About *.dsp, *.cpp, *.gdf files question

Dear Experts,

I am quite novice here about Altera's h/w and s/w range.

I need some info on my current working project. I got some files which have *.dsp, *.CPP, *.POF, *.gdf extension and I can see some of these files on notepad. but still curious what are these files and through which software I can review the codes.

Now by using Quartus 9.1 I opened *.gdf file which shown me some logical algorithm of some blocks and chips.

With same project there is a file with *.CPP extension. which I believe C programing but I dont understand how this file works with Altera's controller boards.

Also I have three *.DSP files I can see some codes by opening them by notepad but still dont understand how it relates and its significance with h/w and s/w flow.

Please guide me. I am attaching some dsp and cpp files with this thread.

Regards