Are you looking for a simple way to see a GUI program on your system? These files give you that opportunity without the need to download and install the entire compiler. Please use the basic procedures on the "Hello World" page to compile and run the programs.
If you get the error message "cannot find -lx11" when compiling then you should probably install the libx11-dev package. If you plan to use fpGUI later then you can install the libxft-dev package instead because that package includes libx11-dev.
If you get the error message "cannot find -lc" when compiling on i386 Linux then you should probably install the libc-dev package.
Contact information on home page