Thanks for reading my writing in advance.

My question is what is the differece between CRC-16 and Reverse CRC-16.

I have read many paper and web regarding CRC-16 and finally understood.
(I understood CRC-algorithm thru "A tutorial on CRC" that has best
explanation about CRC)
Looking ppp source code, I met strange CRC-16 code and I got to know
that algorithm used in the code is "reverse CRC-16 algorithm".

Here is my question.

1. Anyone can explain about the 1) CRC-16 algorithm and 2) difference of above
two algorithm?

2. why PPP use reversed CRC-16?(Any special reason is there?)

3. what are the good books or web-sites for understanding reverse
CRC-16 algorithm? Please recommend good ones.
I have already surffed web site to find the good explanation or site about
reverse CRC-16 algorithm. But I couldn't find proper material.

I hope many responses will be posted.