$DistributedContexts (Built-in Mathematica Symbol)

$DistributedContexts is the default value of the DistributedContexts option of functions such as ParallelTable and ParallelMap.

$LibraryPath (Built-in Mathematica Symbol)

$LibraryPath gives the default list of directories to search in attempting to find a library.

$MachinePrecision (Built-in Mathematica Symbol)

$MachinePrecision gives the number of decimal digits of precision used for machine-precision numbers.

$MessageGroups (Built-in Mathematica Symbol)

$MessageGroups is the list of rules that gives named message groups used in functions like On and Quiet.

$MinMachineNumber (Built-in Mathematica Symbol)

$MinMachineNumber is the smallest positive machine-precision number that can be used on a particular computer system.

$MinPrecision (Built-in Mathematica Symbol)

$MinPrecision gives the minimum number of digits of precision to be allowed in arbitrary-precision numbers.

$ProcessorCount (Built-in Mathematica Symbol)

$ProcessorCount gives the number of processor cores available on the computer system on which Mathematica is being run.

$ScheduledTask (Built-in Mathematica Symbol)

$ScheduledTask returns the current ScheduledTaskObject.

Adding, Removing, and Modifying List ... (Mathematica Tutorial)

Functions for manipulating elements in explicit lists. This gives a list with x prepended. This inserts x so that it becomes element number 2.

Applying Functions to Lists and Other ... (Mathematica Tutorial)

In an expression like f[{a,b,c}] you are giving a list as the argument to a function. Often you need instead to apply a function directly to the elements of a list, rather ...