Exchange/RJE Manual

Underlying Communications Subsystems
Introduction
104698 Tandem Computers Incorporated 1–5
Block mode contains three individual modes of operation:
block mode with 2780-blocking
block mode with 3780-blocking
block mode without blocking
Exchange/RJE typically appears to the remote system as a card reader, a printer,
or a card punch (these being the devices supported by 2780 and 3780 data
communications terminals). Exchange/RJE is not limited to these types of devices
and can use any type of device or file supported by the operating system.
All modes function the same whether you use them through the command
interpreter or programmatic interface. The only differences are the operational
differences between the command interpreter and the programmatic interface.
The Command Interpreter There are two ways you can use the Exchange/RJE command interpreter:
You can enter commands interactively through a terminal.
You can enter a sequence of commands in a command file and then have the
command interpreter execute the commands from the file.
You can combine the two methods, using a command file to perform some tasks, such
as setting up a standard configuration, and entering commands interactively to
perform other tasks, such as specifying the particular file to send or receive.
The Programmatic Interface The Exchange/RJE programmatic interface allows you to control the line server by
making standard system procedure calls. If you want to write a program that uses
Exchange/RJE, you use the programmatic interface to communicate with the line
server.
The programmatic interface provides a record-oriented interface to the line server in
which your program passes data to and receives data from the line server one record
at a time. Your program must handle the writing and reading of those records to and
from the files on the Tandem system. The line server handles only the sending and
receiving of records over the data communications line. This situation differs from
that of the command interpreter interface, where you specify operations on an entire
file at a time and the Exchange/RJE send/receive server handles the writing and
reading of records to and from the files on the Tandem system.