Table of Contents

Logo

Logo is the best and simplest way to start real programming.

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Note for Teachers - Navigation is roughly organised by technique (repeat/subs/abstraction) rather than outcome (SQU, TRI, PENT, CIRC HOUSE, STREET, FOREST) but this rule has been broken.

Getting Started

Open the link below (right click > open in a new browser tab so you can switch back and forth). This site is an Online Logo Interpreter

Remember to keep this window open. You can always open it from this page if you accidently close it.

type the following in the box at the bottom

forward 100

Click Run Then try

right 90

Don't forget to click run

Hint

You can use the short commands fd 100 and rt 90

Task: draw a square

Then try a hexagon and a triangle

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Additional resources

Repeat

It gets boring typing all these commands. Using repeat is quicker. Try this command

repeat 4 [fd 100 rt 90]

Hint:

These are square brackets not curly ones!

Task: draw a pentagon

Then an octagon, decagon (What?), a 10 sided shape, then finish with a circle

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Sub Routines

Which is easier to understand and type?

repeat 4 [fd 100 rt 90]

or

squ

We are going to teach the computer how to SQU. Using the following code

to SQU
  repeat 4 [fd 100 rt 90]
end
  1. We need a bit more space so open the command window using the black arrow HELP!!
  2. Enter your code (from above)
  3. Click Run
  4. Click on Library (top right) to check that your code has been saved.
  5. Then to use the SQU command simply type SQU underneath
  6. The command clearscreen might be useful

Task:

Theory

When programming it's good name different bits of code. These different bits of code are called sub routines (we could also say: procedure, a function, a method or just a routine). Looking at it the other way around we could say that we are going to give a name to the repeat 4 [fd 100 rt 90] code that we have been using, to make it easier to remember and use.

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  1. I know HOW to use a subroutine
  2. I know WHY I am creating a subroutine

Abstraction

Now we have named some sub routines we can combine them into new things. It allows us to abstract (hide) the detail. Programmers also call this black boxing or deconstruction. This is one of the most important skill that programmers have: computational thinking.

Task 1: Create a House using SQU and TRI

HINT (don't use it unless you Reeelly need it!)

Task 2: (Harder) Create a street

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See Also

Wikipedia

ARC Challenges

Can you work out how to do the following?

Use the code

To ARC
  repeat 90 [fd 1 rt 1]
END

1. Flower

Start with the head first

2. Bird

Can you create a single bird like the ones used in this Flock picture (We will do the whole flock later)

Variables

We can use variables to vary the size of the square

Task: Use your own variables to change the size of shapes (eg. HEX, TRI, SQU)

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Extra Challange: Use variables in Subroutines like HOUSE that uses TRI and SQU (this is more complicated that you might think)

Random Variables

Randomness occurs in nature. Use a random variable is a powerful way for you to easily create a natural effect.

random 16 will produce a random variable between 0 and 16

for example random colour using the set pen colour command

setpc 16 where the number is one of 16 predefined colours

Random Challanges

Checkpoint

  1. I have used a random variable creatively to obtain a natural effect

Creativity: Logo Art

The best thing about Logo is having fun and doing something that interests you. This way you are sure to be creative.

What do you want to do today?

This image is created in Logo. You can buy a print of it to put on your wall. You can buy a book of images like this which includes the code used to generate it.

Task: Produce your own piece of art

See if you can get it printed in colour

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Power of: 15 Word Logo Challanges

Lots of inspiration here to use tiny amounts of code (15 words max) to produce a big effect

click image to visit the site

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Recursion

Recursion is an extremely powerful programming technique. It is a loop that 'calls' itself.. a bit like a snake eating its tail. If you don't tell in when to stop it can crash your computer - so it can be dangerous

Recursion is used to create fractals ![](http://upload.wiki(/media.org/wikipedia/commons/8/82/Mandelbrot-similar-x2000.jpg)

It is useful for searching a file system. It goes down from the root into each and every branch (folder) of the system. It is also used by nature to create things like trees. You can see the tree and fern in the examples on Calormen (Josh Bell's) Logo Interpreter

![](http://upload.wiki(/media.org/wikipedia/commons/f/fd/Von_Koch_curve.gif)

Here is TEF's "Papert Logo Online" with code for the Koch Snowflake

Quote

"The power of recursion evidently lies in the possibility of defining an infinite set of 
objects by a finite statement. In the same manner, an infinite number of computations 
can be described by a finite recursive program, even if this program contains no explicit 
repetitions. 

Wirth, Niklaus (1976). Algorithms + Data Structures
http://en.wikipedia.org/wiki/Recursion_(computer_science)#cite_note-3)

See Also

Challange/Task

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This is a complex task which will be beyond the reach of most students.. but have a go! Most important is to UNDERSTAND

3D Logo: Elica

Elica is a powerful and modern logo that can produce 3D and moving images.

See Also:

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I have watched at least 2 videos

Teachers Notes

link to this lesson

Also recursive

???