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Undoing Previous Commands
To undo the most recent DM command you entered, specify the UNDO
command. You can also undo the previous command by pressing the
<UNDO> key.
NOTE: The UNDO command only applies to DM operations. You
cannot undo Shell commands.
The UNDO command works by compiling a history of DM operations
in input and edit pads in reverse chronological order. UNDO reverses
the effect of the most recent DM command you specified. Successive
UNDOs reverse DM commands further back in history.
To compile its history of activities, the DM uses undo buffers (one
per edit pad and one per input pad). The undo buffers are circular
lists that, when full, eliminate the oldest entries to make room for new
ones.
The DM groups entries together in sets.
For example, an S
(SUBSTITUTE) command may change five lines. While the DM
considers this to be five entries, the five entries are grouped into a
single set so that one UNDO will change all five lines back to their
original state. When a buffer becomes full, the DM erases the oldest
set of entries. This means that UNDO will never partially undo an
operation; it will either completely undo the operation or do nothing.
An undo buffer for an edit pad can hold up to 1024 entries. An undo
buffer for an input pad can hold up to 128 entries.
Updating an Edit File
To update a file that you are currently editing, specify the PW
(PAD_WRITE) command. PW is valid for edit pads only. It requires
no arguments or options.
The first time you specify PW during an editing session, the DM
writes the contents of the edit pad to the file that is being edited,
without closing the edit pad. The DM writes the previous contents
of the file to a file with the same name and the added suffix .BAK.
Subsequent PW or WC (WINDOW_CLOSE) commands rewrite the
new file and leave the .BAK version unchanged. (For more informa5-29
Editing a Pad