Good evening friends,
First off I would like to take this opportunity to thank everyone who contributed to my first post "How long does it take to learn assembly and how difficult is it?"
I would like to thank cscgal, Narue, Kc0arf in particular for their help. Although most people thought it wasn't a good move to learn assembly first, in the end I decided that I'd rather get the tough tuff out of teh way first and do the slightly easier stuff later.

I just bought a new book on the "art of assembly" and learning it without anyones help. So far things have been OK but I have ran into a couple of things i don't understand. Here is a text that I found difficult understanding:

The Hexadecimal Numbering System
Now I do know the hexidecimal system is 0-9 and letters A-F, F=15. So how on earth does 10h=16, and how do the numbers move up after 10h.

Truth gates
Here is a piece of text from the book.

"For example, if you have an eight-bit binary value 'X' and you want to guarantee that bits four through seven contain zeros, you could logically AND the value 'X' with the binary value 0000 1111. This bitwise logical AND operation would force the H.O. four bits to zero and pass the L.O. four bits of 'X' through unchanged. So does this mean that if the H.O.(high order value) was 1010 and you use the AND instruction the comuputer will turn 1010 into 0000, also does the AND instruction always turn 1's into zeros?

Signed and Unsigned Numbers
This is the one that really through me especially when the book says:
"8000h is negative because the H.O. bit is one or 100h is positive because the H.O. bit is zero.

I will be eternally greatful if someone could help me understand these basic concepts so I can continue.