It expands the symbol DVD_MAKE, so instead of trying to include the file DVD_MAKE/generic.mak, if DVD_MAKE is set to /usr/home/me/dvdstuff then it will include /usr/home/me/dvdstuff/generic.mak.
I tried to compile some file ,with gmake and compiler, when started gmake ,I get error cant't find generic.mak , generic.mak is in different branches in the SW tree.
Do you know why I get error?
I don't think I can explain why you get the error. make itself has told you why you got the error ("can't find generic.mak") and I can't think of any way to explain "can't find generic.mak" without actually saying "can't find generic.mak".
So either generic.mak isn't on your computer, or make is looking in the wrong place.
%1 is the first parameter. So for the command "dir *.txt /s", dir would see *.txt as %1 and /s as %2.
If generic.mak is in \yyyy then probably you need to set DVD_MAKE=\yyyy.