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Data Structures

Arrays of records

  • 3 things to know
  • AS Unit 1

Overview

Array of records, how the record with a given membership number is found and how records meeting a condition are counted.

What you need to know

Answer each one before you reveal it.

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Key term

Describe how the record with a given membership number is found in an array of records

Key term

In what way does an array of records resemble a file of records?

Key term

Why is a two-dimensional array a poor substitute for an array of records?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What is an array of records?

    Model answer

    It is an array in which every element is a complete record, giving a table where each element is one entity and each field of the record is a column of that table.

  2. 2

    How is a single field of one element of an array of records referred to?

    Model answer

    The array is indexed first and the field then named, as in members[3].surname.

  3. 3

    Write pseudocode to output the surname of every member in an array of 100 member records.

    Model answer

    FOR i FROM 0 TO 99, OUTPUT members[i].surname, END FOR.

  4. 4

    Describe how the record with a given membership number is found.

    Model answer

    A loop runs through the elements in use comparing the membership field with the target, stops and reports the index as soon as they match, and reports that it is absent if the loop finishes without a match.

  5. 5

    How is a field of one record in the array updated?

    Model answer

    By assigning to that field of the indexed element, as in setting members[7].balance to members[7].balance − 5.

  6. 6

    Describe how records meeting a condition are counted.

    Model answer

    A counter is set to zero and a loop tests the relevant field of every element in use, adding one to the counter each time the test succeeds.

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