1. Computational Thinking (How to think like a computer scientist)
Lesson 3
Abstraction

2. Objectives To know the term ‘Abstraction’ means
Identify a use for abstraction in an algorithm

3. Recap - The four cornerstones of Computer Science

4. What is Abstraction?
Abstraction is one of the four priciples of Computer Science. 
Abstraction means to hide unnecessary detail
To draw a cat, we do need to know that it has a tail, fur and eyes. These characteristics are relevant.
We don't need to know what sound a cat makes or that it likes fish. These characteristics are irrelevant and can be filtered out.
We don't need to know what size and colour these are. These specifics can be filtered out

5. Video

6. Describing Algorithms
There are two ways of describing an algorithm:
Flowcharts – A graphical representation of the steps involved
Pseudocode – English like instructions detailing every step

7. Abstraction in Use
In the last lesson you decomposed the problem of drawing the house into a series of smaller problems
House
Draw
Chimney
Door
Windows
Outline

8. Drawing a Window
The abstraction for a window in this house is that it is square and has glazing bars which divide the window into 4 panes
The abstraction is not concerned about where the window is placed in the building

9. Activity 2 – Drawing the Windows
What other abstractions can you identify?

10. Houses