Standard Algorithms (SQA National 5 Computing Science): Revision Note

DECLARE age : INTEGER

REPEAT
    RECEIVE age FROM (INTEGER) KEYBOARD
    IF age < 0 OR age > 120 THEN
        SEND "Please enter a valid age between 0 and 120" TO DISPLAY
    END IF
UNTIL age >= 0 AND age <= 120

age = int(input("Enter your age: "))

while age < 0 or age > 120:
    print("Please enter a valid age between 0 and 120")
    age = int(input("Enter your age: "))

print("Thank you! Your age has been recorded as", age)

• This example uses a post-conditional loop (REPEAT…UNTIL) so that the program always asks for input at least once

• You could also use a pre-conditional loop (WHILE) if the input is read before the loop starts, both are valid as long as the logic is correct

• The while loop is conditional, it continues while the input is invalid

• The error message and new input are both inside the loop

• The loop stops only when the input is within the valid range (0–120)

DECLARE total : INTEGER ← 0

FOR counter ← 1 TO 10 DO
    RECEIVE number FROM (INTEGER) KEYBOARD
    SET total TO total + number
END FOR

SEND "The total is " & total TO DISPLAY

total = 0

for counter in range(1, 11):
    number = int(input("Enter a number: "))
    total = total + number

print("The total is", total)

• This program starts a total at 0 and then repeats 10 times

• Each time, it asks the user to enter a number and adds that number to the total

• After the loop ends, the total of all entered numbers is displayed

• In Python, it uses a for loop to run 10 times, adds up all the numbers the user enters, and then outputs the total at the end

DECLARE count : INTEGER ← 0

FOR counter ← 1 TO 10 DO
    RECEIVE number FROM (INTEGER) KEYBOARD
    IF number > 5 THEN
        SET count TO count + 1
    END IF
END FOR

SEND "The count is " & count TO DISPLAY

count = 0

for counter in range(1, 11):
    number = int(input("Enter a number: "))
    if number > 5:
        count = count + 1

print("The count is", count)

• This program keeps track of how many entered numbers are greater than 5

• It repeats 10 times, increasing the count by 1 each time the condition is true

• The final count is displayed after the loop ends

• In Python, it checks if each entered number is greater than 5, adds 1 to the counter when it is, and prints how many numbers met the condition

DECLARE scores : ARRAY[1:5] OF INTEGER
SET scores[1] ← 12
SET scores[2] ← 10
SET scores[3] ← 5
SET scores[4] ← 2
SET scores[5] ← 8

FOR index ← 1 TO 5 DO
    SEND scores[index] TO DISPLAY
END FOR

scores = [12, 10, 5, 2, 8]

for score in scores:
    print(score)

• This algorithm uses a fixed loop to move through the array from the first element (scores[1]) to the last (scores[5])

• Each element is accessed and displayed in order

• This Python program loops through the list scores, printing each value in turn

• The for score in scores statement automatically starts at the first element and ends at the last