Review of strings and languages.  Closing a set of languages using some operators.  Regular languages. Examples.  BYTE, WORD32, and WORD64 as languages computers "like", and how we represent particular subsets of the integers and reals using these sets. The representation can differ substantially from the thing that is being represented. Two's complement.  IEEE Floating point standard.  Sets with operations more generally.  Relations.  Examples of relations.  Representing relations with directed graphs (although I didn't yet use that word).