I have been asked whether I expect you to write
two versions of "cpu.c" or only one.  Here's my
suggestion.  Use "ifdef" blocks in the "cpu.c"
code, one to compile code for the FCFS and one
to compile code for the RR code that you write.
Control which of the blocks gets compiled by
supplying the compiler with different symbols.

That way, you only need to have one file for
the code for both versions, and thus only
one set of data structures and such.  If you
do separate files, you will probably wind up
going back and forth from one to the other
correcting or improving the data structures
and the control.  You don't need that extra
headache.