First Microcomputer OS: CP/M - Computerphile

CP/M was the first microcomputer OS, yet it lost out to DOS and never recovered the ground. Spencer Owen explains

EXTRA BITS - Using CP/M: Coming Soon!

This video was filmed and edited by Sean Riley.

[TDGalea]

Gary Killdall was great on Computer Chronicles. Absolutely loved watching him and the rest on the show.

[peteranderson]

That's not exactly what happened. Microsoft originally had no intention of supplying an OS to IBM. When IBM asked Microsoft to provide an OS for them, Bill Gates directed them to Digital Research which was working on a 16 bit port of CP/M at that time. IBM then went to Digital Research to negotiate a license for the 16 bit version of CP/M. What happened next changes depending on who you ask or which source you read, but suffice to say that IBM did not go with CP/M.

Bill Gates became nervous that IBM might leave the personal computer market entirely and, in a panic, told IBM that they could provide an OS for them after all. The only problem was that they actually didn't. What they did have was knowledge of another 16 bit port of CP/M that was being written by company called Seattle Computer Products. SCP called the port QDOS, which stood for Quick and Dirty Operating System. Microsoft bought QDOS, which they renamed MS-DOS for MicroSoft Disc Operating System, for a paltry $25, 000. Microsoft never informed SCP of why they were purchasing QDOS because they were already under a non-disclosure agreement with IBM for other products that Microsoft was supplying them for their PC.

Microsoft then informed IBM that they had an OS to use instead of Digital Research's 16 bit CP/M. However, instead of selling the rights for MS-DOS to IBM, Microsoft would license a copy to IBM for each PC that they made and would bundle it in with the computer. This allowed Microsoft to sell MS-DOS to the IBM PC clones that appeared in the years after its release.

The rest, as they say, is history.

[DimensionDude]

One of the last iterations of CP/M was CP/M 68K, developed for the Motorola 68000 microprocessor. It was the native operating system of the ill-fated Dimension 68000, the logo for which I have adopted as my avatar. It bears no relationship whatsoever to the Dell Dimension line of PCs.

[TheJamesM]

I don't know much about CP/M, but if I'm not mistaken it's probably partially responsible for the place the backslash character has in the public consciousness today.

As I understand it, CP/M (or at least the version DOS was based on) didn't have a directory structure. Commands could take arguments, and these were introduced by a slash character. DOS followed this format closely (or ripped it off, if you prefer). When DOS 2 came around, they wanted to introduce a directory structure like what was available in Unix. Unix used a dash to introduce command arguments and the slash as its directory separator, but wanting to avoid compatibility problems with CP/M and the earlier version of DOS, Microsoft offered the visually similar backslash as an alternative.

The backslash isn't a character that exists naturally in any human language, but was originally included on some keyboards as something that could be combined with a slash to form a the logical AND and OR symbols ∧ and ∨. It was included in the ASCII standard, but probably would otherwise have remained a relatively obscure character outside of serious computing.

Cut forward a few years, and Windows has taken over the world. Millions of people use it and are exposed to countless backslashes every day. Gradually confusion sets in, and people start to refer to the traditional slash character as a "forward slash". Others start confusing the backslash for a regular slash and use it in sentence text, saying things like "this\that". Then along comes the World Wide Web, and suddenly people have to contend with both slashes and backslashes in logical paths. Some people put backslashes in URLs; others just refer to the slashes as backslashes. Web browsers are programmed to automaticallu convert one to the other, and on and on.

It's a mess, and you can trace it back to a few pragmatic decisions stemming from the seemingly small, innocuous and arbitrary decision all that time ago, to use the slash as the symbol for command arguments in CP/M.

(To be fair, backslash nonsense has probably passed its peak now, with the Web probably having more influence on most people than any OS, and mobile device software keyboards hiding the backslash away with symbols not commonly required in human communication. Still, I think it's a fascinating case of cause and effect.)

[briandecker]

Computerphile you are much better than this! Gary did not pass until 1994 - and despite the Microsoft debacle Digital Research continued to revenues in the hundreds of millions of dollars throughout the 80's. Gary went on to develop Concurrent DOS, the file protocols that were the basis for CD-ROM technology, core technology for wireless connectivity and ultimately sold Digital Research to Novell for $120 million. His estate was valued in excess of $300 million when he passed - while not the billions of Gates he was hardly a nobody.

[nigelkingsley-lewis]

I understood that MS Dos was based on QDOS (quick and dirty operating system) which was basically a rip off of CPM.

[maniakaz]

As someone who still has (and uses, for fun) CP/M machine (Kaypro) I was hoping for more about CP/M itself.

[BlankBrain]

My only contact with CP/M was embedded in a very early Xerox laser printer. Xerox ran a proprietary printing language on top of it. The company I worked for at the time had a large amount of code that included hard-coded Xerox printing instructions. When the Xerox printers were no longer maintainable, I found a vendor that supplied a product to convert Xerox printer streams to HP PCL via a PC front-end. This worked for several years until all the Xerox-infused software was replaced in a Y2K push.

[okaro]

When I was in school in the early 80s we had a Televideo CP/M machine. It had the main computer that handled disks and two work stations that actually run the programs. It could support up to six work stations. The main unit had a 10 MB hard disk and a 320 KB floppy drive. The system with the software was about 40000 € in current money. Floppy disks at the time were something like 14 € in current money.

[BG_Dave]

Gary deserves his own video. Along side McAfee, he's a fascinating character.

[arvizturotukorfurogep]

Wait what!? The court found that code parts were taken from CPM/M in DOS? Where did you get that? Recently (about five years ago) it was all over the tech news sites that the code of the two OS was compared with an AI and it found that no code was stolen!

[PhilMace]

I worked with CPM. It had a big down side in the way it stored files that dos over came. That is why we moved to dos. Much better file storage structure. I think each section of CPM took a file. The next file saved. Required a new alocatio so the storage was not utilized in cpm.

[lohphat]

The TRS-80 had CP/M releases too and the native TRSDOS took cues from CP/M for its commands and file naming conventions.

[bamdadkhan]

okay what is that 65% keyboard on the desk? : )

[paulwratt]

MS-DOS v1 is call compatible with CP/M 2.2, which is why the 8-bit version (MSX-DOS v1 not v2) can run CP/M binaries unchanged.

[richardtwyning]

Gary Kildall has always been a hero of mine. Such a tragic way he died. Bill Gates was an amateur at the side of Gary Kildall. Really enjoyed watching the Computer Chronicles recently after discovering them on YouTube.

[matthehat]

I need to dig out my RC2014 again and do stuff with it

[jeanbonnefoy]

recalling dear memories of my first word processor computer (an Olivetti ETV 500 with two 5"1/4 floppy drives) running on cp/m 1.4 then upgraded to cp/m 2.2... twas in april 84! I remember there was an upgraded version of that os, called mp/m, used for networking. Some two years later, Olivetti swapped to DOS (2.11 was my first version of it, the first able to accommodate the new Sony 3"1/2 floppy format). DR-DOS then MS-DOS were in fact a sort of "mirror universe" copy of CP/M, meaning that the main difference simply was in the inverted syntax (like copy B: A: meaning copy A: B:) but the main command lines (dir, copy, del, format, etc. were strictly the same!

[rabidbigdog]

Through the power of Google, I can't find the 2002 court ruling mentioned? Tim Patterson has continuously denied directly copy/pasting CP/M bits for QDOS.

[cpcnw]

What is the model of the grey / white keyboard?