Introduction

Discuss some of the key vocabulary for this programming unit of work, which they should have heard before.

What is programming? - Giving instructions to machines to make them do something

What is an algorithm? - A set of instructions to solve a problem or make something happen.

computer program or code - When an algorithm is written in a language that a computer can understand.

 

Machines all around us are controlled by code. What are these machines? How do they work?

 

 

Talk about examples such as traffic lights, automatic doors which repeat the same commands.

Why is it important that they keep repeating?  How do you think computers can help control systems?

 

Computers can be told what to do (programmed) using coding languages and need to be given precise commands that are part of this language. 

This can look like many different things:

 

The buttons on a Bee-Bot:

 

 

Blocks in Scratch Jr:

 

Written coding languages like Python:

What is Logo?

Logo is the name of a programming language too. It was first created in 1967. We are going to learn how to program an on-screen sprite called a turtle, using Logo.

Many versions of Logo area available, including in Purple Mash and free websites like Turtle Academy.

 

Log into Purple Mash. Select Tools > Logo > Logo.

 

 

Getting started with Logo

Children may have had a brief introduction to Logo in Year 1, if they have completed our Year 1 unit of work Programming Direction. That unit has one lesson that introduces some basics in preparation for this unit.

Logo is a simple coding language that uses word and number commands instead of arrows etc.

Take a look at the main screen with the class. Ask them - have you used this before? What can you remember? How can we write code to give instructions in Logo?

 

 

Turning on the grid feature is really useful at this point, and is something we'd recommend the children use at all times, as the squares correspond to the number of steps you type.

 

 

Choose your turtle

The term screen turtle refers to the sprite or cursor that you program to move around the screen. In many Logo programs, this is an actual turtle sprite, as it was traditionally. However, the Purple Mash version of Logo gives you a choice of many different sprites for your turtle, including some turtles!

Show the children how you can pick your own by clicking the green arrow icon at the top of the screen.

 

 

You should be taken to the default category of 'Turtles', which are all birds-eye-view type images, and are ideal. But you can add any Purple Mash clipart images from the drop-down box.

 

 

Writing your first code

Show how you can click on the commands in the list of commands on the right of the screen to add it to the command line. Or you can just type them in, but either way, you need to press Enter to run each command or click the play button at the top of the screen. Each command makes the arrow do things. Another name for the arrow is a screen turtle.

Add ‘fd’ and press Enter, why doesn’t anything happen?  

 

 

Establish we need a number as well. Add another ‘fd’ and then a number (make sure there is a space between the command and the number).

 

 

How could we turn the screen turtle?  Lt and Rt will do this, but again we need to add a turn number. Establish that this is the number of degrees the arrow will turn, although it is not necessary to get deep into this, they just need to understand that it is a unit of measurement for turning and angles. Stick to two key numbers as options for them when turning - 90 and 45 degrees, and 90 degrees in particular as being a quarter turn.

 

Have a go!

Give the children some time to experiment with Logo, ask them to try out Fd and Bk with different distances and Lt and Rt but sticking to using 90 for all turns. They can also investigate what the command Home does (they’ll have to type ‘home’). This sends the screen turtle (arrow) back to where it started.

Once they have had some time to experiment, show them the reset button (rotating arrows) at the top of the screen which clears all drawn lines and returns the arrow to its starting position. 

 

 

Program a square

Ask - How could we program our turtle to draw a square? What would be the first command?  Take their suggestions and demonstrate, each command step-by-step and emphasising the need to use 90 degrees for the corners.

 

The commands could be:

fd 5 rt 90 fd 5 rt 90 fd 5 rt 90 fd 5 rt 90

 

 

Could we edit this code and still draw a square? 

 

Yes! The forwards distance could be larger or smaller. 

fd 9 rt 90   fd 9 rt 90   fd 9 rt 90   fd 9 rt 90

 

We could swap rt (right turn) for lt (left turn). But the turning angle must stay as 90 degrees. 

 

fd 5 lt 90   fd 5 lt 90   fd 5 lt 90   fd 5 lt 90

 

We could go backwards instead too.

bk 5 lt 90   bk 5 lt 90   bk 5 lt 90   bk 5 lt 90

 

Give the class some time to experiment with editing the code for a square in different ways

 

Rectangles

Ask them to clear their screen and have a go at drawing a simple shape like a rectangle with their screen turtle. Ask them to have a go drawing rectangles of different sizes and different orientations (tall and thin, wide and short). 

 

 

Plenary

Recap the commands they now know in Logo. What was difficult? Did they get better at estimating the distance of movements? How does the background grid help with this? What happens if you make a typing or spelling mistake when you give a command? Why?  Computers only follow exact instructions, they don’t usually interpret information (unless programmed to do so).  What is a programming language?