why .mod files differ after every time i compile a .f file

Question

I have a fortran file say abc.f.

This abc.f has some code inside and defines a module say abcd.

When i compile the file using ifort compiler it creates abcd.mod,and abc.o.

I save these .o and .mod file in another location and recompile the abc.f.

Now when i compare the new abcd.mod with old one it differs, but .o files are same.

What could be the possible reason?

Answer 1

Its a timestamp which is included in the mod files. http://en.wikipedia.org/wiki/Timestamp you can refer this for more on timestamp

Answer 2

probably timestamping. Try running strings on the .mod and checking it - mostly likely the first few lines.

Answer 3

Thanks for all your answers. Its a timestamp only which is making difference. Timestamp is stored at 49 to 52 or 49 to 56 bytes(depending on architecture) in .mod file. You can extract the remaining content using dd command for comparison.