Introduction

Recap the word ‘algorithm’, what does it mean? What kinds of algorithms have we looked at so far? Explain that we will be coming up with a different kind of algorithm today. We will have to do a lot of testing to see if they work and if they don’t we will debug them and improve our algorithm. Ensure students understand these terms.

Demonstrate on the board writing an algorithm for the morning routine for entering the classroom. Ask them to help with some of the instructions, what might the first instruction be?

Highlight examples of good precise instructions and demonstrate where sometimes instructions can be ambiguous and tricky to follow if they’re not precise - would a new child  to our class understand our instructions? Does it matter which order we do the instructions? Why?

 

The Human Crane carpet work

In this activity your hand is a crane that can be controlled with a series of 8 simple instructions:

 

 

 

Begin this as a whole class activity. You will need three buckets or similar containers, or just three sheets of paper to represent containers. You will also need three large 'blocks' that are each a different colour. These could be large building blocks, beanbags, balls etc.

The children must create algorithms to work the crane (their hand) to move blocks from one position to the next. They create the algorithms with the provided cards, and arrange them in rows on the desk to show the order of their algorithm.

The main rules are:

• The crane always starts above cup number 1 with its pincers open.
• All blocks start in cup 1.
• You cannot drop blocks from a height
• Don't move the crane unless instructed to

 

 

Explain to the children how the Human Crane works and the possible instructions you can give it. By showing the large teacher cards.

Look at the examples in the Teacher Presentation together, ask the class to help decide on a sequence of instructions (algorithm) to tell the crane what to do, where to move, when to open and close its pincers.

 

For example:

 

To move the red block to the middle cup the crane would need to perform the following actions:

1. Down
2. Grab (the red block)
3. Up
4. Right 1
5. Down
6. Open

As they choose an instruction get children to come out and hold the appropriate Teacher card (printed off A4), to create the algorithm.

Test what they come up with and decide if it needs debugging, this might involve working out where the mistake is and how we can fix it.  Does the order matter? What happens if we move an instruction? Can we use the same algorithm backwards?

 

The Human Crane main task

The students will then work in pairs on a smaller version of the same problem. Ask them to work with a partner to have a go at the challenges on worksheet 1 (to be printed back to back). You can give them actual paper/plastic cups, or use the Human Crane 'Cups' sheet to represent the cups. Each pair will also need three different coloured blocks (Lego, maths cubes etc). They should use the cups and blocks and take it in turn to be the crane; performing each sequence to work out the correct order for the instructions and test it.

Provide each pair with a set of cards so they can lay out the steps in the algorithm as they work it out. Each sheet of cards contains three of each instruction. The children may need more than this for some of the challenges so make some extra copies too.

When the have tested each challenge with their hand, and they have laid out the cards in the correct sequence, they can write the algorithm onto their worksheet in the arrow button boxes. They only need to use the arrow symbols shown to do this.

This more advanced version of the worksheet is also available which introduces a third block.

As they are working discuss with them:

If you could make up one new instruction that the human crane could understand, what would it be? (You can give them the option to make and add their own into the pack - e.g. a repeat card would be useful for some actions)

 

Plenary

At the end recap their understanding of ‘algorithm’ , ‘test’ and ‘debug’. Also discuss what was easy? What was difficult? Why? What new instructions could we teach the human crane to make it easier?