CP6100 I/O Process Programming Manual

SECTION 1
INTRODUCTION
One of the most common traits of computer networks is diversity.
Especially in a large organization, the work of applications is
likely to be spread among computers, terminals, and communication
equipment of various manufacture. Not only are there different
kinds of equipment, but also different kinds of communication
lines, with varying configuration requirements.
The user of an application need not know that a network is
heterogeneous, that a database is distributed over processors,
computer systems, even time zones, that one transaction is local
and another remote. In the case of some popular terminals and
computers--such as IBM mainframes and 3270-series terminals, and
asynchronous terminals in general--many vendors supply high-level
access methods so that application programmers need not consider
these issues either. For example, Tandem offers AM3270, TR3271,
SNAX, and TERMINALPROCESS for communication with those devices.
Even in these simplest of circumstances, the system manager isn't
spared: the kinds of lines in use, the precise configuration,
the distribution of work and data, can affect dramatically the
cost, performance, and reliability of applications.
But often the world is much more complex. What if an application
involves a special-purpose device, or demands the use of protocol
features not supported by available access methods? There must
be means for system programmers to build new interfaces; for
Tandem NonStop Systems, CP6100 is a means.
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