Comment by kees99

> just plain wrong -- e.g. floating inputs or missing resistors

TTL logic gates have no problem with floating inputs. Those are interpreted as logic high. [1]

This is fairly self-evident from looking at a typical TTL gate schematics. [2]

Some "TTL-compatible" CMOS parts (including 65C02) have internal pull-ups on inputs, to match this quirk. [3]

Granted, it is a bad habit to develop, given that nearly all "modern" logic (i.e. of past 30+ years) is CMOS with no "TTL compatibility", and floating inputs are a big problem there.

[1] https://electronics.stackexchange.com/questions/683051/outpu...

[2] https://upload.wikimedia.org/wikipedia/commons/thumb/d/d4/TT...

[3] https://wilsonminesco.com/NMOS-CMOSdif/