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Ch2 Data Organization and Data Control, (Filter
allows users to specify a…
Ch2 Data Organization and Data Control
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2.2 Data Control
Data Vaidation(Checking)
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Format check
~the form of data follows
some known pattern(e.g.MC, CheckBox,
drop down mean)
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Check digit
~used for self-checking ,parity check is a common
application of check digit (e.g.1100 0011)
(e.g.ISBN)
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2.3 Data Hierarchy
Field
~represent a specific fact of a record
~can be of type:numeric, text, data, Boolean
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2.5 File Access Modes
Sequential Access Mode
-Thenseek time is long and unpredictable when record are retrieved randomly
-E.g. a magnetic tape
Direct Access Mode
-high relatability, speed and capacity
-E.g. hard disk
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Data Entry Forms
-provide a user -friendly environment for data entry
-perform data validation such as range check
-perform data verification
-simplify data entry with features
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