Pathway/iTS TCP and Terminal Programming Guide

Programming for Specific Terminals
Compaq NonStop™ Pathway/iTS TCP and Terminal Programming Guide—426751-001
3-2
Controlling the Screen Modes
When running a SCREEN COBOL application on the IBM terminals, consider the
following:
•
A single screen definition can be displayed successfully on any model as long as its
logical screen size is less than or equal to the maximum physical screen size
capability of the terminal. If the logical screen size is greater than the maximum
physical screen size, the terminal suspends operation with the following error:
ERROR - *3990* REFERENCED SCREEN IS ILLEGAL FOR TERMINAL
TYPE
•
A single field that wraps from one line to the next in the logical screen definition
does not wrap, or wraps differently, if the physical screen width exceeds the logical
screen width. The field wraps around to the next line only at the end of the physical
line. This wrapping is an important consideration if a screen is intended to run on
both 40-column displays and 80-column displays.
Controlling the Screen Modes
As shown in Table 3-1, some IBM terminals have alternate screen sizes. The logical
screen size specified in the SCREEN COBOL screen definition of the current base
screen determines which mode the terminal operates in.
For example, terminal model IBM 3278 M5 has these two screen modes:
When a SCREEN COBOL application is run on the IBM 3278 M5 terminal, the screen
mode is determined as follows:
•
If the screen size definition is equal to or less than the line limit of 24 and the
column limit of 80, the 80-column mode is used.
•
If the screen size definition is in the line range of 25 through 27, or in the column
range of 81 through 132, the 132-column mode is used.
•
If no screen size is specified, the 80-column mode is used.
Base Screen Size
Mode Lines Columns
80-column (80-column screen with standard characters) 1-24 1-80
132-column (132-column screen with compressed characters) 1-27 1-132
Note. Switching screen modes can decrease performance because the terminal memory
is cleared to spaces on every mode switch. For the best performance for your SCREEN
COBOL application, use the same screen mode for all the screens.