$SharedFunctions (Built-in Mathematica Symbol)

$SharedFunctions is the list of functions currently being shared among parallel kernels.

$SharedVariables (Built-in Mathematica Symbol)

$SharedVariables is the list of variables currently being shared among parallel kernels.

$SoundDisplayFunction (Built-in Mathematica Symbol)

$SoundDisplayFunction gives the default setting for the option DisplayFunction in sound functions.

$SyntaxHandler (Built-in Mathematica Symbol)

$SyntaxHandler is a global variable which, if set, is applied to any input string that is found to contain a syntax error.

$SystemCharacterEncoding (Built-in Mathematica Symbol)

$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.

$SystemWordLength (Built-in Mathematica Symbol)

$SystemWordLength gives the effective number of bits in raw machine words on the computer system where Mathematica is running.

$UserName (Built-in Mathematica Symbol)

$UserName gives the login name of the user who invoked the Mathematica kernel, as recorded by the operating system.

$VersionNumber (Built-in Mathematica Symbol)

$VersionNumber is a real number which gives the current Mathematica kernel version number, and increases in successive versions.

Algebraic Manipulation (Mathematica Overview)

Structural Operations on Polynomials Finding the Structure of a Polynomial Polynomial Orderings