Page 188 - DCAP507_SYSTEM_SOFTWARE

System Software

Notes 11.4 Summary

 A system/program is considered modular if it consists of direct modules so that each
modules can be separately implemented, and a change in one module has minimal impact
on other modules.
 To produce modular design, some criteria must be used to select modules so that the
module support well defined abstractions and are solvable and modifiable separately.
 A top-down design approach starts by identifying the major modules of the program i.e.
decomposing them into their lower level modules and iterating until the desired level of
details is achieved.
 A bottom-up design approach starts with designing the most basic or primitive module
and proceeds to higher level module that use these lower level components.
 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.
 If an application cannot execute any additional work until it obtains the results of the
asynchronous operation, the application must block until the results are obtainable.
 An asynchronous operation is initiated by a function that is named with the prefix async_.
These functions will be pointed to as initiating functions.
 In real meaning multitasking is simple, even though we have to be enormously cautious
when implementing it.

11.5 Keywords

Asynchronous Operation: Asynchronous operation is initiated by a function that is named with
the prefix async_. These functions will be pointed to as initiating functions.
Bottom-up Approach: A bottom up design approach starts with designing the most basic or
primitive module and proceeds to higher level module that use these lower level components.
Top-down Approach: A top down design approach starts by identifying the major modules of
the program i.e. decomposing them into their lower level modules and iterating until the
desired level of details is achieved.

11.6 Review Questions

1. What is functional module? When a system/program is considered as modular? Illustrate.
2. Enlighten the advantages of Modular Approach.

3. Make distinction between Top-down approach and Bottom-up approach.
4. What are the methods that start and end the asynchronous operation? Discuss.
5. Illustrate the concept of beginning an Asynchronous Operation with example.

6. Elucidate the process of ending an Asynchronous Operation.
7. Depict the various conditions used in asynchronous operations.
8. Explain how to execute multitasking.

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