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12:
the TransactionProcessor.theTransaction.TransID, _
13: theTransactionProcessor.theTransaction.DateTimeStamp
14: End If
15: Exit Sub
16: withdrawErr:
17: Call RaiseError(MyUnhandledError, WithdrawFunds:withdraw
Method)
18: End Sub |
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This chapter presented you with an overview of the File Operations Subsystem. In particular, you learned the purpose of this subsystem, including helpful treatment of the random, sequential, and binary file access mechanisms, as well as how to use the power of the Rich Text Box versus older file access methods. You also were presented with the classes in the subsystem, as well as their methods and properties, arguments, and returns. Notable classes introduced to you included RandomFile, SequentialFile, BinaryFile, IPersistence, IFileSubsystem, and RichTextFile. You also received practical guidelines for implementing the File Operations Subsystem, as well as how to incorporate the subsystem into the Samsona Bank Teller System example. |
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Q What kinds of information are both the random file access and binary file access mechanisms good for? |
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A They are both good for record-oriented information. |
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A Padding is the inserting of blank spaces to a string variable value. |
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Q What happens when you try to add more bytes to a random access file column than Visual Basic expects? |
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A An error occurs. Before opening a random access file for output, try to implement code to enforce the lengths of columns. |
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Q In opening a sequential access file, what is the purpose of the Append Keyword? |
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A The Append keyword alerts Visual Basic that the application will add additional data to a file that already contains information. |
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