a basic question

Hi group, 

I am new to S/MIME and MIME concepts.. I have a few very basic question..pl.
help 

1. S/MIME message is a ascii (text) message or a binary message? 
  
2. suppose i have a .gif file which i am sending as attachment of
multipart/related MIME message. the attachment file is base64
transfer-encoded...the resulting MIME message is a binary message or a text
message. can the MIME message be srored as string.

3. I have a multipart/signed message which i have signed using my private
key...the message is a binary message or text message?

thanks in advance, 

Pradeep