!TITLE IMPLEMENTATIONS

   One of the objectives of the design of ECCE is that it should not be
system-dependent, but should be implementable on a range of machines.
This video version as described in earlier sections is implemented
uniformly on EMAS 2900, VAX/VMS and the Computer Science Department's
Advanced Personal Machine.  The syntax checking capability is a
by-product of work on the programming environment for the APM.

   The detail of some features, for example those involving naming of
files, is inevitably bound up with a particular operating system.  The
performance of the editor as seen by the user is also affected by the
system, and, more especially, the mode of connection.

!<Mode of connection

   The most important factor affecting editor performance is the mode of
connection of the user's terminal.  In general, the more direct the
connection, the better the performance will be.  ECCE has a number of
options which make it possible to exercise some control over the
frequency of interaction and the volume of data transferred.

   In addition to affecting the responsiveness of the editor, an
indirect connection over the network involves an increased possibility
of unintended modification of the data stream sent to the terminal,
leading to an erroneous screen image which does not match the state of
the file.  It may also rule out the use of cursor controls and function
keys.

   If the screen image looks curious at any time, the "%D" command
should be used to re-display it.
!>
!<Network Terminal Controllers

   New software on some of the Terminal Controllers on the ERCC network
provides a much improved screen handling mode which the editor uses if
available.  On other TCPs, as an interim measure, interference with data
may be reduced by entering TCP Graph mode and input of control
characters may be enabled by entering Z mode.  With the old TCP
software, the screen image is particularly susceptible to corruption as
a result of typing ahead; this should be avoided as much as possible.

******    NB  *****
In order to permit the use of Escape sequence controls, while the editor
is being run the system Attention character is changed from Escape to
Null, which is keyed by CONTROL+@.  Any use of this Attention character
cancels video mode, so that it should be used only in extremis.
!>
!<Supported Terminals

   The list of terminals currently supported as videos in ECCE is as
follows (ERCC enumeration):

  code    terminal            highlight    part-screen scroll

   6     Perkin-Elmer Bantam      -             -
   8     DEC VT52                 -             -
  11     Visual 200            reduced         yes
  12     VT100                 reduced         yes
  13     Hazeltine Esprit      increased       yes
  15     Newbury 8000             -            yes
  20     Volker Craig 404         -             -
  21     ICL KDS7362           reduced         yes
!>
!>
!>