Makefile and LInkdef.h

I’m following a tutorial for the analysis of ATLAS Dataset,
it has a makefile and linkdef.h file,
it was working fine when I had only one class(eventloop.cpp and eventloop.h)
when I added another class I’m unable to add it properly
also the ttorial says if you have to add more than one header file, then mention it on second line add backslash after each line.

this makefile was working fine but now I have to add data.h and data.o

Can you point where this example is ?

Thankyou for your response, but I’ve solved the issue.
it was a minor issue within the code