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When Steps Are in the Wrong Order

Put on shoes before socks and something feels wrong. Open the plan-order lab, watch a plan fail, then drag steps until inputs come before outputs.

Class 3 to 5beginner15 min3 lessons1 interactive lab
By the end you will be able to
  • Spot when step order makes a plan impossible
  • Reorder steps so each one has what it needs
  • Test a fixed plan and compare it to the broken one

Finish first

Game Rules Are Algorithms
Topic contents

Lesson 1 of 3

When order breaks the job

Some mistakes are not wrong words but wrong order. Tie shoes before you put them on. Frost a cake before it bakes. The steps make sense alone but fail together.

Computers are strict about order. They do step one, then step two, with no common sense to fix your mistake. That is why order bugs are so common.

Open the plan-order lab beside this lesson. Run the broken plan and watch where it stops making sense.

Interactive lab

Plan order

Watch a morning plan run in the wrong order and fail, then reorder steps until getting dressed comes before leaving.

Plan order

Put steps in the right order before you start

Get ready for school

You wrote a plan before doing the job. Step through it like a robot would.

  1. 1.Leave for school
  2. 2.Pack your bag
  3. 3.Put on shoes
  4. 4.Put on socks
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Wrong plan

Leaving first sounds fast, but you are not dressed and your bag is empty. Order matters.

Continue

Lesson 2 of 3

Inputs before outputs

Think of each step as needing inputs. Baking needs batter. Batter needs mixing. Mixing needs ingredients on the counter. Work backwards from the goal to find the right order.

In the lab, drag steps until every step has what it needs ready. Homework apps that ask you to save only after you type are another example of order mattering.

Read the fixed plan aloud. If you hear because before the reason is ready, swap those lines.

Continue

Lesson 3 of 3

Test after you fix

A fixed plan should run start to finish without a stuck moment. In the lab, play the success animation and compare it to the failure you saw first.

On paper, trace with your finger. After each step ask: do I have what I need for the next line? The first no is where order was wrong.

Next you will plan a whole week. Many small ordered lists can live inside one bigger capstone plan.

Continue

Practice

Work these out yourself

No answer key here on purpose: these are the questions worth thinking through before you move on. Open one and work it out.

0/3 attempted

Assessment

Check your understanding

Answer each question, then read the explanation. That is where the learning is.

0/4
  1. Question 1: Putting on shoes before socks fails because what?
    Question 1 / 4

    Putting on shoes before socks fails because what?

    Select an option first
  2. Question 2: A good way to fix order is what?
    Question 2 / 4

    A good way to fix order is what?

    Select an option first
  3. Question 3: In the plan-order lab, the broken plan mainly shows what?
    Question 3 / 4

    In the plan-order lab, the broken plan mainly shows what?

    Select an option first
  4. Question 4: After reordering, you should what?
    Question 4 / 4

    After reordering, you should what?

    Select an option first
4 of 4 questions left.

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