As a addendum to Percy's excellent post:
1) Hamming codes are fascinating. Lots of links can be found by typing "hamming code" into Google or Yahoo. (I can't remember for sure, but I think the little "bar code" under the address on commercially-posted U.S. envelopes is a Hamming or related code.)
2) Ditto Huffman codes.
3) Look also the work of Agner Krarup Erlang.
4) Read about the development of facsimile systems (i.e. FAX machines).
-Neil (Who's done embedded SW engineering on Telco and FAX R&D projects -- and lived to tell about it!)
[This message has been edited by NeilUnreal, 07-15-2003]