$Output
(Built-in Mathematica Symbol) $Output gives the list of files and pipes to which standard output from Mathematica is sent.
$ParentProcessID gives the ID assigned to the process which invokes the Mathematica kernel by the operating system under which it is run.
$PerformanceGoal gives the default setting for the option PerformanceGoal for graphics and other algorithmic functions.
$ProcessorType is a string giving the architecture of the processor on which Mathematica is being run.
$SystemCharacterEncoding gives the default raw character encoding for the computer system on which Mathematica is being run.
$System
(Built-in Mathematica Symbol) $System is a string describing the type of computer system on which Mathematica is being run.
$Version is a string that gives the version of the Mathematica kernel you are running.
Functions for manipulating elements in explicit lists. This gives a list with x prepended. This inserts x so that it becomes element number 2.
Differentiation Total Derivatives Derivatives of Unknown Functions
"How to" Topics Building Up Calculations Lists