> From: Artful Codger
>
> Warning: Alt-X is a "greedy" algorithm

This is rubbish.

In Word 2000 I just typed ...

<Alt48>0 and I correctly got 00, as I expected

... and ...

0<Alt48> and again I got 00, again as I expected

> Furthermore, Alt-X doesn't work with all Windows apps, only with Word and its kin.

Again, this is rubbish. AFAIAA, it works in all situations where the resulting character would be acceptable to the software. It may be that some software ignores or rejects the result, because it can't handle the character set or because the input would not be valid (for example text where a number is expected), but AIUI the mechanism basically functions everywhere in Windows.

Your understanding of the mechanism is clearly flawed. The substitution is legacy behaviour from DOS and works at a very low level. Go into Word or a console prompt and try the following ...

Press and hold down <Alt>, type 48, release <Alt>, type 0. You will observe that the first zero appears as the <Alt> key is released! This shows it's nothing to do with the high-level software interpreting the succession of characters coming in from the keyboard queue, that would give us a single character corresponding to 480, it's being done by the low-level keyboard driver monitoring the state of the <Alt> key.