What kind of documentation? This is a little ambiguous.
The code should be obviously written to be readable and documented according to the style popular with given language -- this usually means comments or equivalent mechanism.

Should the documentation include a mathematical proof of correctness of the program?

A dissertation about the program's design and design decisions made?

Installation instructions?

-- RadomirDopieralski, 2007-Nov-21

Yes.

-- [[YvesPiguet]], 2007-Nov-21

"Yes" as in "all of the above"? This is quite a lot of work.

-- RadomirDopieralski, 2007-Nov-21