SIMSCRIPT II.5 Programming Language

SIMSCRIPT II.5 Programming Language
or
external processes are process name list
external processes are event name list
When an event name appears in an external process statement in the preamble, provision is made
to create a new event notice each time an input data record containing the event name is read from
the external data. This event notice is identical in form with those already described.
One of the predefined attributes in a process or event notice, eunit.a, records the unit number of
the input device on which information about this event is input. For events and processes not triggered
externally, this attribute remains zero. The logical unit numbers of devices on which external
event data are to be input are declared in a statement of the form:
or
external process units are device list
external event units are device list
The words process and event are synonymous in this case. Devices may be specified as integer
constants or as variables. If variables are used, they must be initialized to valid unit numbers before
the start of simulation. If external events have been declared but no external units statement
appears, the standard input unit is assumed to be a source of external event data. If such a statement
does appear, and the standard input unit is also to be used for event data, it must be included in the
list of external units.
A simulation program having the processes TASK and REPORT might contain the following statements
in its preamble:
external processes are TASK and REPORT
external process units are DAILY.TASKS, WEEKLY.TASKS and 5
These statements indicate that the SIMSCRIPT II.5 system must be prepared to trigger the processes
TASK and REPORT from external data, and that three input devices are to be used to input these
data. These may be indicated mnemonically as being associated with information about particular
events. However, the SIMSCRIPT II.5 system attaches no significance to these names. Any external
event may be triggered by data read from any of the declared external units.
External events and processes may be included in priority statements, declaring their priority
over other events and processes, whether internally scheduled or externally triggered. Note that the
priorities are associated with the events or processes, and not in any way with the external units.
Events or processes that are declared to be external can be given priority over other classes of
events but cannot be ranked among themselves by a break ties statement. No ranking attributes
are assigned values by external triggering, as may be done by giving arguments in a schedule statement.
Even if some instances of the event class are internally scheduled and have attributes initial-
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