Arrays (AQA GCSE Computer Science)

Revision Note

Test yourself

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

  • Indexes start at 0, known as zero indexed

1d-array-example

Concept

Pseudocode

Python

Create

array scores[5]

scores = []

Creates a blank array with 5 elements (0-4)

Creates a blank array

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 (5th element)

Example in Python

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

  • Create the array with the following syntax:
    array = [1, 2, 3, 4, 5]

  • Access the individual elements of the array by using the following syntax:
    array[index]

  • Modify the individual elements by assigning new values to specific indexes using the following syntax:
    array[index] = newValue

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

Python

# Creating a one-dimensional array
array = [1, 2, 3, 4, 5]

# Accessing elements of the array
print(array[0])   # Output: 1
print(array[2])   # Output: 3

# Modifying elements of the array
array[1] = 10
print(array)      # Output: [1, 10, 3, 4, 5]

# Iterating over the array
for element in array:
    print(element)

# Output:
# 1
# 10
# 3
# 4
# 5

# Length of the array
length = len(array)
print(length)     # Output: 5

2-Dimensional Arrays

What is a 2-dimentional 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

array players[3,3]

players = [],[]

Creates a blank 2D array with 3 elements (0-2)

Creates a blank 2D array

players ← ["Rob","Paul","Hayley"],[10, 5, 8] 

players = ["Rob","Paul","Hayley"],[10, 5, 8] 

Creates a 2D array called players with values assigned

Assignment

players[0,1] ← "Holly"

players[0][1] = "Holly"

 Assigns the name "Holly" to index 0, 1 (1st row, 2nd column) - replaces "Paul"

Example in Python

Python

# Initialising a 2D array with 3 rows and 3 columns, with the specified values
array_2d = [[1, 2, 3],
            [4, 5, 6],
            [7, 8, 9]]

# Accessing elements in the 2D array
print(array_2d[0][0])  # Output: 1
print(array_2d[1][2])  # Output: 6

Examiner Tip

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

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

  • print(minsWatched[0,2] or print(minsWatched[0][2]

Last updated:

You've read 0 of your 10 free revision notes

Unlock more, it's free!

Join the 100,000+ Students that ❤️ Save My Exams

the (exam) results speak for themselves:

Did this page help you?

James Woodhouse

Author: James Woodhouse

Expertise: Computer Science

James graduated from the University of Sunderland with a degree in ICT and Computing education. He has over 14 years of experience both teaching and leading in Computer Science, specialising in teaching GCSE and A-level. James has held various leadership roles, including Head of Computer Science and coordinator positions for Key Stage 3 and Key Stage 4. James has a keen interest in networking security and technologies aimed at preventing security breaches.

Lucy Kirkham

Author: Lucy Kirkham

Expertise: Head of STEM

Lucy has been a passionate Maths teacher for over 12 years, teaching maths across the UK and abroad helping to engage, interest and develop confidence in the subject at all levels.Working as a Head of Department and then Director of Maths, Lucy has advised schools and academy trusts in both Scotland and the East Midlands, where her role was to support and coach teachers to improve Maths teaching for all.