$CommandLine (Built-in Mathematica Symbol)

$CommandLine is a list of strings giving the elements of the original operating system command line with which Mathematica was invoked.

$CreationDate (Built-in Mathematica Symbol)

$CreationDate gives the date and time at which the particular release of the Mathematica kernel you are running was created.

$InstallationDirectory (Built-in Mathematica Symbol)

$InstallationDirectory gives the top-level directory in which your Mathematica installation resides.

$LicenseServer (Built-in Mathematica Symbol)

$LicenseServer is a string that gives the name of the license server that is currently authorizing Mathematica to be run.

$MachineID (Built-in Mathematica Symbol)

$MachineID is a string that gives, if possible, a unique identification code for the computer on which Mathematica is being run.

$MachineType (Built-in Mathematica Symbol)

$MachineType is a string giving the general type of computer on which Mathematica is being run.

$OperatingSystem (Built-in Mathematica Symbol)

$OperatingSystem is a string giving the type of operating system under which Mathematica is being run.

$Output (Built-in Mathematica Symbol)

$Output gives the list of files and pipes to which standard output from Mathematica is sent.

$ProcessorType (Built-in Mathematica Symbol)

$ProcessorType is a string giving the architecture of the processor on which Mathematica is being run.

$ReleaseNumber (Built-in Mathematica Symbol)

$ReleaseNumber is an integer which gives the current Mathematica kernel release number, and increases in successive releases.