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What is 39 and 40?

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I don't see a 39 or a 40.

29 is an XNOR gate (NOT XOR).

30 is the NOR gate (NOT OR).

Can you explain that to me?

A two-input XOR gate's output is high if either one of the two inputs is high. If both inputs are high, or if no inputs are high, the output is low. The XNOR gate (NOT XOR) is essentially the same except that the outputs are reversed. If either of the two inputs is high, the output will be low. If both inputs are high or if neither input is high, the output will be high.

XOR means "Exclusive OR". Exclusively, one gate is high.

The NOR gate (NOT OR) is a lot simpler. In an OR gate, if either or both gates are high, the output is high. If both gates are low, the output is low. The NOT OR function is the same except the output is reversed.

What is a gate that has to have all inputs high to be high?
What is a gate that has to have all low to be low?
Also what is Demorgan's theorem?

I know I'll be double posting but I just want to thank you for your help so far.

AND
NAND ----> XOR
De Morgan's laws - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/De_Morgan%27s_laws)

The second one must not be clear. It has to have all inputs low to have a low output.
Just in case for the first, it has to have all inputs high to have a high output.

Truth table - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Truth_table)

It says that NAND is False if both is true and true if at least one is false. I'll assume Flase is low and true is high.

Yep, NAND is wrong.

If you go to the trute table with lots of functions simultaneously on the pagem you'll find that it's either AND, OR or EXCLUSIVE OR.

If that's the ONLY condition, then XOR would be the answer.

Is flase low or high?

Actually there are two terms "Positive logic" and "Negative Logic".

Assuming this is a positive logic system LOW will be equlivelent to FALSE.

In the real world, there are concepts like open collector, open drain, wire or'ed, tri-state logic, pins are defined as inputs on power up, or defined as OFF, an input or an output on the fly.

What is use to illustrate the various input/output combinations for a logic gate?

Ps thanks for the help.

I'm going to switch gears a bit. Instead of giving you the answer, I'm giving you a link to a BCD to Decimal Decoder IC.
From the contents of the link and recent discussions, you should be able to come up with the answer.

SN74141N pdf, SN74141N description, SN74141N datasheets, SN74141N view ::: ALLDATASHEET ::: (http://pdf1.alldatasheet.com/datasheet-pdf/view/115765/TI/SN74141N.html)

What's your answer?

I'd say logic function diagram.

What is the logic circuit whose output is always the inverse of its inputs? What is inverse?

In that data sheet it may have been called a "function table", but you know it as something else. What do you know it as?

Inverse is used a lot in functions; f(x) = ; f(y) is the inverse.

In your problem "inverse" means opposite. So, what gate is the output the opposite of its input?

You must describe it in concepts that the teacher has lectured about, not what someone else calls it. Keep that in mind.

The only gates on there is And OR. AND is High inputs equal High output and OR is Low inputs equal Low output.

What's a 1 input NAND gate? They give it a special name.

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What is 25, 26 and 28?