Page 179 - DCAP507_SYSTEM_SOFTWARE

Unit 11: Programming Languages Concept (II)

approach. On the other hand, bottom level modules provide the basic operation used by higher Notes
level modules. It is therefore important to ensure that these bottom level modules are working
correctly before these are used by other modules. This suggests that the development should
proceed in a Bottom up manner. As both issues are important in a large project, so it may be best
to follow a combination approach for such systems.
Self Assessment

Fill in the blanks:
1. A system/program is considered modular if it consists of ......................... modules so that
each modules can be separately implemented, and a change in one module has minimal
impact on other modules.

2. A set of related procedures with the data they manipulate is called a .........................
3. A ......................... approach (Pure top-down or pure bottom-up) starts by identifying the
major modules of the program.
4. A ......................... approach starts with designing the most basic or primitive module and
proceeds to higher level module that use these lower level components.

5. In practice, in large systems, a combination of two approaches is used, called as .........................
approach.

11.2 Asynchronous Operation

An asynchronous operation that utilizes the IAsyncResult design pattern is executed as two
methods named BeginOperationName and EndOperationName that start and end the
asynchronous operation OperationName correspondingly.

Example: The FileStream class offers the BeginRead and EndRead methods to
asynchronously read bytes from a file. These methods execute the asynchronous edition of the
Read method.

After calling BeginOperationName, an application can carry on implementing instructions on
the calling thread while the asynchronous operation occurs on a dissimilar thread. For every
call to BeginOperationName, the application should also call EndOperationName to obtain the
results of the operation.

Task Make distinction between BeginOperationName and EndOperationName.

11.2.1 Beginning an Asynchronous Operation

The BeginOperationName method starts asynchronous operation OperationName and returns
an object that executes the IAsyncResult interface. IAsyncResult objects accumulate information
regarding an asynchronous operation. The following table displays information regarding an
asynchronous operation.

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