[Cryptography] What is the difference between a code and a cipher?

[John Levine]

In article <5407D980.1010707 at zen.co.uk> you write:
>Old chestnut - is it being intended to be hard to decrypt? Having a 
>variable key? Something else?
>
>I don't know whether there is a definitive answer, but opinions are sought.

Of course there's no definitive answer.

My approximate understanding is that ciphers deal with chunks of data
of a mechanically determined size, such as one or two characters, or
32 bits.  Codes deal with semantically sized chunks of data, typically
words in a natural language.

There has always been a lot of overlap.  The famous Zimmerman
Telegram, for example used a code that represented German words as
numbers, but they had to encipher ARIZONA as letter pairs because it
wasn't in the code book.  (Oddly, TEXAS was.)

R's,
John