Decomposition (Computational Thinking)

Decomposition

Computational Thinking - Lesson 2

S2 Computing Science - Remote Learning

Lesson objectives:

• understand what decomposition is

• identify examples of decomposition

• successfully answer questions about decomposition

Lesson structure:

This lesson explains decomposition, one of the four cornerstones of computational thinking.

It includes, text, images, links to video and multiple choice questions.

Use the information, and any images from the presentation or elsewhere, to build up your own 'textbook' of learning using Book Creator on your iPad. You should already have started this.

Read all the information carefully as there are a number of timed questions afterwards.

Introduction

Before computers can solve a problem, the problem and the ways in which it can be resolved must be understood.

Decomposition helps by breaking down complex problems into more manageable parts.

What is decomposition?

Decomposition is one of the four cornerstones of Computer Science.

It involves breaking down a complex problem or system into smaller parts that are more manageable and easier to understand.

The smaller parts can then be examined and solved, or designed individually, as they are simpler to work with.

Why is decomposition important?

If a problem is not decomposed, it is much harder to solve.

Dealing with many different stages all at once is much more difficult than breaking a problem down into a number of smaller problems and solving each one, one at a time.

Breaking the problem down into smaller parts means that each smaller problem can be examined in more detail.

Similarly, trying to understand how a complex system works is easier using decomposition.

For example, understanding how a bicycle works is more straightforward if the whole bike is separated into smaller parts and each part is examined to see how it works in more detail.

Decomposition in practice

We do many tasks on a daily basis without even thinking about – or decomposing – them.

The following two slides look at the examples of:

1) brushing our teeth

2) solving a crime

Example 1: Brushing our teeth

To decompose the problem of how to brush our teeth, we would need to consider:

_* which toothbrush to use

_* how long to brush for

_* how hard to press on our teeth

_* what toothpaste to use

Example 2: Solving a crime

A more complex task requires more detail – to decompose the task.

Imagine that a crime has been committed.

Solving a crime can be a very complex problem as there are many things to consider.

For example, a police officer would need to know the answer to a series of smaller problems:

_* what crime was committed

_* when the crime was committed

_* where the crime was committed

_* what evidence there is

_* if there were any witnesses

_* if there have recently been any similar crimes

The complex problem of the committed crime has now been broken down into simpler problems that can be examined individually, in detail.

Decomposing creating an app

Imagine that you want to create your first app.

This is a complex problem - there are lots of things to consider.

How would you decompose the task of creating an app?

Decomposition: a series of smaller problems

_* what kind of app you want to create

_* what your app will look like

_* who the target audience for your app is

_* what your graphics will look like

_* what audio you will include

_* what software you will use to build your app

_* how the user will navigate your app

_* how you will test your app

_* where you will sell your app

Watch a video explanation

Copy the link into the address bar of your web browser to view a video explanation of decomposition:

https://www.youtube.com/watch?v=8HFqzzZxV9k

Multiple Choice

What is decomposition?

• Breaking down a complex problem or system into smaller, more manageable parts

• Adding detail to make a problem more complex

• When you ignore the unnecessary detail in a problem

Multiple Choice

Why do we decompose a complex problem?

• To make it more difficult to solve

• To change the problem we have

• To make it easier to solve

Multiple Choice

Which of these is an example of decomposition?

• Watching a mechanic repair a bicycle

• Looking at different bicycles for similarities between them

• Finding out how a bicycle works by looking in detail at the different parts that make up the bicycle

Multiple Choice

Which of these is an example of decomposition?

• Breaking the problem of organising a cake sale into smaller parts, such as who will bake the cakes and when to hold the cake sale

• Taking the problem of baking a cake and thinking about how we can make it the best cake possible

• Looking at what different kinds of cake can be made

Multiple Choice

How often do we decompose problems?

• We never decompose them, computers do this for us

• On a daily basis, often without thinking about it

• Occasionally, but we don't really need to

Multiple Choice

Which of these would NOT be involved in decomposing a problem?

• Thinking about how the problem could be divided into smaller parts

• Working out who could help you solve a part of the problem

• Adding more parts to the problem so it becomes more complex

Multiple Choice

Which of these is an example of decomposition?

• Guessing who has solved a crime from looking at patterns that have happened before

• Solving the complex problem of a crime by breaking it down into when the crime was committed and were there any witnesses

• Looking at what different crimes could be committed

Poll

How well do you rate your understanding of decomposition?

How well can you give examples of decomposition?

• Excellent

• Very good

• Good

• Satisfactory

• Poor