4.2Gates95columns for the truth tables for the AND and NAND gates. They areopposite, row by row. The same is true for the OR and NOR gates.Review of Gate ProcessingWe’ve looked at six specific types of gates. It may seem to be a difficulttask to keep them straight and remember how they all work. Well, thatprobably depends on how you think about it. We definitely don’tencourage you to try to memorize truth tables. The processing of thesegates can be described briefly in general terms. If you think of them thatway, you can produce the appropriate truth table any time you need it.Let’s review the processing of each gate. Some of these descriptions arein terms of what input values cause the gate to produce a 1 as output; inany other case, it produces a 0.■A NOT gate inverts its single input value.■An AND gate produces 1 if both input values are 1.■An OR gate produces 1 if one or the other or both input values are 1.
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