SelectionRepresenting selection

There are two ways of representing algorithms:

• pseudocode
• a flow diagram (also known as a flowchart)

Representing selection in pseudocode

Writing in pseudocode is rather like writing in a programming language. Each step of the algorithm is written on a line of its own, in sequence.

Look at this simple six-step algorithm for comparing your dog’s age with your own:

• ask how old the dog is in human years
• multiply human years by seven to find out how old the dog is in dog years
• print the answer on the screen
• ask how old you are
• if the dog’s age in dog years is older than your age, say ‘Your dog is older than you!’
• otherwise, say ‘Your dog is not older than you.’

In pseudocode, the algorithm would look like this:

OUTPUT 'How old is your dog?'
INPUT user inputs their dog's age in human years
STORE the user's input in the human_years variable
dog_years = human_years * 7
OUTPUT 'In dog years, your dog is aged ' + dog_years
OUTPUT 'How old are you?'
INPUT user inputs their age
STORE the user's input in the user_age variable
IF dog_years > user_age THEN OUTPUT 'Your dog is older than you!'
ELSE OUTPUT 'Your dog is not older than you.'

NOTE: when using pseudocode, you do not need to use THEN with IF and ELSE - although you can if you want to.