How to be successful? Of course, all you need to do is get up earlier, purr more often and carry more weight. However, there are people who decide to take a different path - that of fraud. Today I will tell a short story about how Microsoft finished off its competitor, Digital Research.

CP / M

I think that each of you has heard about MS-DOS, which is commonly called DOS. However, as much as this system was popular in Poland, it was not the only system from this family. We also had PC-DOS (which was actually MS-DOS, but developed by IBM) or the above-mentioned DR-DOS (FreeDOS appeared later, but it's also in this family of systems).

DR-DOS is an operating system created by Digital Research. It was created as a successor to another system - CP / M. IBM could not get along with DR, so they signed a contract to supply software from Microsoft. Microsoft decided to buy another operating system - 86-DOS and develop it for IBM's hardware. The similarities of MS and IBM's system to CP/M were so huge that DR wanted to sue these companies for copying their product. As compensation, IBM allowed Digital Research to sell the system alongside PC-DOS (IBM had the right not to use the MS-DOS name). However, IBM's and Microsoft's operating system was much cheaper than its counterpart which meant that CP/M began to be squeezed out of the market.

Digital Research's product was not fully compatible with IBM's, an initial plus began to turn into a minus as PC-DOS began to rule the personal computer market. Even later attempts to improve CP/M could not tip the balance. Simply put, DR systems were too expensive and IBM and Microsoft began to set the trends.


However, DR rolled up their sleeves and went into battle. The first thing they did, besides achieving compatibility with Microsoft's product, was to significantly lower the price and start introducing newer and newer features to the system - such as HMA support, allowing the system to handle more RAM than 640KB, and file compression. From now on, it was up to Microsoft to make newer and newer changes to keep up with DR-DOS, and they had to cut prices. Customers (and especially computer makers) were so interested in DR's product that they started offering DR's products widely.

If you're going to kill someone there isn't much reason to get all worked up about it and angry. Any discussions beforehand are a waste of time. We need to smile at Novell while we pull the trigger.

When a user ran Windows 3.1 Beta on his computer using DR-DOS he was horrified when the system informed him of a "non-fatal error". Every run of Windows or certain programs reported the problem.

This is a feature added at the request of Bill Gates. The message you see here is not a "real" error. Code was added in various parts of the operating system that detected what system it was running on and displayed the message. Of course, DR-DOS handled these programs without a problem and everything worked perfectly despite the error message. However, users of the system seeing such messages, according to the vice president of Microsoft - "(...) to do is feel uncomfortable, and when he has bugs, suspect that the problem is DR-DOS and then go out to buy MS-DOS".

In the final version of Windows 3.1, the code was disabled, but you could easily enable it by changing 1 byte, and rumours of DR-DOS malfunctioning spread around the world. Not even a patch to pass the "sieve" of AARD


DR-DOS was sold to Novell and eventually went to Calder. The first thing the company did when it bought DR-DOS (later Novell DOS) was to file a monopoly case against Microsoft for, among other things, AARD code and "bundling" Windows 95 with MS-DOS (Win95 was a DOS overlay, but installed Microsoft DOS by default, even though DR-DOS could very well have acted as a "shim"). We know from leaks in 2009 that Microsoft paid Caldera $280 million for his practices.

- CP/M image Wikipedia, from Digital Research website under PD license.

- Photo Novell DOS, Wikipedia, Ghettoblaster

- Photo of AARD from Wikipedia, from Betawiki under CC-BY-SA 4.0 license

- History of MS-DOS (Coleslav) [PL]

- Windows' Hidden Self Destruct Code (Nostalgia Nerd)