User`s guide

System Control Functions
The functions listed in the following table return information about the system and system
parameters.
Keyword Function
CAS This function compares a real variable to a test value, and
conditionally sets a new value as one indivisible operation.
DEFINED Determine whether a variable has been defined.
ERROR Return the error number of a recent error that caused program
execution to stop or caused a REACTE reaction.
$ERROR Return the error message associated with the given error code.
FREE Return the amount of unused free memory storage space.
GET.EVENT Return events that are set for the specified task.
ID Return values that identify the configuration of the current system.
$ID Return the system creation date and edit/revision information.
INTB Return the value of two bytes of a string interpreted as a signed 16-
bit binary integer.
LAST Return the highest index used for an array (dimension).
PARAMETER Return the current setting of the named system parameter.
PRIORITY Return the current reaction lock-out priority for the program.
SELECT Return the unit number that is currently selected by the current task
for the device named.
STATUS Return status information for an application program.
SWITCH Return an indication of the setting of a system switch.
TAS Return the current value of a real-valued variable and assign it a new
value. The two actions are done indivisibly so no other program task
System Control Functions
System Control Functions
V+Language User's Guide, v17.0
Page 150