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Computer Science GCES AQA

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  1. Representing Algorithms Aqa
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  2. Efficiency Of Algorithms Aqa
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  3. Searching Algorithms Aqa
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  4. Sorting Algorithms Aqa
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  5. Data Types Aqa
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  6. Programming Concepts Aqa
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  7. Arithmetic Relational And Boolean Operations Aqa
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  8. Data Structures Aqa
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  9. String Manipulation Aqa
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  10. Random Number Generation Aqa
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  11. Structured Programming Aqa
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  12. Robust And Secure Programming Aqa
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  13. Number Bases Aqa
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  14. Converting Between Number Bases Aqa
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  15. Units Of Information Aqa
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  16. Hardware And Software Aqa
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  17. Boolean Logic Aqa
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  18. Programming Languages And Translators Aqa
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  19. Cpu Architecture Performance And Embedded Systems Aqa
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  20. Memory Aqa
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  21. Secondary Storage Aqa
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  22. Fundamentals Of Computer Networks Aqa
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  23. Fundamentals Of Cyber Security Aqa
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  24. Methods Of Preventing Cyber Security Threats Aqa
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  25. Relational Databases Aqa
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  26. Ethical Legal And Environmental Impacts Aqa
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Exam code:8525

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 Tips and Tricks

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]

Responses

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