Very basic questions but hard to find in google!

`return sqrt(eps - 2.*log(eps + rand()/(double) RAND_MAX))*cos(rand()*pi2/RAND_MAX);`

The part of the formula where it says "2.*log". I belive the "dot" only represnts that the number 2 is 2.0. However, I am not 100% sure about this as I actually dont see the reason to put "2." instead of just "2" So, does the "dot" indicate 2.0 or does it represent something else?

Second basic question:

`aux += ((K-Sp)>0?K-Sp:0)`

What does the "?" mean and what does the ":" mean.

Thanks alot

YR