how to set/use different versions of gcc

[Dan, Ho-Jin]

To study c++ standard library, I throwed gcc 2.95.x due to missing 
features of std::
and got gcc-cvs 3.0 branch. however, I found that gcc 3.0 is not 
maturely developed.
so, now, I want to have the both of the stable and development vesion of 
gcc.
suppose that one is configured with --prefix=/usr and the other with 
--prefix=/usr/local/
can i choose the compiler and related libraries simply evoking gcc by 
/usr/bin/gcc or /usr/local/bin/gcc??? thanks in advance.