🚀 go-pugleaf

I'm writing a bit of code to decode attachments to emails (and news items).

What *exactly* is UUE encoding?
What's the algorithm to encode and decode data?

UUE attachments to emails seem to be of the form:

begin 644 <filename>
 <UUE data>
end

is this always the case?

I've seen two ways of including the RiscOS filetype.
One is to put after the <filename> a comma followed by the filetype number,
the other is an extra line after the "end" which is of the form:
   RiscOS filetype : FFF

Are there others?
Are there other directives which a UUE decoder should recognise.

And what is MIME? 
Where can I find the definition?
-- 
  Demo version of !Speak from:  http://www.argonet.co.uk/users/jsd
  
  Jon Duddington                jsd@argonet.co.uk
  Coventry, England.            Speech synthesis for Acorn RiscOS computers