Pathway/iTS TCP and Terminal Programming Guide

Programming for Specific Terminals

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

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Internal Function-Key Queuing

6530 terminals have the unique capability of internally queuing a function key without a

read operation being posted. When no terminal read operation is in progress and a

terminal key is pressed, the function key value is stored inside the terminal. The value is

read upon the next ACCEPT statement that the SCREEN COBOL program executes.

This terminal feature provides a significant convenience for most Pathway applications.

You might, however, write an application that uses ESCAPE clauses in which this

terminal feature is inappropriate.

In this situation, a function key is queued during the interval between the cancellation of

one read and the arrival of another read so that the function key intended for the first

operation is in fact applied to the second operation. The terminal operator cannot tell

that the first read has been canceled; when the operator presses the function key

intending to execute that original action, the key is automatically queued and executed at

the next read.

Your program can avoid this situation by causing the keyboard to lock after the

cancellation of a read in the following cases:

•

After the ESCAPE ON UNSOLICITED MESSAGE clause

•

After the ESCAPE ON TIMEOUT clause

The Compaq NonStop™ Pathway/iTS SCREEN COBOL Reference Manual describes

the following two SCREEN COBOL special registers that control locking the keyboard

when an ESCAPE operation has been performed:

•

PW-QUEUE-FKEY-UMP

•

PW-QUEUE-FKEY-TIMEOUT

Using EM6530PC on a 6540 Personal Computer

The 6540 personal computer (PC) was originally equipped with the terminal emulator

EM6530PC. EM6530PC emulates the capabilities of the 6530 terminal. The

EM6530PC terminal emulator is upwardly compatible with the 6520 and 6530

terminals. Program units compiled for a 6520 or 6530 terminal run successfully with

EM6530PC.

The following differences exist between the 6530 terminal and the EM6530PC

emulator:

•

The EM6530PC emulator does not support alternate input devices; the 6530

terminal does support them.

•

The EM6530PC emulator has more screen modes than the 6530 terminal.

The EM6530PC emulator has four screen modes, as shown in Table 3-5

. The logical

screen size specified in the SCREEN COBOL screen definition of the current base

screen determines which mode the terminal operates in.