!TITLE SPECIAL COMMANDS

   The most important Special command is the Close command "%C" which is
the normal method of closing off the edit and making permanent the
changes to the file.  If for any reason it is desired to ABANDON the
edit without giving effect to the changes, the Abandon command "%A"
should be used instead.  The variant "%Ci" is used to invoke IMP syntax
checking before finally closing the file.
See also the section on MACROS for the Special commands "%Q" (Query key
definition) and "%K" (define Key).

!<modify Environment                %E

    The Environment command "%E" switches the Editor into a mode in
 which the various options described above may be modified.  It cycles
 through the list of modifiable options displaying the current value and
 permitting an alternative value to be specifed.  The RETURN key is used
 to move on to the next in the list and colon is used to return to
 editing.  For a numeric option, a number must be typed to specify a new
 value; for a yes/no option any response other than RETURN or colon is
 sufficient to alter the setting.
!>
!<set Display size <n>              %Dn

    This command provides an alternative means of setting MINWIN,
 without entering Environment setting mode.  When used by itself,
 without <n>, it leaves MINWIN un-altered but re-writes the display.  It
 should be used if for any reason the window has been corrupted (by an
 operator message, for example).
!>
!<set Line width/Margin <n>         %Ln / %Mn

    These commands provide an alternative means of setting WIDTH and
 MARGIN.  The parameter WIDTH specifies the maximum line length to be
 used in connection with the Adjust and 'At' commands (and for failure
 conditions in the case of Insert and Join).

 The initial default value is 80.


 The parameter MARGIN specifies a left margin position, which defines
 the effective start of the line.  This determines where the file
 pointer is placed following a Move or Move back command, and is also
 relevant to the operation of the Adjust command.  WIDTH is inclusive of
 MARGIN.
!>
!<define Secondary input            %S file-name    

    As an alternative to specifying a secondary input file at the time
 of calling the Editor, a command of the form "%S" followed by a
 file-name may be given during the course of editing.  This establishes
 the named file as the secondary input and switches to it.  Any existing
 secondary file is discarded.  In some implementations, the amount of
 information which can be added from a file specified in this way may be
 limited, compared with what can be inserted when the secondary input
 file is specified at the outset.
!>
!<Get commands from file            %G file-name    

    The parameter PRE noted above permits an initial set of commands to
 be read from a file.  The %G command allows a command file to be
 nominated at any time during the course of editing, for example, to
 allow a different set of macros to be set up, or to invoke a complex
 but stereotyped sequence of editing operations.
!>
!<Put key definitions to file       %P file-name    

    This command allows all the key definitions which have been made
 since the start of the current editing session to be saved in a
 specified file for subsequent recall (as PRE or via %G).  Definitions
 of control keys are represented in a coded form, using only printing
 characters.
!>
!<Wipe record of <n> deleted lines  %W

    The fact that the Editor retains a record of all lines deleted from
 the file, against the possibility of later re-insertion, can sometimes
 be a nuisance, since lines that are definitely not wanted again may get
 in the road of those that are.  The Wipe command "%W" causes the record
 of the last <n> deleted lines to be lost so that they become
 irrevocable.

    It may be necessary to use Wipe in order to bring in a large amount
 of data for a secondary input file to replace a large chunk deleted
 from the main file.
!>
!<IMP syntax checking               %Ci or %CI

    These variants of the Close command are used to invoke a check on
 the syntax of an IMP program file before it is finally closed.  The
 first form (lower-case 'i') signifies that a return is to be made to
 the editor whenever an error is detected; the second form (upper-case
 'I') implies checking through the entire file without interaction.

    The dialect of IMP which the checker accepts is the agreed common
 subset of EMAS IMP80 and VAX/VMS IMP77.  Some, but not all, of the
 features which are peculiar to one of these dialects are also accepted,
 in general with a "Non-standard" warning.  The checker detects most of
 the faults which would be reported by the compilers, though there may
 be minor discrepancies due to organisational differences and some of
 the table limits are inevitably different.  This is a novel feature and
 feedback from users would be helpful in refining it.
!>
!>