Arrays (SQA National 5 Computing Science): Revision Note

1-Dimensional Arrays

What is an array?

• An array is an ordered collection of data items stored under one variable name

• Each item in the array is called an element, and each element can be accessed using an index

• An array can only store one data type (for example, all integers or all strings)

• A 1-dimensional (1D) array stores data in a single list

• Indexes start at 0 in most programming languages such as Python

• In SQA pseudocode, arrays may start at 0 or 1, always follow the range given in the question

Concept comparison

Example in pseudocode

• Creating a one-dimensional array called array that contains 5 integers

DECLARE array : ARRAY[0:4] OF INTEGER

SET array[0] TO 1
SET array[1] TO 2
SET array[2] TO 3
SET array[3] TO 4
SET array[4] TO 5

SEND array[0] TO DISPLAY      // Output: 1
SEND array[2] TO DISPLAY      // Output: 3

SET array[1] TO 10            // Modify element at index 1
SEND array TO DISPLAY          // Displays [1, 10, 3, 4, 5]

FOR counter FROM 0 TO 4 DO
    SEND array[counter] TO DISPLAY
END FOR

SET length TO 5
SEND length TO DISPLAY         // Output: 5

Example in 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