UPDATE# THE APC ESCAPE SEQUENCE

The handling of the CSI ? 34 h / l escape sequences by the VT220 and VT320
terminal emulators changed between versions 3.12 and 3.13 in order to support
Hebrew VT220/320/420 terminal emulation, and because DEC software such as
DECforms expects to use these sequences to control screen-writing direction.

Old way (described on pages 180-181 of "Using MS-DOS Kermit"): CSI ? 34 h / l
invoked the TERMINALR and TERMINALS macros, if you had them defined.  This
required each Kermit user to define them, for example in their MSCUSTOM.INI
files, a big management problem for large user communities.

New way: CSI ? 34 h / l controls screen-writing direction, left-to-right or
right-to-left (for Hebrew and Arabic), as it does on real Hebrew-model VT
terminals (see Hebrew section above).

To replace the TERMINALR/TERMINALS function, MS-DOS Kermit 3.13 now supports
the Application Program Command (APC) escape sequence, which is accepted by
MS-DOS Kermit 3.13's VT emulators, VT100 and above:

  APC <string> ST

In the 7-bit environment, APC is ESC _ and ST (string terminator) is ESC \.
In the 8-bit environment, APC is decimal 159 and ST is 156 decimal.  The
<string> can be any MS-DOS Kermit command or list of commands, separated by
commas, and can be up to 1024 bytes in length.	Upon receipt of this escape
sequence, MS-DOS Kermit executes the command(s) in the string and then
automatically resumes CONNECT mode.

  NOTE: In this respect, APC differs from the old TERMINALR/TERMINALS
  mechanism, which did NOT automatically re-enter CONNECT mode.  Thus, if
  you are recycling your TERMINALR/TERMINALS macros for APC use, be sure
  to remove the ", connect" from the end of their definitions, or else you
  will have to escape back twice the next time you want the MS-Kermit> prompt.

For safety, the APC mechanism cannot be used to invoke certain MS-DOS Kermit
commands that might do damage, like deleting your files.  Included in this
category is the RUN command, which provides access to DOS and to other
applications.  This new MS-DOS Kermit command regulates the APC mechanism:

  SET TERMINAL APC { ON, OFF, UNCHECKED }

ON (the default) means that Kermit will execute only safe commands.  OFF means
Kermit will not execute any commands and will ignore APCs.  UNCHECKED means
Kermit will execute ANY commands sent via APC.	Use UNCHECKED at your own risk.

APC is much more flexible than the old TERMINALS/TERMINALR mechanism, and can
be used for any purpose at all.	 For example, it can be used to configure
MS-DOS Kermit for use with a particular host or application by sending the
appropriate list of SET commands: communication parameters like parity,
protocol parameters like packet-length and window size, key mappings, etc.

It can also be used to initiate file transfers automatically from the host
without having to escape back to MS-DOS Kermit.	 Here's an example you can use
with C-Kermit 5A.  In your C-Kermit 5A customization file (.mykermrc or
CKERMOD.INI), add commands like this:

  define autosend set delay 0, apc receive, send \%1 \%2, statistics
  define autoreceive apc {send \%1 \%2}, statistics

Try it!	 Nothing special is required on the PC side.  Note: The APC command is
new to C-Kermit 5A(189); if you have an earlier release you can define APC as
a macro:

  define apc output \27_\%1\27\92

You can set up similar procedures with IBM mainframe Kermit, e.g. in VM/CMS by
stacking commands and using XECHO to emit the escape sequences.

You can expand these commands to handle text and binary mode if you want to:

  ; Text transfers
  define tsend set del 0, set file type text, apc receive, send \%1, stat
  define treceive apc {set fil typ text, send \%1 \%2}, stat
  ;
  ; Binary transfers
  define bsend set del 0, set file type binary, apc receive, send \%1, stat
  define breceive apc {set fil typ binary, send \%1 \%2}, stat

Use your imagination, the possibilities are endless!


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