LaTeX allocates
- 56
\count registers
- 92
\dimen registers
- 31
\skip registers
- 16
\box registers
- 4
\toks registers
Running a document with the report class allocates another
- 9
\count registers
- 1
\dimen register
- 2
\skip registers
Several of these parameters are for internal usage. If we exclude parameters with @ in their name, we get
\count registers
\interfootnotelinepenalty
\interdisplaylinepenalty
\dimen registers
\maxdimen
\normallineskiplimit
\jot
\leftmargin
\rightmargin
\listparindent
\itemindent
\labelwidth
\labelsep
\linewidth
\leftmargini
\leftmarginii
\leftmarginiii
\leftmarginiv
\leftmarginv
\leftmarginvi
\fboxrule
\fboxsep
\tabbingsep
\arraycolsep
\tabcolsep
\arrayrulewidth
\doublerulesep
\unitlength
\footnotesep
\topmargin
\oddsidemargin
\evensidemargin
\headheight
\headsep
\footskip
\textheight
\textwidth
\columnwidth
\columnsep
\columnseprule
\marginparwidth
\marginparsep
\marginparpush
\paperheight
\paperwidth
\skip registers
\hideskip
\normalbaselineskip
\normallineskip
\smallskipamount
\medskipamount
\bigskipamount
\fill
\topsep
\partopsep
\itemsep
\parsep
\floatsep
\textfloatsep
\intextsep
\dblfloatsep
\dbltextfloatsep
The report class adds
\bibindent (a \dimen)
\abovecaptionskip (a \skip)
\belowcaptionskip (a \skip)
Packages will add many more.
There are also all the internal parameters of TeX that will have a default value (see List of TeX internal parameters? for a partial list, but you should consult the big manuals, either the TeXbook or TeX by topic).
All these (with the exception of box registers) can be looked at with \the.
There are also “pseudovariables”, that is, parameterless macros which hold a value. Among them
\baselinestretch
\arraystretch
and some more. These can be looked at with \meaning.
\let- approach in order to store the old definition in order to be able to restore it later on – Apr 23 '17 at 10:51\baselinestretchmacro expands to1for example (by default from LaTeX core). (Looking intolatex.ltxprovides some clue). Classes and packages might change this value, of course – Apr 23 '17 at 10:53