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Cp/M Operating System By Digital Research

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CP/M Operating System by Digital Research

History of CP/M 3

History of the Personal Computer 3

Who was Gary Kidall? 4

CP/M вЂ" OS 5

User interface 6

File Management 6

Device Management 8

The Disk Drive - BIOS versus BDOS 8

Memory Management 9

Communication Services 10

About the CP/M museum online for further research 11

Reference 12

History of CP/M

History of the Personal Computer

The first microprocessor chip was created in 1968 by the Intel Corporation. The 4-bit chip, 4004, was designed for the Busicom 1141-PF calculator. This lead to the first personal computer, the Mark-8, designed in 1974, based on the 8-bit Intel 8080 chip. 1975 brought the first assembled personal computer named the Altair 8800 from Micro Instrumentation and Telemetry Systems (MITS); it was based on the 8080 chip, but had no keyboard or display. The first useful microcomputer was the IMSAI 8080, which was targeted for small business users, had a floppy drive and used the CP/M operating system developed by Gary Kildall while working at Intel, but then Gary and his wife Dorothy founded Intergalactic Digital Research, Inc to market and sell CP/M as the first microprocessor operating system. Tandy (Radio Shack) then introduced the TRS-80 which used CP/M to control the 8080 processor clone (the Zilog Z-80). In 1976, two companies changed there names, the first was Intergalactic Digital Research, Inc to Digital Research, Inc, and the second was Traf-O-Data to Microsoft. While Digital Research worked on developing the CP/M operating system, Microsoft worked on programming languages for computers using the Intel and Tandy chips and the CP/M operating system. In 1979 Intel introduced the 8088/8086 16-bit microprocessor. Tim Patterson at Seattle Computer Products, instead of waiting for Digital Research to release its 16 bit version of CP/M, wrote QDOS using Microsoft’s Altair Disk BASIC, which was mostly a copy of CP/M with a new file and disk management features. In 1980, Microsoft then licensees QDOS from Tim Patterson and made a deal with IBM naming it PC_DOS and then marketing it as MS-DOS, which Microsoft then licensed to other computer manufacturers (OEM’s) like Compaq.

Who was Gary Kidall?

Gary Kildall was born in 1942 and died in 1994. “Gary was the first person to interface a disk system to a microcomputer and create an operating system for it. He changed what had previously been a circuit designed for process control applications into a fully functional computer. Microcomputers now did tasks previously done only on minicomputers and mainframes. The world changed dramatically because of his work.”

In 1972 Gray received a Ph D in Computer Science from the University of Washington, and then joined the Navy. The Navy appointed Dr. Kildall as the Computer Science Instructor at their Pos-Graduated school in Monterey, California, while there Dr. Kildall was hired as a consultant to create a programming language called PL/M for the IBM 360 and Intel 4004 chip. In 1976, Dr. Kildall became a full time consultant after his discharge from the Navy and started the business, Intergalactic Digital Research, Inc, when he created the CP/M Disk Operating System for several microprocessors manufactures and the in 1977 rewrote CP/M to be hardware independent by creating a BOIS module. The Dr. Kidall and his wife marketed the new CP/M-80 operating system $90.

Dr. Kidall also pioneered the development of the GUI for the PC called GEM (Graphical Environment Manager) in 1983 with the most well know product the use this GUI was “Ventura Publisher” from Xerox. He also was one of the first persons to work on the development of software drivers for CD-ROM interfaces.

“There is no doubt that Gary Kildall led the way in microcomputer software development. I wonder what Microsoft will do now that they no longer have Gary Kildall to lead the way for them?”


“CP/M was designed during the early years of the microcomputer age, when systems had typically 64K of memory or less, and the only mass storage that was affordable were floppy drives. In its original versions, CP/M 1.0 thru 1.4, the operating system required an intel 8080 (or compatible chip), 20K of memory minimum, and one or more IBM-compatible single-sided single-density diskette drives. These drives stored about 240K of usable data each on an 8-inch diskette. Rarely did a system during this period have as much as 64K, with 32K or 48K being more typical. A 16K memory card could easily run you in the range $300-400 US dollars, making a full 64K cost around $1,600. Starting with CP/M version 2.0 in 1979, an experienced programmer could change the customizable BIOS to support almost any format floppy drive, 5 1/4 or 8 inch, and hard drives up to 8 megabytes in size. The system suppported up to 16 such drives. Eventually, as expertise developed in the field, BIOS writers because imcreasingly creative, and built in support for interrupts, real time clocks, bank-switched memory above 64K, variable format disks "on the fly", and many other options. By this time, CP/M was mostly being run on Z80-based systems with a minimum of 64K. The price for a fully configured Z80-based CP/M system with some useful business software was around $2,000 to $3,000 US dollars in 1981, arguably the peak year for CP/M usage in the world.”

User interface

The user interface for CP/M is a command line and a small number of support programs which are as follows:

• ED вЂ" a program to edit files

• PIP вЂ" a program to copy files

• ASM and LOAD to create assembler programs

• DDT вЂ" to debug assembler programs

File Management




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