Created by NW 2012 – please note all copyright on images used is property of copyright holder....

Created by NW 2012 – please note all copyright on images used is property of copyright holder. Note: some of the more complicated descriptions are taken from http://www.greenfoot.org/doc/ so credit to them too!

Greenfoot

Computer programmingLesson 1

Objectives

• Understand what programming is and its purpose.

• Develop awareness of basic programming skills and concepts.

• Create a simple program in Greenfoot.


What is a program?

• A program is a step-by-step set of instructions that tells a computer how to do something.

• A more geeky term is “algorithm” which is a step-by-step description of how to accomplish some task.


7 key points1. One of the first differences you have to understand between giving a set of

instructions for a person and one for the computer, is that the computer is an empty box that does nothing w/o programs or instructions.

2. A computer has little capacity to interpret things – it has to be told directly.3. The instructions you give to them have to be very precise.4. Computers do exactly what you tell them to do, nothing more, nothing less

(its not the computers fault you keep dying / losing / crashing, its you!).5. When you tell a computer to do something you also have to break it down

into steps that it can understand .6. The only steps a computer really understands are steps that are very small

and exact. 7. This means that in order to write programs we don’t use English – in this

instance we use a language called JAVA.


Why bother to learn to program?

• Nearly every activity you do in your daily life involves a computer, whether you realize it or not. When you think about computers in your life, you might only think of your desktop or laptop. However, your phone, iPod, and every other electronic gadget you might own these days is really a digital computer.

Quick challenge: List on paper how many computers you come across or use in a normal day.


Why bother to learn to program?

• Learning how to program is a great way for anyone to improve your problem solving capabilities (A bit like when your stuck in a game or trying to plan out the fastest route to somewhere).

• Most programs solve a type of problem for us. The first step in any programming task is figuring out how to solve the problem yourself in sufficient detail that you can give the instructions to a computer.Created by NW 2012 – please note all copyright on images used is property of copyright holder. Note: some of the more complicated descriptions are

taken from http://www.greenfoot.org/doc/ so credit to them too!

Greenfoot Chapter One Scenario• After copying the Greenfoot Book Scenarios to your network

folder, we will open chapter01/leaves-and-wombats ->double click on the icon for Greenfoot to execute the project.

• We need to right-click on the Wombat Class to add an object to the world. Your instructor will show you how to add the Wombat to the World.

1. When the program opens click on the COMPILE button.


Greenfoot Chapter One Scenario

• \

• We will go through Chapter One and discuss terms and concepts.

We will add a Wombat to our world. We click

RUN to make the Wombat move!

The Greenfoot interface

The World The Classes

Execution controls


Lets make a simple world1.Open Greenfoot and choose “create a new scenario”.

2. Name your game and save into your workspace

3. Right click on “world” and choose “new subclass”

4. Choose the background “sand.jpg. Then give it a suitable

name.

4. Choose the background “sand.jpg. Then give it a suitable

name. 5. Click on “compile to see your new

world.


Now lets add an object.1.Right click on Actor and choose New subclass.

2. Under animals choose “ant3” and name it “Ant” (at the top!).

3.Click on the Any object. Now HOLD SHIFT and click in your world

to place the ant.


Lets move our object.• You have noticed if we press RUN nothing happens –

that’s because we haven't told our ant to do anything (stupid ant is a computer and can’t think for itself)

RIGHT CLICK on the Ant object and choose the “open editor”

option. This is where all the fun begins! This is what is known as

the code.

Lets move onto making our Ant (object move) move.


Adding code• Add the following code into your Ant.


• Click on compile and place your ant into the world again. Now look what happens when you click run.

• You can change the speed of the ant by changing the number 4 in the code to a different number. Higher makes it faster, lower makes the ant slower -- see if you can guess what happens with a negative number. Then try it!


Some points to note when coding

• You have noticed you must precisely match what is written in the example.

• Common mistakes include:– capitalising the m– Capitalisation matters in Java! – Missing the semi-colon;;;;;;– using the wrong brackets (more in a second!)– or accidentally deleting the curly brackets. If you get

an error look for one of these errors that you might have made when copying the code.


Some points on brackets. • A quick note about brackets. There are three main

bracket types used in Java; let's see some blown-up images of them:

• Round brackets, known in the USA as parentheses, but in the UK simply as brackets. In Java, they are used in mathematical expressions, and to surround the lists for method calls (we'll get to those shortly).

• Square brackets, known in the USA simply as brackets (see where confusion can arise?). In Java, they are used for arrays.

• Curly brackets, also known as braces or squiggly brackets. In Java, these are used to surround blocks of code, such as methods or the contents of classes.


()[]{}

Changing the code

• Now see what happens if you change the code to the following:

Ok – finally lets try this…

Objectives

• Understand what programming is and its purpose.

• Develop awareness of basic programming skills and concepts.

• Create a simple programme in Greenfoot.


Created by NW 2012 – please note all copyright on images used is property of copyright holder....

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