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Previous: <a rel="previous" accesskey="p" href="UndelLine.html#UndelLine">UndelLine</a>,
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<h4 class="subsection">4.7.4 DoUndo</h4>
<p><a name="index-DoUndo-126"></a>
Syntax: <code>DoUndo [0|1]</code><br>
Abbreviation: <code>DU</code>
<p class="noindent">sets the flag that enables or disables the undo system. When you turn
the undo system off, all the recorded actions are discarded, and the undo
buffers are reset.
<p>If you invoke <code>DoUndo</code> with no arguments, it will toggle the flag. If you
specify 0 or 1, the flag will be set to false or true, respectively. A lower
case ‘<samp><span class="samp">u</span></samp>’ will appear on the status bar if the flag is true.
<p>The usefulness of this option relies in the fact that the undo system is a major
memory eater. If you plan to do massive editing (say, cutting and pasting
megabytes of text) it is a good idea to disable the undo system, both for
improving (doubling) performance and for using less (half) memory. Except for
this, on a virtual memory system we see no reason to not keep the undo flag
always true, and this is indeed the default.
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