This is documentation for Mathematica 5, which was
based on an earlier version of the Wolfram Language.
View current documentation (Version 11.2)

Documentation / Mathematica / Built-in Functions / System Interface / Mathematica Sessions /

$Pre

FilledSmallSquare $Pre is a global variable whose value, if set, is applied to every input expression.

FilledSmallSquare Unless $Pre is assigned to be a function which holds its arguments unevaluated, input expressions will be evaluated before $Pre is applied, so the effect of $Pre will be the same as $Post.

FilledSmallSquare $Pre is applied to expressions, while $PreRead is applied to strings which have not yet been parsed into expressions.

FilledSmallSquare See Section 2.14.1.

FilledSmallSquare See also: $Post.

FilledSmallSquare New in Version 1.

Further Examples