| It's not clear we want to get into the complexities of positive-logic
nand gates (à la TTL) being the same circuitry as
negative-logic nor gates; of positive-logic nor gates (à
la CMOS) being the same circuitry as negative-logic nand gates; of
nand gates being just positive-logic and gates with inverting
output, so they are also negative-logic or gates with inverting outputs;
of nand gates being just positive-logic or gates with inverting
input, so they are also negative-logic or gates with inverting inputs;
and an inverters being just an amplifier with a bubble on input or output but
not both; or any other methods of confusing the reader. (I'm sure I messed up
the equivalences somewhere in this paragraph. That's the complication I'm
talking about.)
And, or and not are easy to understand
for lay and knowledgeable readers alike; nand would require explanation
for a lay reader, and is harder to deal with for the knowledgeable, even if he
has learned to automatically deMorgan the nand logic, by force of
habit.
The "negative-logic bubble on all ends of the line, or no end"
complication helps ameliorate the confusion when using the and with
bubble on the left and or with bubbles on the right symbols drawing
schematic circuit diagrams, but there's no corresponding complication for logic
formulas and equations. There are standard symbols for and (∧ for
competent character sets, * for less competent) and or (∨ or +), and
common symbols for not (postfix or prefix /, prefix ~ and ¬). I know
of no standard or even common symbol for nand or nor: I've used
#, but that's really a pain.
Let's just keep it simple. Certainly, a
universal primitive, like nor or nand has some appeal in theory,
but in practice or (especially) for tutorial purposes, it's less than
ideal. ---
--Bill. NAL: question the answers, especially mine. [ Reply to This | Parent | # ]
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