ACARA Digital Technologies Years 5–6 — Algorithms with Branching and Repetition Hangman

The 40 key terms

1algorithm

A set of clear steps, in order, that solves a problem or completes a task, like a recipe or morning routine. Each step must be precise so a person or computer can follow it.

2sequence

Steps that run one after another in a set order. Changing the order, leaving a step out or adding an extra step can change the result.

31. Get a bowl

A written algorithm step. Each line has one number and one action, and starts with a command word like Get, Add or Show. Steps go 1, 2, 3 in order.

4follow an algorithm

To carry out each step exactly as written, in order, without skipping steps or guessing. You can track values on paper, check the final result, or act it out with a partner.

5SET score TO 0

A variable is a named place that stores a value. SET gives it a value, like 0, and later steps can change it, such as ADD 1 to score, so it works as a counter.

6ASK and SHOW

ASK is an input step: it asks the user for a value and stores it in a variable. SHOW is an output step: it displays a result, like a message, on the screen.

7condition

A question about the situation that can only be answered true or false (yes or no), like 'Is it raining?' or 'Is the score above 10?'. It helps an algorithm decide what to do.

8IF condition THEN action END IF

Runs the indented action only when the condition is true. If the condition is false, the action is skipped. Write IF and THEN in capitals, indent the action, and finish with END IF.

9IF condition THEN action1 ELSE action2

Chooses between two paths. If the condition is true, action1 runs. If it is false, the ELSE path runs action2 instead. Exactly one of the two paths runs.

10ELSE IF

Checks another condition when the first one is false, so an algorithm can pick from more than two paths. Conditions are checked in order and only one path runs.

11nested IF

A second IF written inside the THEN or ELSE path of the first IF. It is only checked when that path is taken. Indent it and give each IF its own END IF.

12AND / OR

AND is true only when both conditions are true. OR is true when at least one is true. Saturday AND sunny needs both; Saturday OR sunny needs just one.

13iteration

Repeating a set of steps instead of writing them out again and again. The repeated steps are called the loop body. Loops save effort.

14repeating pattern

Same steps that appear again and again. Replace them with one loop to make the algorithm shorter, with the same result.

15REPEAT n TIMES

Runs the indented steps under it exactly n times, then moves on to the next step. Use END REPEAT to show where the loop stops. Example: REPEAT 5 TIMES.

16REPEAT ... UNTIL

A loop that keeps repeating its steps until a condition becomes true. Use it when you don't know how many times. Make sure the condition can happen, or the loop never stops.

17infinite loop

A loop that never stops because its stopping condition can never become true. Something inside the loop, like a counter, must change to work towards the condition.

18IF inside REPEAT

An IF placed inside a REPEAT is checked again on every repetition, so each pass through the loop can take a different path.

19SET count TO 0

Makes a counter. Set count to 0 before the loop, ADD 1 TO count inside the loop each time it repeats, then SHOW count after the loop.

20IF card = red THEN count ← count + 1

Inside a loop, the IF checks each item. Only when the item meets the condition does the counter go up by 1. If the condition is false, the counter stays the same.

21REPEAT UNTIL count = 5

A loop that keeps repeating its steps until the counter reaches the chosen number, 5. The counter must change inside the loop, or the loop never stops.

22sequence, branch, loop

Most algorithms mix steps in order (sequence), decisions (branch) and repeats (loop). When you read an algorithm, you can label each part and explain it in your own words.

23sequence, branching, iteration

The three building blocks of algorithms: steps in order, decisions (IF) and repeats (loops). Traffic lights, self-serve checkouts, automatic doors and alarm apps all use them.

24tracking table

A table with a column for each variable and a row for each step or repeat. It shows how the values change, and the first row holds the starting values.

25trace

To trace an algorithm, pick starting values, follow each step in order, write down how the values change, and say what it shows at the end.

26purpose

What the whole algorithm achieves. Follow the steps, check what it SHOWS and read the variable names for clues, then say it in one sentence.

27flowchart

A diagram that uses an oval for start and end, a rectangle for a step and a diamond for a yes or no question, all joined by arrows that show the order.

28decision diamond

A diamond shape in a flowchart that asks a yes or no question. One arrow is labelled Yes and one is labelled No, and each arrow leads to different steps.

29loop arrow

An arrow that goes back to an earlier shape so steps repeat. The loop stops when the decision's exit arrow is followed, such as when the answer is Yes.

30count ← count + 1

A flowchart counter: set count to 0 in a step box, add 1 inside the loop, then ask count = 5? in a diamond. Yes leaves the loop, No goes round again.

31trace a flowchart

Start at the oval, follow each arrow with your finger, answer every diamond using the current values, write down counter changes, and stop at the end oval to find the result.

32step = shape

Each numbered step becomes one flowchart shape. An IF becomes a diamond, and a REPEAT becomes an arrow going back to an earlier shape. Both versions should do the same thing.

33flowchart to steps

Changing a flowchart into written steps: a diamond becomes IF or a loop condition, a back arrow becomes REPEAT, then check both versions do the same thing.

34bug

A mistake in an algorithm. Follow the steps until the result goes wrong, then fix that step. It might be in the wrong order, missing, or unclear.

35test case

A chosen starting value you try in an algorithm, with the result you expect. Use one for every path and for a loop that runs zero times, then compare expected and actual results.

36IF or REPEAT

Use IF when a step happens only sometimes. Use REPEAT when the same steps happen many times. Use both together when a loop needs a choice inside.

37REPEAT UNTIL guess = secret

The guessing game loop: keep asking for a guess until it matches the secret number. Inside, decide too high, too low or correct, and add 1 to the count each time.

38quiz algorithm

An algorithm that repeats questions, adds 1 to a score variable for each right answer, and picks harder or easier questions depending on that score.

39design an algorithm

Start with the user's problem, list the steps the solution must do, then add any decisions and repeats. Think about what the user puts in and needs out, and test the steps with them.

40REPEAT + IF + count

A finished algorithm joins steps, a decision (IF), a loop (REPEAT) and a counter to solve a school, game or recipe problem. You check it by following it step by step.