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$ProcessorTypeHeldPart

$HistoryLength

FilledSmallSquare$HistoryLength specifies the number of previous lines of input and output to keep in a Mathematica session.

FilledSmallSquare The default setting for $HistoryLength is Infinity.

FilledSmallSquare Values of In[n] and Out[n] corresponding to lines before those kept are explicitly cleared.

FilledSmallSquare Using smaller values of $HistoryLength can save substantial amounts of memory in a Mathematica session.

FilledSmallSquare See The Mathematica Book: Section 2.13.1.

FilledSmallSquare See also: $Line.

$ProcessorTypeHeldPart