mapgen - map.def problems

[E.A. Koster]

I want to use mapgen, and had allready some response to my former question, 
thanks for that ...
I tried to run some scripts, but every time I need a file called map.def
When I create such a file with e.g. vi map.def, and run make.mapdef this file
is overrulled by other information and mapgen complains about the projection

Can someone tell me how I can create a map.def - file ? Or is this file created
by some Grass-programm. I saw the man-pages, but they only tell me that I can
edit the map.def.par file (I tried), but don't tell how to create the file
map.def

thanks,
Elwin