Software Development Part 2 Flashcards

1
Q

sequential file structure

A
  • contains consecutive records and is read starting from beginning
  • typical of data on magnetic tape
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2
Q

indexed sequential file

A
  • a file with a separate index file to help locate records more quickly random file structure
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3
Q

-random file structure

A
  • allows access to any record without starting at beginning of file
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4
Q

indexing

A

a means of specifying the order of records without actually changing their physical order

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5
Q

index file (key file or keyword file)

A

ordered list of items with references to the complete record

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6
Q

key field (record index)

A

field in the record that is indexed

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7
Q

sorting routine

A
  • places data in ascending or descending numerical or alphabetical order
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8
Q

sorting routine

A
  • puts dat in order
  • -> from highest from lowest numerically
  • -> from lowest to highest numerically
  • -> alphabetically
  • -> reverse alphabetically

common methods

  • successive minima
  • bubble sort
  • insertion sort
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9
Q

successive minima

A
  • list is searched to find smallest element
  • smallest element is brought to top of list
  • process is repeated for remaining elements
  • n(n-1)/2 comparisons needed to sort n items
  • when n is large n^2/2 is sometimes used as approximation
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10
Q

bubble sort

A
  • first and second elements in list are compared
  • if first is larger, positions are switched
  • second and third elements are the compared, and so on
  • process continues till end of list is reached, constituent one pass through data
  • process repeated until one pass through the data results in no exchanges
  • so called because smaller elements “bubble” to top of list
  • on average, n^2/2 comparisons needed
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11
Q

insertion sort

A
  • elements are ordered by rewriting them in proper sequence
  • after the proper position of an element is found, all elements below that position are bumped down one places
  • the vacancy is filled by the inserted element
  • About n^2/ 2 comparisons are needed at most
  • average number of comparisons is about n^2 /4
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12
Q

linear search (sequential search)

A
  • finds an element if a group of records is randomly organized
  • at best, one comparison is required
  • at worst, n comparisons are required in a list of n elements
  • average of n/2 comparisons
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13
Q

binary search

A
  • faster than linear search if records are in ascending or descending order
  • checks middle element, then removes half of list from consideration
  • checks middle element from remainder of list, and so on
  • maximum number of required comparisons in a list of n elements is log2 (2 is subscript down) n= log n/ log 2
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14
Q

hashing function

A
  • procedure by which a numeric or nonnumeric key is converted into a record number
  • for example, may convert each customer’s name into an integer, so that records for that customer are stored at that location number
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15
Q

collision

A
  • occurs when hashing function assigns same record number to different keys
  • chaining, linear probing, and double hashing are techniques used to resolve such collisions
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16
Q

database

A
  • can be implemented as
  • indexed file
  • linked list
  • tree structure
  • records are written in and remain in order of entry
  • various methods use to locate needed records
17
Q

indexed file

A

= keeps all data in one data file

  • maintains one separate key file for each key field (may be one or more key fields)
  • searches in key file to find record number corresponding to a given piece of data
  • updates key files each time records are added to data file
18
Q

flat file

A
  • only one file (no separate index file)

- has only one key field by which records are located

19
Q

linked list

A
  • a technique for locating records in a flat file
  • each record contains pointer to next record in key sequence
  • two pointers change whenever a record is added or deleted
20
Q

binary tree structure

A
  • each record contains two pointers, to next higher and next lower record in key sequence
    -records are referred to as nodes; first record is root node
  • node above is called parent; node below is child or offspring
  • number of comparisons needed is
    1 + (log n / log 2)
21
Q

hierarchical database

A
  • contains records in an organized, structured format
  • organizes records according to one or more indexing schemes
  • each field within a record not normally directly accessible
22
Q

relational database

A
  • stores all information in the equivalent of a matrix
  • no index files, pointers, and so on needed to find, read, edit or select information
  • information can be accessed directly by referring to field name or field value
23
Q

artificial intelligence (AI)

A
  • the capacity of a machine to
  • -> absorb and organize new data
  • -> learn new concepts
  • -> reason logically
  • -> respond to inquiries
24
Q

expert systems

A
  • learn rules from sets of events that are entered whenever they occur
  • once the rules are learned, can give advice, make predictions and diagnoses, or draw conclusions
25
Q

testability

A

determines:
- ability to detect and correct errors
- verify limiting operation
- determine functionality

26
Q

software fault tolerance

A

designed into a system by

  • synchronizing operations
  • implementing checkpoints
  • logging
  • programming recovery techniques