ACC Programmer's Reference Guide

Chapter 1 17
ZCOM Subsystem
ZCOM Concepts
ZCOM Concepts
Throughout this manual, references are made to terminal ZLU or just
terminal. This does not mean a physical terminal device type but is a
generic term that can refer to any kind of physical or logical entity.
Examples of physical entities are printers, an HDLC link, terminals, etc.
Examples of logical entities might be an X.25 Permanent or Switched
Virtual Circuit.
In the ZCOM Subsystem, messages are sent directly from sender to
receiver (where the receiver is another program or a terminal ZL U).
They are routed using a pointer called a ‘ZLU’ which stands for ‘ZCOM
Logical Unit’. ZCOM uses the ZLU for its addressing mechanism. A ZLU
may represent a terminal (for instance, an X.25 virtual circuit) or an
application program. Messages are sent to and received by ZLUs.
Figure 1-3 on page 18
shows a sample set of program and terminal ZLUs,
and their interaction with each other and a Mux card: