iTS 1.0+)

Introduction to SCREEN COBOL

Compaq NonStop™ Pathway/iTS SCREEN COBOL Reference Manual—426750-001

1-7

Communication Between Processes

Inspect

Inspect is an interactive symbolic program-debugging tool that you can use to examine

and modify SCREEN COBOL programs. Inspect runs as a separate process that

communicates through the TCP with the SCREEN COBOL program running on a

Pathway/iTS terminal. By issuing commands to Inspect, you can control and modify an

executing program.

Before you can use Inspect, the PATHMON environment must be configured for

communication with Inspect. In addition, a symbol-table file generated for the program

by the SCREEN COBOL compiler must be available to the TCP.

Communication Between Processes

SCREEN COBOL programs running at terminals communicate with servers by

exchanging interprocess messages through the TCP. The TCP executes a SCREEN

COBOL SEND statement, which builds a message and specifies a server class. The

TCP obtains a link to a server class from the PATHMON process and actually sends the

message. A server replies with an interprocess message that reaches the appropriate

terminal, again through the TCP.

When a SCREEN COBOL program provides instructions to communicate with a server

in a different PATHMON environment, the program becomes location sensitive. In this

situation, the SCREEN COBOL SEND statement indicates an external server by

specifying the Guardian node name and PATHMON name for the PATHMON process

controlling the external server. An external server is one that runs under a PATHMON

environment different from that of the requesting SCREEN COBOL program.

Specifying the node name and PATHMON name makes communication possible among

multiple PATHMON environments on the same Guardian node or on different Guardian

nodes.

Figure 1-4

illustrates the communication between PATHMON environment processes

active in requester-server message exchange. The SCREEN COBOL library contains

the object code executed by the TCP.