Actually it was shipped. “Microsoft disabled the AARD code for the final release of Windows 3.1, but did not remove it, so that it could have become reactivated later by the change of a single byte in an installed system.” [1]

[1] Schulman, Andrew; Brown, Ralf D.; Maxey, David; Michels, Raymond J.; Kyle, Jim (1994) [November 1993]. Undocumented DOS: A programmer's guide to reserved MS-DOS functions and data structures - expanded to include MS-DOS 6, Novell DOS and Windows 3.1 (2 ed.). Addison Wesley. ISBN 0-201-63287-X.

Is it shipped if it cannot execute under any conditions? Philosophical question I'm afraid.

The code? Yes

The feature? No

The company that makes GTA was sued for content that was not accessible in the game.

Anybody can sue anyone for anything. I could sue Rockstar for not having enough nudity in GTA; that does not imply guilt or lawbreaking on their part.

The suit you mentioned was settled out of court for a tiny amount, basically nuisance value, with no finding or admission of wrongdoing.

They probably shouldn't have?

> could have become reactivated later by the change of a single byte in an installed system.

Is that not a condition under which it could be executed?

Only if the application has code to change that byte. “It could be changed by a patch” doesn’t count as a condition under which it could be executed, because a patch can make any change it wants to. You wouldn’t say “there’s a condition under which Windows will wipe your hard drive and every visible network share” just because someone can write code to do that.

As documented in the excellent book "Undocumented DOS", whose red cover I can still picture. (Noted in the article, but it was a good book that I still recall fondly.)

I can touch my copy without moving from the chair that I am sitting in. (-:

Is it now your monitor's support?

No. It's on the bookshelf next to Petzold, and below the other Petzold book, that I suspect far fewer have read, on the shelf above. On the other side of the Lower Petzold is Undocumented Windows.

If you deduced from this that the shelves were divided into Windows and OS/2, the sad truth is that the lower shelf is slightly too high, and the books are divided by height differences that amount to millimetres in some cases. Lower Petzold fits; Upper Petzold does not. (-:

Thanks for the recommendation! Just bought a copy off eBay for $4 for my collection.

However it was present in the release shipped to reviewers, who wrote their reviews which including saying how windows worked better on ms-dos

IIRC, the author of "Undocumented DOS" discovered and disclosed this feature during the beta, before release.

It seems at least plausible, if not probable, that Microsoft disabled the xor encrypted bogus error message generating code in the release version as a result of this disclosure.