Pathway/iTS TCP and Terminal Programming Guide

Designing Your Application

Compaq NonStop™ Pathway/iTS TCP and Terminal Programming Guide—426751-001

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SCREEN COBOL Requesters

Screen programs for Pathway terminals perform a variety of front-end functions for your

Pathway application and are typically written as single-threaded programs in the

SCREEN COBOL language. This language offers a simple programming environment

and screen-management system to drive 65xx terminals and IBM 3270 terminals.

SCREEN COBOL supports both conversational mode (for either block-mode or

conversational-mode terminals) and intelligent mode (for intelligent devices and

communications lines).

When you write a screen program in SCREEN COBOL, you can take advantage of the

features of the Compaq NonStop™ Pathway/iTS TCP. As supplied by Compaq, the

TCP supports:

•

Fault tolerance

•

TMF transactions

•

Multitasking of single-threaded screen programs

•

Access to server processes with Pathway server classes

•

Unsolicited message processing (UMP)

•

System management interfaces (that is, PATHCOM or the Pathway management

programming interface)

SCREEN COBOL requester programs do not perform any file I/O operations except to

terminals and server classes. A file I/O operation to a server class, which is in the form

of a request message, is initiated by the requester program by using the SCREEN

COBOL SEND statement.

Programming Tasks

Most Pathway applications comprise five types of screen program units that are linked

by some type of calling sequence. Each program unit allows the user to perform one

specific type of action. The program unit types are:

Another type of program unit often used is a router program. This is a special type of

program used to route communication (calls) between the other program units by using a

hierarchy called flat-tree design. This design facilitates random screen manipulation by

terminal users. A flat-tree design is typically two layers deep: the first layer is the

router and the second layer consists of all the other programs.

Logon Allows users to gain access to the application

Menu Allows users to select applications or particular application functions

List-only Allows users to select line items (for instance, an inventory item and its

price) for processing

Data entry Allows users to add, delete, and update specific data

Help Assists users in responding to application screens