Re: "Not" gate

Posted by WBahn on Jan 31, 2021; 7:34pm
URL: http://nand2tetris-questions-and-answers-forum.52.s1.nabble.com/Not-gate-tp4035528p4035592.html

It a "necessary but not sufficient" condition.

If you don't get that message, it means that there is something wrong with your code (assuming the test script is correct, which at this point is a very safe bet).

But with the exception of the simplest gates (and the Not gate does fall into this category) it is difficult if not impossible for the test script to test everything, so it just "spot checks" for the more common errors that the authors thought students were likely to make. Hence it's possible to pass the tests for a chip but for it to have undetected errors that don't make themselves known until later.

If you think that will make tracking down the problem that much more difficult when it raises it's ugly head, you are absolutely correct. You can ask Intel about that with regard to the Pentium floating point bug that cost them nearly half a billion dollars to fix.