A couple of students have written:

        Dear Prof. Patt,
          I can't tell from the sample output for PA4, is that one space after the
          period in "Invalid move. Try again." or two spaces.  Both are used, and I
          don't want to mess up the output for something like that.
          Thank you,
        <<name withheld to protect the student who does not want to mess up>>

It's only 1 space after the period, that's the way it is on the sample
output.  And, 

        dr. patt:
        i have pretty much completed my program as of now but i had one question
        regarding an input with enter. this is probably meaningless but i wasnt
        sure if you were going to test an input of enter instead of a row or
        number and if so does it matter if the "Invalid input" prompt appears on
        the next line because of the enter that was input? or should the prompt
        appear as though it was an invalid input other than enter?

        << name withheld to protect the student who has pretty  much completed it>>

Echoing the enter key is fine even though it makes
the "Invalid move ..." message appear on the next line.

Good luck to all in getting this program finished.
See you in class on Monday.

Yale Patt