What do "\\.\", "\??\", "\\?\", "\\" mean?

Question

What I know is

\\.\ 

It is used when we open a device's symbolic link in user mode

\??\ 

It is used when we open a device in kernel mode

\\?\  

long file name

\\    

UNC path.

But I want to know more detail.
Could you explain more certainly about these prefixs.

Answer 1

http://msdn.microsoft.com/en-us/library/aa365247%28VS.85%29.aspx#paths

Apparently, \?? is a short form for \Global?? according to this article:

In NT naming convention, \Global?? can also be called \?? to shorten the access.

Answer 2

They are explained in the MSDN article on CreateFile.