Make Depend

[Gert Cuykens]

"A Makefile rule that typically scans all C/C++ source files in a
directory, and generates rules that indicate that an object file
depends on certain header files, and must be recompiled if they are
recompiled."

i dont understand this. how can a object depend on something that is
not compiled yet? Would the freebsd world not be a happier place if
make did the dependancy thingies what ever they are automatically ?