path to headers and libs under Linux

[Dave and Kim Nulton]

I just downloaded the FFTW package and set it up on my linux box.  I
installed it in /usr/fftw and have just began fiddling to see how it works.
I have a minor problem.  When I compile I get the error "fftw.h file not
found".  How do I tell Linux / gcc where my new library and header files
reside?  Is there an environment variable that I can set so gcc will know
where to look?

-dnult