Pathway/iTS TCP and Terminal Programming Guide

Programming for Specific Terminals
Compaq NonStop™ Pathway/iTS TCP and Terminal Programming Guide—426751-001
3-14
Using Conversational Terminals
Given the screen size definition, the TCP searches a screen mode definition table to find
the first appropriate base size. The table search occurs in the order that the modes are
listed. Therefore, you must ensure that the screen size specified results in the desired
screen mode being selected. For example, if you want the 66-column mode, you must
specify a width between 41 and 66 to prevent the 40-column mode from being used.
If no screen size is specified in the base screen definition, the 80-column mode (24,80)
is used.
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 screens.
Using Conversational Terminals
A conversational terminal is any terminal that the file system recognizes as operating in
conversational mode. A conversational terminal processes carriage return, line feed, and
bell operations. If the data entered during ACCEPT processing exceeds the size of the
I/O buffer, the terminal simply redisplays a field prompt without an advisory error
message.
Some of the SCREEN COBOL statements and clauses act differently in block mode
than in conversational mode. This discussion summarizes information about using
conversational mode.
Conversational-Mode Program
A SCREEN COBOL program written for conversational-mode operation can run on
either a block-mode terminal or a conversational-mode terminal. When a program is
specified as conversational, that program performs according to the restrictions for a
conversational terminal regardless of the type of terminal on which the program runs.
A SCREEN COBOL program running in conversational mode performs as follows:
•
Displays information on the terminal during an ACCEPT statement, one line at a
time
•
Accepts data entered from the terminal one line at a time
Table 3-5. Screen Modes for 6540 Personal Computers
Base Screen Size
Mode Lines Columns
40-column (80-column screen with double-wide characters) 1-24 1-40
66-column (132-column screen with double-wide characters) 1-27 1-66
80-column (80-column screen with standard characters) 1-24 67-80
132-column (132-column screen with standard characters) 1-27 67-132