Mathematica has lots of Forms. Some of those appear in
CForm and so on, but some Forms do not, like
What distinguishes when something goes into
$PrintForms and what doesn't?
Edit: As noted in the comment, https://mathematica.stackexchange.com/a/73539/1871 mentions there is also
$OutputForms which seems to include more things than
$Printforms. In particular it contains
ScientificForm, but not
What is the difference between these
It is important to understand that in a typical Wolfram Language session
Out[n]record only the underlying expressions that are processed, not the textual representations that happen to be used for their input or output.
If you explicitly request a particular kind of output, say by using TraditionalForm[expr], then what you get will be labeled with
Out[n]//TraditionalForm. This indicates that what you are seeing is
expr//TraditionalForm, even though the value of
Out[n]itself is just expr.
I note that
HornerForm do not work that way though. Is there guide to understanding what will be marked
Out[n]//XXXForm and what won't?
More generally, are there natural classes of forms? Two kinds suggested above are: those that are in
$OutputForms, those that appear as
//XXForm in output, and others.
However these might be quirky and there might be other more natural classifications of Form functions.