password character class definitions

[Tim Metz]

Greetings,

As I understand it, MIT Kerberos provides for the following password 
metrics:

(1) The length of the password
(2) The number of character classes it contains, where available 
character classes are
- Lowercase letters
- Uppercase letters
- Numbers
- Punctuation
- Other Characters

I'm interested in exactly what characters comprise the Punctuation and 
Other Characters classes.

I would assume the the Punctuation class is explicitly defined in a 
source file, though I haven't had any luck tracking down which source file.
Is this accurate? and if so, which source file?

Is the Other Characters class also explicitly defined?  or is it just 
any character that is not included in one of the other four classes?
If the latter, is there any restriction on what characters can/cannot be 
included in a password?

The underlying question I'm looking into is "Which special characters 
are allowed in passwords?

Thanks,

  - Tim Metz