On Wed, 16 Sep 2009 07:16:13 -0400, you wrote:

>After all, it *always* has to be done this way.  It's not clear
>though what exactly these resistor are supposed to be in series with.

If you go back to TTL (pre LSTTL) abs max supply voltage is 7v, abs max
input voltage is 5.5v (at least that's what the data sheets say). You would
pull inputs high through a current limiting resistor to provide more safety
margin for excess supply voltage. No resistor needed to pull them low. 

Another reason would be for automatic test allowing you to force unused
inputs, the argument being you can't test a chip is good without testing
all of it including the inputs and bits not actually used in the circuit.
Popular with test departments because regardless of what circuit it was in
they could just tell the ATE that is a 7432 - test it.

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