System variables are special variables that are automatically and always defined. Unlike normal variables, they cannot be explicitly mapped, and their names are not case sensitive; DATE, date and Date all refer to the same system variable. They also don't have explicit date types/sizes: they are simply either numeric or string.

You may consider them equivalent to system functions, except that they don't take any arguments.

Note that while you cannot map normal variables whose names conflict with system variables, this restriction does not apply to members of defined structures. For example, even though DATE, TIME, and CMDLIN are system variables, the following structure members, despite their names, are ordinary variables unrelated to their system variable namesakes:

DEFSTRUCT ST_EXAMPLE

    MAP2 DATE,B,4          ! (not related to system variable DATE)

    MAP2 TIME,B,4          ! (not related to system variable TIME)

    MAP2 CMDLIN,S,100      ! (not related to system variable CMDLIN)

ENDSTRUCT