Arrays and records

Overview

One- and two-dimensional arrays indexed from zero, reading and changing items, totalling an array with a loop, record data structures and their fields, and arrays of records.

What you need to know

Answer each one before you reveal it.

Questions from this subtopic

Each one with the model answer underneath.

1. 1

   What is a data structure?

   Model answer

   A data structure is a way of organising related data so that it can be stored and used efficiently. Arrays and records are both data structures.

2. 2

   What is an array?

   Model answer

   An array holds several items of the same data type under one name. Each item is reached using its index, its position in the array.

3. 3

   In AQA pseudo-code, what is the index of the first item in an array?

   Model answer

   The first item has index 0. An array of 5 items therefore uses the indexes 0 to 4.

4. 4

   If scores ← [12, 7, 15, 9], what is scores[2]?

   Model answer

   The value of scores[2] is 15. Indexing starts at 0, so index 2 is the third item.

5. 5

   If scores ← [12, 7, 15, 9], what does LEN(scores) return?

   Model answer

   The call LEN(scores) returns 4, the number of items in the array.

6. 6

   How is one item in an array changed?

   Model answer

   An item is changed by assigning a new value to its index, as in scores[1] ← 10. The value 10 replaces whatever index 1 held before.

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