Pseudocode (SQA National 5 Computing Science): Revision Note

Pseudocode

What is pseudocode?

• Pseudocode is a text-based way of describing the steps in an algorithm

• It uses short English statements to show what the program should do, without using the full syntax of a programming language

• Pseudocode is structured and logical, helping you plan your solution before coding it

Example

• A website wants a program that asks users to enter their age

• If they are 18 or over, they are allowed to enter the site

• If they are under 18, they are shown a suitable message

RECEIVE age FROM KEYBOARD
IF age >= 18 THEN
    SEND "Welcome to the site" TO DISPLAY
ELSE
    SEND "Sorry, this site is for users aged 18 and over" TO DISPLAY
END IF

• The program asks the user to enter their age

• The value entered is stored in a variable called age

• The IF statement checks whether the user is 18 or older

• If the condition is true, the message “Welcome to the site” is displayed

• If the condition is false, the message “Sorry, this site is for users aged 18 and over” is displayed

• The program then ends after showing the correct message

Example (refined version)

• The website now wants the program to ask for the user’s first name and use it to greet them

RECEIVE firstName FROM KEYBOARD
RECEIVE age FROM KEYBOARD
IF age >= 18 THEN
    SEND "Welcome to the site " & firstName TO DISPLAY
ELSE
    SEND "Sorry, this site is for users aged 18 and over" TO DISPLAY
END IF

• The program first asks for the user’s first name and stores it in firstName

• It then asks for the user’s age and stores it in age

• The IF condition checks whether the age entered is 18 or more

• If it is, the program joins (“concatenates”) the text “Welcome to the site” with the user’s name and displays it, for example:

  • Welcome to the site Sarah

• If the age is under 18, the program displays the same rejection message as before

• The program then ends