1 Introductory Lesson 3

What you will need

‘Getting to school’ starter

Projector / Whiteboard / Display screen

Learning Expectations (how learning / progress will be demonstrated)

All Explain the purpose of a flow chart.

Most Produce a flow chart for getting ready for school.

Some Produce a flow chart for getting ready for school which includes sub routines & conditions.

Learning Objectives

Understand algorithms (written in pseudocode or flow diagram), explain what they do, and correct or complete them.

Produce algorithms in pseudocode or flow diagrams to solve problems.

Break down (decompose) a problem into smaller steps.

Overview

In this lesson, students will produce an algorithm for getting ready for school and present this in the form of a flowchart.

Students will also learn how to use decomposition to break a problem down into smaller steps.

Curriculum Links (Computing PoS)

Understands what an algorithm is and is able to express simple linear (non-branching) algorithms symbolically. (AL)

Designs simple algorithms using loops, and selection i.e. if statements. (AL)

Designs solutions by decomposing a problem and creates a sub-solution for each of these parts. (DE) (AL) (AB)

Computational Thinking Concepts: AB = Abstraction; DE = Decomposition; AL = Algorithmic Thinking; EV = Evaluation;

GE = Generalisation.

Introductory Lesson 3 Algorithms

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2 Introductory Lesson 3

Teacher’s guide

Overview

In this activity students will decompose the act of getting ready for school and present this in the form of a flowchart. In

doing so the students will create an algorithm – a sequence of instructions to make something happen.

Starter

Hand out the starter activity ’getting ready for school algorithm‘ and ask students to place the blocks in the correct order.

Main

Ask a volunteer to go through the solution to the sorting exercise - ’getting ready for school algorithm’. After the volunteer

has provided their solution, ask the rest of the group if someone has a different solution and ask them to read it out to the

rest of the class. Note any differences between the two solutions (for example, one student may get dressed before having

breakfast whilst another may prefer eating breakfast in their pyjamas). Use these difference to explain that, as with

programming, there is no one right answer. Also ask students to suggest any daily routines that they think are missing from

the starter exercise, for example, doing their hair or checking their messages on their phone.

Explain to the students that they have just created an algorithm—put simply, a sequence of steps for completing a task.

Show students the diagram below. Challenge the students to give examples of how each symbol might be used – giving

prompts where necessary.

Explain that algorithms can be represented in many ways, the most commonly used being flowcharts and/or pseudocode.

Place students into small groups and ask them to pick one of the steps from the starter activity and create an algorithm (in

the form of a flowchart).

Tip: The going to school algorithm is great for demonstrating decomposition as you can have several sub-routines for

brushing your teeth, taking a shower, making breakfast etc., however, feel free to change the example as you see fit.

Alternatives to ‘getting ready for school’ may include: making a cup of tea, making a pizza, walking to school etc.

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3 Introductory Lesson 3

Teacher’s guide

Whilst the students are busy creating their flowcharts, wander around the classroom and pick out some examples. Read

out or re-enact the instructions in front of the students. At this point, it is important to be as pedantic as possible for

example: if an instruction reads ’pick up tooth brush’, ask the students ’What with?’ or ’Which end?’ or ‘Which

tooth brush?’. This will encourage the students to be more precise with their instructions.

After a short while, stop the class. Explain to them that they have just created a sub-routine. Show the example below.

Ask students why they think it’s important to have sub-routines in their algorithms—draw out answers such as ’breaks the

problem down into smaller steps’ or ’makes the problem easier to understand’ etc.

Challenge students to improve their algorithm to by including at least one sub-routine and one decision.

Example:

Plenary Revisit the term algorithm. Remind students that an algorithm is simply a sequence of instructions to make something

happen. Ask students to review their algorithms and explain what would happen if the instructions were in the wrong

order or if vital instructions were missing. Revisit the term decomposition and explain that we use this to simplify problem

and make solving it much easier.

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Symbol for a sub-routine

Example:

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Starter—Getting ready for school

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Place the steps below in the correct order.

Write a separate algorithm for at least one of the steps above, for example:

Pack school bag: 1. Pick up bag, 2. Open bag, 3. Place books in bag etc.

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5 Introductory Lesson 3

Extension

Challenge students to simplify their algorithm or reduce the number of steps by including more sub-routines.

Differentiation

To support students, reduce the set of cards for each algorithm.

To stretch students, challenge them to produce a digital version of their flowchart using suitable software.

Homework

Challenge students to create an algorithm for an every day task such as making the tea, tying a shoelace, making a jam

sandwich etc.)

Links

The Big Bang Theory—The friendship algorithm (Introduces students to the concept of flowcharts): https://

www.youtube.com/watch?time_continue=1&v=k0xgjUhEG3U

System flowcharts—BBC Bitesize: http://www.bbc.co.uk/schools/gcsebitesize/ict/

measurecontrol/2systemflowchartrev1.shtml

Disclaimer: Use these sites at your own risk. Acer is not responsible for the content of external Internet sites. We

recommend that you check the suitability of any recommended websites links before giving them to students.

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