CP/M is a set of operating systems, those starting from approximately 1974 of digitally Research Inc. under Gary keel-Kiel were developed. CP/M was (beside the Unix conceived for higher performance computers) the first platform-independent operating system. With the arising of MS-DOSCP/M lost its meaning.

CP/M without closer designation stands usually for CP/M-80, the original starting from 1974 developed version for the microprocessors Intel 8080 and Zilog Z80. The last version of CP/M-80 was called CP/M pluses. CP/M-86 was a Portierungon the processors Intel 8086/8088. With CP/M-68K followed a little successful variant for Motorola the 68000.

The acronym CP/M originally meant control Program/monitor (D. h. Control program monitor), became later however than control Program for Microcomputers reinterpreted.

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the core of CP/M forms the BIOS(Basic input/output system), which makes a standardized interface available for hardwarenear tasks, particularly to input and output. Only this part of the operating system had to be adapted to the respective type of computer, which was normally done via the manufacturer. The remaining partscould be taken over without large changes, since they develop only on the functions of the CP/M core.

The standardized functions of the BIOS used of the hardware-independent BDOS (basic disk operating system), which “higher” functions makes available, particularly to the file management.This accesses the hardware only indirectly over the BIOS, whereby hardware independence is realized.

The BDOS again used by the CCP (CONSOLE COMMAND Processor), which receives the instructions of the user, some simple instructions implements, and otherwiseappropriate program loads and starts.

Application programs communicate with the hardware usually only over the continuous BDOS and over the standardized points of re-entry point of the BIOS, and are thus portable. However the application programs for CP/M for speed and storage location reasons often are in assembler languagewritten and as source code were published only rarely, so that portability is given within a processor family in practice only.

This structure was taken over later also by MS-DOS: Here the parts described above are called now IO.SYS, MSDOS.SYS and COMMAND.COM. At all leanedthe first version of MS-DOS very strongly at CP/M on, the main change was an improved file system.

weak points

a large weak point of CP/M it was that there was no uniform diskette format for 5.25-Zoll-Disketten. The only “official”Format was a 8-Zoll-Format, so that after large disappearing of the unmanageable 8-Zoll-Laufwerke the exchange of disks between CP/M computers of different marks became to impossible practically very with difficulty. Also the screen and printing control were not uniform in CP/M systems (CP/M was original forscreenless, teleprinter - based systems developed), so that one had to often communicate the used screen and printer to this before the first use of a commercial program - and for it to hope that the program also knew the appropriate models. Later CP/M systems emulated frequentlywidespread screen types, so that as much as possible software could run on it.

With the rapid waste of the memory prices starting from approximately 1981 also the restriction on 64 kilobyte directly usable memory became a problem - debt was here however not CP/M, but those8 bits - processors, on which it was mainly used. Also the bad suitability for non removable disks, above all the not existing sublists, braked CP/M starting from approximately 1982 increasingly out.

1983 appeared to 3,0 with CP/M pluses the last versionthe classical 8080er-CP/Ms, whatever now by means of bank Switching supported more than 64 KB memory. This version is usually-sold the world-wide owing to the Commodore 128, with which it was provided, could however, which concerns the actual use, notmore to the popularity of the simpler CP/M 2,2 tie.


the early 1980er years, on which CP/M was used, had typical hardware typical computers a CCU Zilog Z80 (upward compatible to Intel 8080) with 2 to 4 MHz, 64 or 128 KiB main storage, a in-colored screen, which could represent 80×24 indication text ( however no diagram), or two floppy drive assemblies with 8 a tariff or a 5,25-Zoll disks, possibly. also a non removable disk with approx. 5 MT.

CP/Malso its computers built by many amateur handicraftsmen on one used. Still if S100 - systems as for instance the IMSAI, then if well-known commercial CP/M computers of the later years of the Osborne and the KayPro were - dominated models in the early period; on Apple the IICP/M was used frequently by means of an additional Z80 - processor map: Apple CP/M.

Also on many home computers CP/M could be used, for example on the cutter CPC and the Commodore 128; in practice it became however rather rarely on home computersused, since these along-brought still another additionally in each case their own operating system, which was co-ordinated with the respective hardware better and thus particularly for the production by computer games was much better suitable than CP/M. Under CP/M against it rather typical application programs becamelike text processing, spread-sheet analysis, small data bases and programming languages such as Pascal used.

In the GDR CP/M under the designation became SCP for U880 (Z80) and/or. SCP86 for 8086-Hardware used for data recording equipments and office computers (at that time manufacturer Robotron Karl Marx city/Dresden/Sömmerda/Zella Mehlis). With the industrial selling broadcastand television (Kombinat/BT Erfurt) e.g. existed. a complete invoicing (hardware Z80/64KB/4x disk LW 800KB) those approx. 15000 articles to administer knew. Later a CP/M compatible operating system developed with OS/M in the GDR.

postage run gene of CP/M

[] if CP/M-86

works on

beside the 8080/Z80-Version of CP/M, above all CP/M-86 attained practical meaning, a CP/M version for 8086 - and 8088 - CCUs von Intel.

CP/M-86 had 1981 quite the chance, for the standard operating system IBM PC, first Personal computers of IBM to become. Due to from until today disputed circumstances got CP/M however a competitor: MS-DOS by Microsoft. Although IBM left at first the choice of the operating system to the customer, MS-DOS sat down - in ofIBM delivered variant PC DOS was called - due to its lower price of 40 dollar quite fast against the substantially more expensive CP/M-86 through, particularly since application programmers Software developed first for both platforms. MS-DOS is an advancement of QDOS von Seattle computer Products,was conceptionally strongly ajar against CP/M-80 (see also MS-DOS). After Microsoft had made several months adjustments to the IBM PC hardware, it bought the rights at QDOS, which had been renamed in the meantime in 86-DOS briefly before its conception finally.

1988a strongly developed further, completely MS-DOS-compatible version was brought out of CP/M-86 as DR-DOS and again made Microsoft some years long serious competition. When DR-DOS got ready to, also with system Distributoren as serious alternative to MS-DOS to be considered, one ensuredError message in a Vorabversion graphic operating system essay of the Windows 3,0 under DR-DOS for disconcerting. Although Windows ran after the way clicking of the error message problem-free under DR-DOS, arose doubts to the complete Kompatiblität from DR-DOS to MS-DOS. Of this call could itselfDR-DOS never again correctly release. It speaks much for the fact that Microsoft had intentionally inserted this error message, in order to arouse at its customers the impression of the not hunderprozentigen Kompatiblität between DR-DOS and MS-DOS. In later legal proceedings was from an appraisalthe speech, which occupies this assumption. Since the process in a comparison ended, the debt of Microsoft was however never judicially determined.


the Portierung on Motorola 68000, called the CP/M-68k, even no large commercial success,became the basis for TOS, the operating system of the Atari pc.


existence CP/M still from three monolitischen blocks, then existed in turbo-DOS a high-modular, compatible system, which possessed multi-processing abilities and multitasking.


A multi-user version of CP/M. Several users could work over ASCII terminal at the same time on a computer.

acquaintance of programs for CP/M

  • WordStar of MicroPro, a text processing.
  • Microsoft multi-plan by Microsoft, a spread-sheet analysis.
  • Dbase II of Ashton doing, a data base software.
  • Turbo Pascal of boron country, a development environment for the programming language Pascal.

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