Download 58 Building an Application

Chapter
58
Building an Application
Introduction
The Basic Idea
An application generated with the Cadvanced SDL to C Compiler can
be viewed as having three parts:
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The SDL system
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The physical environment of the system
•
The environment functions, where you connect the SDL system
with the environment of the system
In the SDL system process transitions are executed in priority order,
signals are sent from one process to another initiating new transitions,
timer signals are sent, and so on. These are examples of internal actions
that only affect the execution of the SDL system. An SDL system communicates with its environment by sending signals to the environment
and by receiving signals from the environment.
The physical environment of an application consists of an operating
system, a file system, the hardware, a network of computers, and so on.
In this world other actions than just signal sending are required. Examples of actions that an application wants to perform are:
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•
•
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To read or to write on a file
To send or receive messages over a network
To respond on interrupts
To read and to write information on hardware ports or on sockets
The environment functions are the place where the two worlds, the SDL
system and the physical environment, meet. Here signals sent from the
SDL system to the environment can induce all kinds of events in the
physical environment, and events in the environment might cause signals to be sent into the SDL system. You have to provide the environment functions, as the Cadvanced SDL to C Compiler has no knowledge of the actions that should be performed.
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Telelogic Tau 4.5 User’s Manual
July 2003