BCX requires that you dimension all variables - see DIM, RAW, LOCAL, GLOBAL, STATIC in the BCX Help file
You will need to change any QB code that uses reserved BCX keywords as variables, like PI, HEX, and so on.
BCX variables are case sensitive but keywords are not.
I haven't looked at all the QB source code but it's also possible that the QB code might also have variable names or
CONST names that conflict with c/c++ and Windows API names, so those might need to be tweaked also.
All in all, it's a good exercise (for you) to acquaint yourself with both languages and especially the BCX Help file.