How can I leave telnet temporarily?

[Xiao-He Zhang]

   Sorry if this has been discussed recently.  Can anyone tell me how I can
escape back to local host from "telnet" temporarily  and how I can supply a
login file for "telnet"?  More specificly,
  1.  I see a "z" in telnet commands and it returns me back to my local host.
If I am using a Unix machine, "fg" gets me back to telnet prompt.  But I don't
know how to reconnect to the remote machine except logout the remote machine
and login again.  Is there any way to reconnect me back to the remote machine
without logout first?  If I am using a VMS machine, I even don't know how to
resume the telnet process.
  2.  To log in to a remote machine using telnet, I must say who I am, my
password (of course) and the terminal type.  Is it possible to put these
information in a login file and automate the login procedure so that the first
thing I'll see is the shell prompt of the remote machine?  Better yet, can
I use a crypted file to protect my password in other systems?

   Thank you in advance.

xiao-He Zhang || xiaohe at tybalt.caltech.edu  |  xiaohe at caltech.bitnet