AlgorithmsTopic Summary
Knowledge Organiser: Arrays and Records
Part of Insertion Sort · GCSE GCSE Computer Science revision
This topic summary covers Knowledge Organiser: Arrays and Records within Insertion Sort for GCSE Computer Science. Revise Insertion Sort in Algorithms for GCSE Computer Science with 15 exam-style questions and 10 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 8 of 8 in this topic. Use this topic summary to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 8 of 8
Practice
15 questions
Recall
10 flashcards
Knowledge Organiser: Arrays and Records
Key Terms
- Array: A collection of elements of the same data type stored under one variable name
- Index: The position number used to access an element in an array (starts at 0)
- 1D array: A single row of elements accessed by one index
- 2D array: A grid of elements accessed by row and column indices
- Record: A data structure that groups related fields of different data types together
- Field: A named piece of data within a record (e.g. name, age, score)
Must-Know Facts
- Arrays are zero-indexed: the first element is at index 0, last is at index length-1
- All elements in an array must be the same data type
- 2D arrays use [row, column] notation — row first
- Records can store different data types in the same structure
- Record fields are accessed using dot notation:
student1.name - Accessing index 10 in an array of 10 elements causes an error (valid: 0–9)
Key Concepts
- Declare 1D array:
array scores[10] - Access element:
scores[0] = 85 - Declare 2D array:
array grid[3, 4] - Access 2D element:
grid[1, 2] = "X" - Define record:
record Student ... name: String ... endrecord - Use dot notation:
student1.age = 16
Common Mistakes
- Using 1-based indexing: Arrays are 0-indexed — the first element is at index 0, not 1; the last element in an array of size 10 is at index 9, not 10
- Accessing an out-of-bounds index: Accessing
scores[10]in an array declared asarray scores[10]causes a runtime error — valid indices are 0 to 9 - Storing mixed data types in an array: All elements in an array must be the same data type — use a record if you need to group different types together
- Confusing arrays and records: Arrays store multiple values of the SAME type; records group related fields of DIFFERENT types (e.g. name as string and age as integer)
- Getting 2D array notation wrong: 2D arrays use [row, column] — row index comes first;
grid[2, 3]means row 2, column 3
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