Breaking News
News & Analysis

Was DOS copied from CP/M?

8/17/2016 11:00 AM EDT
More Related Links
View Comments: Newest First | Oldest First | Threaded View
User Rank
Does it matter?
DMcCunney   12/1/2016 12:06:12 PM
At this point, I think whether MS copied parts of CP/M for MSDOS is irrelevant.

MSDOS 1.X was based on a product called 86DOS from Seattle Computer Products, who made a line of early micro computers based on 8086 CPUs using an S100 bus.  IBM approached MS about an OS for the new IBM PC line, and at that point, MS didn't have one, so they bought an extant product that could be modified as a starting point.  86DOS was a CP/M derivative.

Whatever MS came up with, it would need a high level of CP/M compatibility.  Getting support for its new architecture required applications as well as an OS.  The PC would be seen as a bigger, faster and more powerful step up from existing CP/M machines based on Intel 8080 and Zilog Z-80 CPUs, and it would need to be easy to port popular existing CP/M applications like the WordStar word processor and Visicalc spreadsheet to the PC.  An OS that looked as much as possible like CP/M to the applications was a requirement. 

(And vestiges of that persisted long after.  For a long time, for example, MSDOS treated a Ctrl-Z char as an end-of-file marker.  That was a carryover from CP/M.  CP/M versions before 3.0 did not store the file size in a directory entry, so the OS needed a way to tell where the file ended when loading it.  I spent time back in the day getting apps to not place Ctrl chars as EOF markers when they wrote files, and to ignore them in input bec ause the file might not actually end there.)

Once upon a time, there was OS competition in the PC market.  IBM offered PC-DOS based on Microsoft's offering, but you could also get an X86 port of the UCSD P-System (already used on the IBM Displaywriter dedicated word processor system), and CP/M-86, a later Digital Research port of CP/M to the PC platform.

There were stories floating around that IBM had contacted DR about a version of CP/M before going with MSDOS, and that DR President Gary Kildall had chosen to fly his plane rather than meet with the IBM VP.  The more likely happening was a different report that DR had met with IBM and didn't like the licensing terms IBM was offering.

In any case, MSDOS won in the marketplace, and the rest was history.

The wide variation in platforms running CP/M meant that it needed to be configurable, and it's a fair bet vendors offering CP/M got at least some source to be able to make the changes required to support their hardware.  I don't know what MS got when they bought 86DOS from Seattle computer products, but some amount of source is a good bet.

Whether DR had grounds for suit against MS is kind of a pointless question.  They might have had grounds.  They chose not to sue back when they could have.









User Rank
Re: More Important Question...........Was Russian agat copy of Apple II
AnonymousU096i01   8/21/2016 7:15:58 PM
To get verilog for a 6502 I downloaded a project from opencores. It was an AGAT computer which had a 6502 module. It included a ROM image. Looking at the ROM image I noticed... heh!! this is really close to the 2K monitor ROM at F800-FFFF on an Apple II.

User Rank
More Important Question...........
Loser99   8/18/2016 12:03:34 PM
Who cares?


30+ years ago?

nobody cares.


might as well talk about vacuum tubes instead.



User Rank
And what about the IBM-PC ?
green_ee   8/18/2016 11:33:51 AM
I recall a project in Byte magazine, very early 1980s (yes, back when computer hobbying required skills like wire-wrapping, soldering, electronics knowledge, etc) about an 8088-based computer project. Soon afterwards, IBM introduced the first PC, which was also 8088-based. To this day, I still wonder if that project is the seed that sprouted into the PC industry as we know it today.

User Rank
sixscrews   8/17/2016 11:41:38 PM
As an early CP/M user and a later MS-DOS user I was stunned by the symmetry between the two OS breeds.  Similar calls, arguments, memory layouts - who can dispute that MS-DOS is a CP/M rip-off.  But that's history - just like Guderian took DeGaulle's tank warfare book and defeated the French in 1940 - pay attention to what you say/build/release because somebody else will take it.

On the other hand (or paw if you are a Kzin) Gary Kildall didn't exactly jump on the IBM opportunity.  As I understand he didn't bother to show up for the meeting with the IBM reps.  Later he a bit lackadaisical about dealing with the IP issues arising from MS-DOS.

At the time, 1983, software seemed like an adjunct to hardware - more of an annoyance than a critical component of a system and Kildall's company, Digital Research, was messing with a version of CP/M that was supposed to support multiple concurrent processes - I bought it but it didn't run on my hand-built Z-80 system that, at the time, was a 'hot box.'

Bill out foxed Gary and the rest is history.  Tough .....


User Rank
would not doubt it one bit
cps1   8/17/2016 12:24:38 PM
Would not doubt it one bit.  Between him, Mark Z. and others over there. 

Most Recent Comments
rick merritt
Tim R Johnson
Most Recent Messages
3:31:42 PM
Like Us on Facebook
EE Times on Twitter
EE Times Twitter Feed