Digital Research · Christian

CP/M

operating system

Released: —
Platforms: Intel 8080 Intel 8085 Zilog Z80 Zilog Z8000 Intel 8086
Genres: Christian
Developers: Digital Research Gary Kildall
Publishers: —

About

CP/M, originally standing for Control Program/Monitor and later Control Program for Microcomputers, is a mass-market operating system created in 1974 for Intel 8080-based microcomputers by Gary Kildall of Digital Research, Inc. CP/M is a disk operating system and its purpose is to organize files on a magnetic storage medium, and to load and run programs stored on a disk. Initially confined to single-tasking on 8-bit processors and no more than 64 kilobytes of memory, later versions of CP/M added multi-user variations and were migrated to 16-bit processors.

CP/M's core components are the Basic Input/Output System (BIOS), the Basic Disk Operating System (BDOS), and the Console Command Processor (CCP). The BIOS consists of drivers that deal with devices and system hardware. The BDOS implements the file system and provides system services to applications. The CCP is the command-line interpreter and provides some built-in commands.

The articlegameplay, story, development, reception

Development

Gary Kildall originally developed CP/M during 1974, 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. It was written in Kildall's own PL/M (Programming Language for Microcomputers). 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.

CP/M supported a wide range of computers based on the 8080 and Z80 CPUs. An early outside licensee of CP/M was Gnat Computers, an early microcomputer developer out of San Diego, California. In 1977, the company was granted the license to use CP/M 1.0 for any micro they desired for $90. Within the year, demand for CP/M was so high that Digital Research increased the license to tens of thousands of dollars.

Legacy

A number of behaviors exhibited by Microsoft Windows are a result of backward compatibility with MS-DOS, which in turn attempted some backward compatibility with CP/M. 3 filename conventions in MS-DOS (and early Windows versions) were originally adopted from CP/M. The wildcard matching characters used by Windows (? and *) are based on those of CP/M, as are the reserved filenames used to redirect output to a printer ("PRN:"), and the console ("CON:").

The drive names A and B were used to designate the two floppy disk drives that CP/M systems typically used; when hard drives appeared, they were designated C, which survived into MS-DOS as the C:\> command prompt. The control character ^Z marking the end of some text files can also be attributed to CP/M. Various commands in DOS were modeled after CP/M commands; some of them even carried the same name, like DIR, REN/RENAME, or TYPE (and ERA/ERASE in DR-DOS). COM are still used to identify file types on many operating systems.