ComplexityFunction is an option for Simplify and other functions which gives a function to rank the complexity of different forms of an expression.
DisplayForm[expr] prints with low-level boxes inside expr shown in explicit two-dimensional or other form.
FormBox
(Built-in Mathematica Symbol) FormBox[boxes, form] is a low-level box construct which displays as boxes but specifies that rules associated with form should be used to interpret boxes on input.
StandardForm[expr] prints as the standard Mathematica two-dimensional representation of expr.
Length
(Built-in Mathematica Symbol) Length[expr] gives the number of elements in expr.
Character represents a single character in Read.
Divide
(Built-in Mathematica Symbol) x/y or Divide[x, y] is equivalent to x y^-1.
EndOfString represents the end of a string for purposes of matching in StringExpression.
FromCharacterCode[n] gives a string consisting of the character with integer code n. FromCharacterCode[{n_1, n_2, ...}] gives a string consisting of the sequence of ...
StartOfString represents the start of a string for purposes of matching in StringExpression.