An operating system from Digital Research which was the standard on most S-100 bus systems. It might have been used on the IBM-PC as well, but Bill Gates sold them on PC-DOS instead. (It has since been shown that PC-DOS contains a fair amount of code suspiciously identical to that of CP/M. Digital Research never sued.

An operating system written by Gary Kildall at Intel. Intel didn't see a need for it, so Kildall founded Digital Research and sold the OS as CP/M. CP/M was geared towards machines based on the Intel 8080. Later Digital Research also created CP/M-86 (for use on Intel 8086/8088 machines) and CP/M-68k (for use on 68000 based machines). Neither were as popular as CP/M-80. CP/M-80 was the most popular OS for micro-computers until the rise of PC-DOS.

Windows NT vs. CP/M

Microsoft has come out with a number of benchmarks and comparison papers championing the fact that Windows NT is much better than Linux. I find such comparisons fascinating, but rather than rehash this argument, I've decided to create my own comparison. Not of Windows NT vs. Linux, that's been done. But of Windows NT vs. CP/M.

CP/M for those of you who don't remember was one of the first portable operating systems. It ran on 8 bit 8080 class hardware, and was a single user, floppy based system. (Later versions actually could access a hard drive.)

Two systems were selected for this comparison. The CP/M system is a Kaypro-II running a 2MHZ Z80, with 64K of memory and dual 360K 5-1/4 floppies. The Windows NT system runs quad 500 MHZ Pentium Processors, with 2GB of memory and 1TB of disk space. This particular configuration was chosen because Microsoft seems to like to use a system like this for all its benchmark comparisons.


Performance is one key issue in any comparison. I do a lot of writing, so word processing performance is extremely important to me. The CP/M system with Word* and after a 15 second boot Word* let me write documents as fast as I could type. In my two minute test, I could enter about 210 words.

The Windows NT system running Microsoft Word also could accept input as fast as I could type, but it took a whole minute to boot up. Thus I could enter only 120 words in my test. So we can conclude that CP/M is 75% faster than Windows NT for word processing.

Let's talk about spreadsheet performance. CP/M with Calc* will balance my checkbook just as fast as I can input the data. Counting the boot time, that means that I can enter about 17 transactions in a two minute test. With Windows NT with Excel, I get only 10 transactions a second. So as far as spreadsheet performance goes, CP/M is 70% faster than Windows NT.

Conclusion: CP/M provides superior overall performance for common office applications.


CP/M is an extremely secure system. It relies on the physical security methodology. You store the operating systems, programs, and private date on 5-1/4" floppies. You want to use them, put them in the machine. No one can get to your data from the outside through a network because CP/M has no network. You want to secure your data, take the floppies out and lock them up. Want to share data, hand the floppies to another person. Note: This security method allows the user a wide variety of personal authentication schemes such as drivers license, passport, or personal friend known to you.

What's even better since we are running on a two floppy system, we can put our software on one floppy and the data on the other. The software floppy can be write protected, and nothing we do can change any of those files.

Windows NT relies on file system security and passwords. There have been lots of studies about the weaknesses of passwords. Any system that relies passwords in insecure. In addition Windows NT contains a tremendous security hole called the Administrator account. Anyone logged in to this account can easily read and write all your files.

Add to that that Windows NT connects to a network and allows remote access and you have big security problems. There have been hundreds of security problems reported for Windows NT such as viruses, E-Mail viruses, break ins, denial of service attacks, and many others. None of these problems have affected CP/M.

Plus Microsoft relies on operating system file protection to keep you from modifying system files. This means that you must know what files to protect and rely on software to provide your protection. Hardware protection is much easier to configure and provides much more reliable protection. Windows NT makes no use of hardware protection for system files.

Microsoft likes to trumpet the fact that Windows NT is certified by the government for C3 security. What they leave out is that that was only for a certain version of Windows NT (which they no longer support) and a certain hardware configuration (which had no network card.) In the real world, a typical Windows NT installation would never come close to getting C3 certification.

CP/M however could easily be certified. It has a very secure network because it has no network capability. It also has set of keys that you can press that return you to the "secure command server". (It's called the reset button.) These are the big features of C3 security and CP/M has them. The reason that it does not have C3 certification is that no one wants to pay the big bucks to get it certified.

Conclusion: The security of CP/M is vastly superior to Windows NT.


As far as I know the CP/M system for my Kaypro has not needed an upgrade or patch for the past ten years. Also the operating system has no reported bugs that can crash it. It is small, simple and very stable.

During that time Microsoft has two major releases of Window-NT, at least 5 service packs and is planning on replacing the system with a new version next year. In addition to this there are a large number of bugs out there that Microsoft has yet to fix. Many companies reboot their Windows NT systems weekly to avoid system crashes that come when you leave Windows NT running for too long.

Conclusion: CP/M is much more stable than Windows NT.

Cost of ownership

You can probably pick up a Kaypro-II with CP/M, Word* and Calc* at a garage sale for about $10. Or you can go to an auction site and pick one up for about $100-$200.

On the other hand a Window-NT system in the configuration that Microsoft likes to use for benchmarking will probably cost you about $100,000. This includes the price of the hardware, software, and the cost of hiring a team of Microsoft Engineers for three months to tune your system for optimal performance.

Conclusion: The cost of ownership of CP/M is much, much lower than Windows NT.

Customer Testimonials

But let's talk about real world experience. CP/M has hundreds of customer testimonials all describing how useful and easy to use this operating system is, while Microsoft Windows NT is only able to provide anecdotal evidence.

Note: We are using the definition of these terms as defined by Microsoft Marketing.

Customer Testimonials Stories about how well the operating system works for the operating system you like.
Anecdotal Evidence Stories about how well the operating system works for the operating system you don't like.

Conclusion: Since CP/M has Customer Testimonials and Windows NT has only Anecdotal Evidence, we must conclude that CP/M is vastly better.


These results show that in every comparison category that CP/M is at least as good as Windows NT and frequently outperforms the Microsoft operating system.

Another conclusion we can draw from this is that if you come up with the answer, a good writer can come up with a question that produces the desired result. Comparisons like this one should always be scrutinized for relevance and bias before you put any faith into them.

Coming soon, we will compare a Windows NT system vs. a brick. I'm not going to give away the ending, but I'm going to bet that the brick will win.

cowboy = C = CPU Wars

CP/M /C-P-M/ n.

[Control Program/Monitor; later retconned to Control Program for Microcomputers] An early microcomputer OS written by hacker Gary Kildall for 8080- and Z80-based machines, very popular in the late 1970s but virtually wiped out by MS-DOS after the release of the IBM PC in 1981. Legend has it that Kildall's company blew its chance to write the OS for the IBM PC because Kildall decided to spend a day IBM's reps wanted to meet with him enjoying the perfect flying weather in his private plane. Many of CP/M's features and conventions strongly resemble those of early DEC operating systems such as TOPS-10, OS/8, RSTS, and RSX-11. See MS-DOS, operating system.

--The Jargon File version 4.3.1, ed. ESR, autonoded by rescdsk.

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