Repeat until

Question 1

A free drinks machine provides 20 different drinks.
The machine has a small keypad with keys 0-9, Submit and Cancel. It has a
small LCD display, which can display messages to the user.
To get a drink the user selects it by typing in the relevant number (1-20). If
they type in the wrong number, they can cancel and enter a new number.
When they are happy with their choice they press the submit button. If the
selection is valid (1-20) and the drink available, the machine will dispense
the drink.
Write an algorithm in pseudocode which for the process outlined above

Answer 1

Choice = “”
REPEAT
INPUT Button
IF Button is between 0 and 9 THEN
Choice = Choice & Button
OUTPUT Choice
ELSE IF Button = CANCEL THEN
Choice = “”
END IF
UNTIL Button = OK
IF Choice is between 1 and 20 THEN
IF drink chosen available THEN
Dispense drink
OUTPUT “Collect your drink”
ELSE
OUTPUT “Drink not available”
END IF
ELSE
OUTPUT “Invalid selection”
END IF
Wait
OUTPUT “Ready”