iTS 1.0+)

Introduction to SCREEN COBOL

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

1-5

Pathway System Components

In a Pathway environment, the TCP executing SCREEN COBOL code at a terminal

constitutes a requester process. However, in this manual, discussions of requester-server

functions refer to a SCREEN COBOL program unit as a requester program.

Requesters

Requesters usually provide presentation services for terminal devices and communicate

with server processes. Requesters may be tasks executing SCREEN COBOL code

within a (multithreaded) terminal control process, or they may be Pathsend processes

written in Transaction Application Language (TAL), C, COBOL85, or Pascal.

Pathway/iTS requesters are written as SCREEN COBOL programs. SCREEN COBOL

programs control screen displays, manage terminals, manage messages for intelligent

devices, and perform calls to other SCREEN COBOL programs. SCREEN COBOL

programs also send data to and receive replies from Pathway server processes. A

request to a server, generated by the execution of a SCREEN COBOL SEND statement,

is managed by a terminal control process (TCP).

Requester programs may also be written as Guardian processes in the Transaction

Application Language (TAL), C, COBOL85, or Pascal. Such requester programs include

calls to the Pathsend procedures provided as part of the NonStop™ TS/MP product. For

information about writing Pathsend requesters, refer to the NonStop™ TS/MP Pathsend

and Server Programming Manual.

Servers

Servers are programs written in C, C++, COBOL85, pTAL, TAL, FORTRAN, or Pascal

in the Guardian environment to respond to requests to perform database operations. The

requests are made in the form of interprocess messages. When a SCREEN COBOL

requester program is used, these messages are generated according to the statements in

the SCREEN COBOL program and sent by a TCP. Servers receive the requests,

perform database I/O functions, and return appropriate replies to the TCP.

Figure 1-2. Multiple Terminal Control Through the TCP

002CDT .CDD

TCP

SCREEN

COBOL

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