FullForm[expr] prints as the full form of expr, with no special syntax.
Example: FullForm[a + b^2] .
FullForm acts as a "wrapper", which affects printing, but not evaluation.
FullForm always effectively uses "PrintableASCII" as the setting for $CharacterEncoding.
See Section 2.1.1, Section 2.1.1, Section 2.1.4, Section 2.3.1, Section 2.3.13 and Section 2.9.1.
See also: InputForm, TreeForm.
New in Version 1; modified in 5.0.