Editing CP/M (section)

== Hardware model ==
[[File:Sanco 8001.jpg|thumb|Sanco 8001 computer, running under CP/M 2.2 (1982)]]
[[File:Commodore CP-M cartridge for the C64 (main).jpg|thumb|right|CP/M cartridge for the [[Commodore 64]] ]]

A minimal 8-bit CP/M system would contain the following components:
* A [[computer terminal]] using the [[ASCII]] character set
* An Intel 8080 (and later the 8085) or Zilog Z80 microprocessor
** The [[NEC V20]] and [[NEC V30|V30]] processors support an 8080-emulation mode that can run 8-bit CP/M on a PC-DOS/MS-DOS computer so equipped, though any [[PC clone]] could run CP/M-86.<ref name="CP/M-Emu"/><ref name="Davis_1985_NEC"/>
* At least 16 kilobytes of [[random-access memory|RAM]], beginning at address 0
* A means to [[bootstrapping (computing)|bootstrap]] the first [[Disk sector|sector]] of the diskette
* At least one [[floppy disk|floppy-disk]] drive

The only hardware system that CP/M, as sold by Digital Research, would support was the Intel 8080 Development System. Manufacturers of CP/M-compatible systems customized portions of the operating system for their own combination of installed memory, disk drives, and console devices. CP/M would also run on systems based on the Zilog Z80 processor since the Z80 was compatible with 8080 code. While the Digital Research distributed core of CP/M (BDOS, CCP, core transient commands) did not use any of the Z80-specific instructions, many Z80-based systems used Z80 code in the system-specific BIOS, and many applications were dedicated to Z80-based CP/M machines.

Digital Research subsequently partnered with Zilog and [[American Microsystems]] to produce Personal CP/M, a ROM-based version of the operating system aimed at lower-cost systems that could potentially be equipped without disk drives.<ref name="pcn19840114_cpm">{{ cite magazine | url=https://archive.org/details/PersonalComputerNews/PersonalComputerNews044-14Jan1984/page/n8/mode/1up | title=Plug-in CP/M coming | magazine=Personal Computer News | date=14 January 1984 | access-date=3 October 2022 | pages=7 }}</ref> First featured in the Sharp MZ-800, a cassette-based system with optional disk drives,<ref name="pcw198502_sharpmz800">{{ cite magazine | url=https://archive.org/details/PersonalComputerWorld1985-02/page/144/mode/2up | title=Sharp MZ-800 | magazine=Personal Computer World | date=February 1985 | access-date=3 October 2022 | last1=Hetherington | first1=Tony | pages=144–146, 149–150 }}</ref> Personal CP/M was described as having been "rewritten to take advantage of the enhanced Z-80 instruction set" as opposed to preserving portability with the 8080. American Microsystems announced a Z80-compatible microprocessor, the S83, featuring 8&nbsp;KB of in-package ROM for the operating system and BIOS, together with comprehensive logic for interfacing with 64-kilobit dynamic RAM devices.<ref name="practicalcomputing198406_cpm">{{ cite magazine | url=https://worldradiohistory.com/UK/Practical-Computing/80s/Practical-Computing-1984-06-S-OCR.pdf | title=Cheaper, simpler CP/M | magazine=Practical Computing | last1=Coles | first1=Ray | date=June 1984 | access-date=3 October 2022 | pages=43 }}</ref> Unit pricing of the S83 was quoted as $32 in 1,000 unit quantities.<ref name="microsystems198406_s83">{{ cite magazine | url=https://archive.org/details/microsystems_84_06/page/n15/mode/1up | title=AMI releases specs on CP/M microchip | magazine=Microsystems | date=June 1984 | access-date=25 March 2023 | pages=12 }}</ref>

On most machines the bootstrap was a minimal [[bootloader]] in [[read-only memory|ROM]] combined with some means of minimal [[bank switching]] or a means of injecting code on the bus (since the 8080 needs to see boot code at Address 0 for start-up, while CP/M needs RAM there); for others, this bootstrap had to be entered into memory using [[front panel|front-panel]] controls each time the system was started.

CP/M used the 7-bit ASCII set. The other 128 characters made possible by the 8-bit byte were not standardized. For example, one [[Kaypro]] used them for Greek characters, and [[Osborne Computer Corporation|Osborne]] machines used the 8th bit set to indicate an underlined character. [[WordStar]] used the 8th bit as an end-of-word marker. International CP/M systems most commonly used the [[ISO 646]] norm for localized character sets, replacing certain ASCII characters with localized characters rather than adding them beyond the 7-bit boundary.