How to make gcc print messages during compilation.

[ssathyan@india.smartstorage.com]

I am involved in porting applications from Windows NT to Linux.
I have 3 problems
(1) How we can make gcc to print user messages during the compilation
process.
(2) Is there a way I can stop the compilation with error messages Like
#error preprocessor directive in VC++ compilers.
 (3) Is there a good book or web site which gives a good documentation of
how to use gcc. Apart from man and info.

Thank's

Sajan