GDSX Manual

Extended General Device Support (GDSX) Manual–134303

4-1

DEVICE^HANDLER Example,

Running and Managing

The typical purpose of a DEVICE^HANDLER is to modify the communication of each

thread between a requester and another file. The GDSX program demonstrated in this

section, called the DEVICE^HANDLER example, includes a DEVICE^HANDLER

procedure that modifies communication between multiple requesters and the terminals

to which they are mapped. Figure 4-1 shows an overview of the processing done in this

unconverted example program. $A1 and $A2 are requester processes, each of which

communicates with a terminal by way of $GDS; the DEVICE^HANDLER in $GDS

does datastream conversion on messages sent from requester to terminal.

This section of the tutorial requires three terminals, designated the TACL terminal, the

first application terminal, and the second application terminal. (If a second application

terminal is not available, you can still do most of this section’s tutorial.) It is assumed

that the terminals are accessed by means of the TERMPROCESS IOP.

Running an Application Process

In the tutorials on both the DEVICE^HANDLER example and the LINE^HANDLER

example in Sections 4 through 7, a simple unconverted TAL application is used to send

requests to the GDSX process. (FUP may also be used as a requester.) The following

exercise familiarizes you with this application so the requester’s functioning may later

be clearly distinguished from the functioning of the GDSX process.

Figure 4-1. Overview of DEVICE^HANDLER Example

Datastream

Conversion

Passthrough

$A1

Datastream

Conversion

Passthrough

$A2

CDT001

D^H Task

$GDS

$TC1

$TC2