FTN \ contents.txt  

                     
directory FTN contains one zip file:

dirdif.zip    [ unzip generates 4 files: ]

For handling simplicity the FORTRAN file 
has been split into four parts, which can be compiled
individually; these files are the result of unzip: 

dirdif1.f   
dirdif2.f   
dirdif3.f   
dirdif4.f   

dirdif1.f +dirdif2.f +dirdif3.f +dirdif4.f = dirdif.f

=============================================================
note:  the file dirdif.f is also given in directory  unix/FTN