;-*-TEXT-*-  3 October 1981 Leigh Klotz.
This program is for init files of VT52 users.  It sends the "Are you a
VT52?" code to the tty, and if it receives the "Yes, I am a VT52"
response, valrets ":TCTYP VT52" and sets the ttyloc to the program's
JCL.  It will not attempt to set the tctyp or ttyloc of a software
(SUPDUP) terminal.

Simplest use:

  :VT52P

Slightly hairer use:

  :VT52P ESG

If the JCL contains a \ character, that terminates the ttyloc and
begins a valret string, which is automatically terminated with a CR.
Succesive \ characters will provide additional CRs, but also do a ^V.
Prefix them with ^W if you don't want TTY output turned on.  Sample
use:

  :VT52P ESG\:--You are at ESG--


To use VT52P as a conditional in an init file, you should have it
valret a number, which you can check with :IF later.  It does not work
to valret a :JUMP.  Since it valrets nothing if you are not on a vt52,
you need to valret something before running it.

Don't worry if you don't understand this; it's obscure.  Just
copy the following into your init file, with appropriate
changes.  It will jump to a tag called "EXIT" in your init file
if you are using a vt52.

   0
   :VT52P Your TTY location here\1
   :IF N Q
   (:JUMP EXIT
   )

If you give VT52P JCL which starts with \, the TTYLOC will be
set to nothing (i.e., :TTYLOC will be run with no JCL), but
the usual thing will happen with the characters past the \.
This is useful if you use more than one VT52.

   0
   :VT52P \1
   :IF N Q
   (:JUMP WHERE
   )