers. A software manufacturer had to prepare a separate version of the program for each brand of hardware on which it was to run. With some manufacturers (Kaypro is an example), there was not even standardization across the company’s different models. Because of this situation, disk format translation programs, which allowed a machine to read many different formats, became popular and reduced the confusion, as did programs like Kermit which allowed transfer of data and programs from one machine to another using the serial ports that most CP/M machines had.

The fragmented CP/M market, requiring distributors either to stock multiple formats of disks or to invest in multiformat duplication equipment, compared with the more standardized IBM PC disk formats, was a contributing factor to the rapid obsolescence of CP/M after 1981.

Source code releases

In 2001 Caldera released CP/M’s source code under an open source license, allowing redistribution and modification, via Tim Olmstead’s “The Unofficial CP/M Web site”.


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