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20 Cards in this Set
- Front
- Back
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Definition of file |
logical units of information created by processes |
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Define field |
basic element of data |
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Define record |
an organization of related fields treated as a unit |
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Define file |
a collection of similar records |
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Define database |
a collection of related data |
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3 fundamental types of files |
1. data 2. program 3. documents |
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types of files |
1. ordinary files 2. directory files 3. special files aka device files |
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requirements for long term information storage |
1. high capacity 2. an information must survive the termination of the process using it 3. multiple processes must be able to concurrently access the information 4. structural requirements |
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2 types of access |
1. sequential access 2. direct access aka relative access |
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file attributes |
name type location size protection time date user identification |
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Define pile |
simplest file organization - data are collected in order of arrival; the purpose is to amass data and save it |
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Define stack |
a data structure that supports insertion and remove of new data items. always LIFO. used in-store function arguments and local variables |
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Define heap |
a tree data structure on ordered data. used to refer to the memory that is available to an application and is not used for procedure call stack |
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another term for pile |
1. ordered deque 2. improved heap |
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Basic File Organization methods |
1. pile 2. sequential 3. indexed sequential 4. indexed 5. direct (hashed) |
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Define sequential |
fixed format for equi length records and key fields. very common in batch but poor for interactive applications |
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Define indexed sequential |
improved performance for interactive applications by adding an indexed file to support random access to the sequential file organization |
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Define indexed |
more flexibility than indexed sequential . it has multiple indexes reflecting each type of field that may be searched |
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Define direct (hashed) |
random access via hashing on the key value |
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Define hash function |
any algorithm that maps large data sets of variable length (keys) to a smaller sets of fixed length. |
