Arrays (Cambridge International IGCSE Computer Science)

Exam board Cambridge International · IGCSEUpdated 2026-02-12

1-Dimensional Arrays

Spec point — "1 Declare and use one-dimensional (1D) and two-dimensional (2D) arrays 2 Understand the use of arrays 3 Write values into and read values from an array using iteration"

1-Dimensional Arrays

What is an array?

An array is an ordered, **static set of elements **in a fixed-size memory location
An array can only store** 1 data type**
A 1D array is a linear array
In languages such as Python, indexes start at 0, known as zero-indexed
In CIE pseudocode, index's start at 1

1d-array-example

Concept	Pseudocode	Python
Create	`DECLARE scores: ARRAY[1:5]OF INTEGER`	`scores = []`
Creates a blank array with 5 elements (1-5)	Creates a blank array
`scores ← [12, 10, 5, 2, 8]`	`scores = [12, 10, 5, 2, 8]`
Creates an array called scores with values assigned
Assignment	`colours[4] ← "Red"`	`colours[4] = "Red"`
Assigns the colour "Red" to index 4 (4th element)	Assigns the colour "Red" to index 4 (5th element)

Examples

Creating a one-dimensional array called ‘array’ which contains 5 integers.

Create the array with the following syntax:

Pseudocode	Python
`DECLARE MyArray : ARRAY[1:5] OF INTEGER`	`array = [1, 2, 3, 4, 5]`

Access the individual elements of the array by using the following syntax:

Pseudocode	Python
`MyArray[1] ← 1`	`array[index]`

Modify the individual elements by assigning new values to specific indexes using the following syntax:

Pseudocode	Python
`MyArray[index] ← newValue`	`array[index] = newValue`

Use the len function to determine the length of the array by using the following syntax:

Pseudocode	Python
There is no built-in length function in CIE pseudocode. The array length is known from the declaration or stored in a variable.	`len(array)`

In the example the array has been iterated through to output each element within the array
A for loop has been used for this

Pseudocode

Python

2-Dimensional Arrays

Spec point — "1 Declare and use one-dimensional (1D) and two-dimensional (2D) arrays 2 Understand the use of arrays 3 Write values into and read values from an array using iteration"

2-Dimensional Arrays

What is a 2-dimensional array?

A 2D array extends the concept on a 1D array by adding another dimension
A 2D array can be visualised as a table with rows and columns
When navigating through a 2D array you first have to go down the rows and then across the columns to find a position within the array

2d-array-example

Concept	Pseudocode	Python
Create	Declare a 2D array with name and number for 3 people	Creates a 3x2 blank array (3 people, each with name and number)
`DECLARE NamesAndNumbers : ARRAY[1:3, 1:2] OF STRING` `1:3` = 3 rows → one for each person `1:2` = 2 columns → one for name, one for number `OF STRING` → both names and phone numbers are stored as strings	`NamesANDNumbers = [[None, None], [None, None], [None, None]]`
Declare a 2D array called`players`with`name` and`score`assigned for 4 people (Alice, Bob, Charlie & Daisy)
`// Declare a 2D array with 4 rows and 2 columns (name and score)` `DECLARE players : ARRAY[1:4, 1:2] OF STRING` `// Assign values to each player` `players[1,1] ← "Alice"` `players[1,2] ← "25"` `players[2,1] ← "Bob"` `players[2,2] ← "30"` `players[3,1] ← "Charlie"` `players[3,2] ← "22"` `players[4,1] ← "Daisy"` `players[4,2] ← "28"`	`# Each player has a name and a score` `players = [` `["Alice", 25],` `["Bob", 30],` `["Charlie", 22],` `["Daisy", 28]` `]`
Assignment	Assigning the name`Holly`to replace the name`Charlie`
`players[3,1] ← "Holly"`	`players[2][0] = "Holly" # Charlie is at index 2 (third row), name is at index 0`

Examples

Initialising a 2D array with 3 rows and 3 columns, with the specified values

Pseudocode

Python

Iterating through a 2-dimensions array

When iterating through a 2D array, a nested FOR...NEXT loop can be used
Nested iteration to access items in the 2D array

Pseudocode

Python

Exam Hint In the exam, the question will always give an example to demonstrate which order the array is being read from.

Some questions can be X,Y and others can be Y, X. Always refer to the example before giving your answer!

Worked Example A parent records the length of time being spent watching TV by 4 children

Data for one week (Monday to Friday) is stored in a 2D array with the identifier minsWatched.

The following table shows the array

Quinn Lyla Harry Elias
0 1 2 3
Monday 0 34 67 89 78
Tuesday 1 56 43 45 56
Wednesday 2 122 23 34 45
Thursday 3 13 109 23 90
Friday 4 47 100 167 23

Elias watched 78 minutes of TV on Monday:

Identify the row for Monday: Row 0.

Identify the column for Elias: Column 3.

Find the value at minsWatched[0][3]: The value is 78

Write a line of code to output the number of minutes that Lyla watched TV on Tuesday [1]

Write a line of code to output the number of minutes that Harry watched TV on Friday [1]

Write a line of code to output the number of minutes that Quinn watched TV on Wednesday [1]

Answers

print(minsWatched[1][1] OR print(minsWatched[1,1]

print(minsWatched[4][2] OR print(minsWatched[4,2]

print(minsWatched[2][0] OR print(minsWatched[2,0]

	Quinn	Lyla	Harry	Elias
0	1	2	3
Monday	0	34	67	89	78
Tuesday	1	56	43	45	56
Wednesday	2	122	23	34	45
Thursday	3	13	109	23	90
Friday	4	47	100	167	23

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Concept

Pseudocode

Python

Create

DECLARE scores: ARRAY[1:5]OF INTEGER

scores = []

Creates a blank array with 5 elements (1-5)

Creates a blank array

scores ← [12, 10, 5, 2, 8]

scores = [12, 10, 5, 2, 8]

Creates an array called scores with values assigned

Assignment

colours[4] ← "Red"

colours[4] = "Red"

Assigns the colour "Red" to index 4 (4th element)

Assigns the colour "Red" to index 4 (5th element)

Pseudocode

Python

DECLARE MyArray : ARRAY[1:5] OF INTEGER

array = [1, 2, 3, 4, 5]

Pseudocode

Python

MyArray[1] ← 1

array[index]

Pseudocode

Python

MyArray[index] ← newValue

array[index] = newValue

Pseudocode

Python

There is no built-in length function in CIE pseudocode. The array length is known from the declaration or stored in a variable.

len(array)

Pseudocode

Python

Concept

Pseudocode

Python

Create

Declare a 2D array with name and number for 3 people

Creates a 3x2 blank array (3 people, each with name and number)

DECLARE NamesAndNumbers : ARRAY[1:3, 1:2] OF STRING

1:3 = 3 rows → one for each person

1:2 = 2 columns → one for name, one for number

OF STRING → both names and phone numbers are stored as strings

NamesANDNumbers = [[None, None], [None, None], [None, None]]

Declare a 2D array calledplayerswithname andscoreassigned for 4 people (Alice, Bob, Charlie & Daisy)

// Declare a 2D array with 4 rows and 2 columns (name and score)

DECLARE players : ARRAY[1:4, 1:2] OF STRING

// Assign values to each player

players[1,1] ← "Alice"

players[1,2] ← "25"

players[2,1] ← "Bob"

players[2,2] ← "30"

players[3,1] ← "Charlie"

players[3,2] ← "22"

players[4,1] ← "Daisy"

players[4,2] ← "28"

# Each player has a name and a score

players = [

["Alice", 25],

["Bob", 30],

["Charlie", 22],

["Daisy", 28]

]

Assignment

Assigning the nameHollyto replace the nameCharlie

players[3,1] ← "Holly"

players[2][0] = "Holly" # Charlie is at index 2 (third row), name is at index 0

Pseudocode

Python

Pseudocode

Python

	Quinn	Lyla	Harry	Elias
0	1	2	3
Monday	0	34	67	89	78
Tuesday	1	56	43	45	56
Wednesday	2	122	23	34	45
Thursday	3	13	109	23	90
Friday	4	47	100	167	23

Quinn

Lyla

Harry

Elias

Monday

Tuesday

Wednesday

122

Thursday

109

Friday

100

167