AARD code

AARD code

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AARD code

The AARD code was a segment of obfuscated machine code in the installer for a beta release of Microsoft Windows 3.1. The code ran several functional tests on the underlying DOS that succeeded on MS-DOS, but resulted in a technical support message on competing operating systems. The name was derived from the initials of Microsoft programmer Aaron Reynolds, who used "AARD" to sign his work. ("AARD" was found in the machine code of the installer.)^[1]^[2] Microsoft disabled the AARD code for the final release of Windows 3.1.

The rationale for the AARD code came to light when internal memos were released during the United States Microsoft antitrust case. Internal memos released by Microsoft revealed that the specific focus of these tests was DR-DOS. At one point, Microsoft CEO Bill Gates sent a memo to a number of employees, reading "You never sent me a response on the question of what things an app would do that would make it run with MSDOS and not run with DR-DOS. Is there [sic] feature they have that might get in our way?"^[3] Microsoft Senior Vice President Brad Silverberg later sent another memo, stating that "What the [user] is supposed 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"^[3]

Following the purchase of DR-DOS by Novell and its renaming to "Novell DOS", Microsoft Co-President Jim Allchin stated in a memo, "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."^[3]

Novell released a patch to enable the AARD tests to pass on DR-DOS and Novell DOS in 1994.^[4]

What had been DR-DOS changed hands again. The new owner, Caldera Systems, began a lawsuit against Microsoft over the AARD code, Caldera v. Microsoft, which was later settled.^[3]^[5]