In The URScript Programming Language manual it is written:
There are also built-in variables and functions that monitor and control I/O and robot movements.
and then each chapter has its own Variables section. Most of these contains only a variable __package__ with Value: 'None', while in module motion some variables have their name and description, e.g. __package__ with Value: 'Motion' or a_joint_default with Value: 1.4. Are these the “built-in variables”? If so, how are they used?