Programming with Alice
Computing Institute for K-12 Teachers
Summer 2011 Workshop
Session 0
Workshop Expectations

This workshop is designed to introduce programming
concepts through the use of the intuitive programming
environment of Alice.

Each of the seven Alice sessions will focus on one or more
of these concepts.

Throughout the workshop, there will be a chance for you to
use your new skills to create teaching aids for your subject
while introducing programming concepts to your students.
Alice Overview

Created by Carnegie Mellon in 1999

100% GUI based programming environment

Object-oriented

Multi-threaded

Runs on Windows and Mac

Free!
Set up environment

Let us create our first
example program. This
program will consist of
adding an object to the
world and making it
move.

Open Alice by doubleclicking the icon on the
desktop

Click the templates tab

Select one of the preset
environments

Click open
Alice Interface

The Alice interface is divided into five major sections:

The section on the upper left is called the object tree. This
contains a list of all the objects that currently exist in the
world.

The lower left section is the object details area and shows
information about the currently selected object.

The upper center section is the world window. This
provides an interactive view of how the world will look
when ran.

The top right corner is known as the events area. Most
methods of interaction with the user occur here.

The remaining section is the editor area. This is where the
actual programming takes place.
Objects in Alice

Alice, like many other programming languages, is object
oriented. Objects provide a basis for program structure and
serve to organize and simplify the design. Programming
with objects is often intuitive because of the nature of
human interaction with the world.

Objects consist of three basic elements:
◦ Properties – also known as variables, these are the
characteristics of the object much like hair color and
height are for us. These will be discussed in greater
detail during session 4.
◦ Methods – allow objects to do things such as move, turn,
resize, etc. Methods will be discussed in greater detail
during session 5.
◦ Functions – allow objects to do calculations. In session 5,
we will create a function that calculates the rotation of a
vehicle wheel in relation to the distance it moves.
Default Objects in Alice

All Alice programs contain at least four objects. These are:
◦ World - think of this as the virtual universe. All other
objects exist in and are “owned” by it. Unlike other
objects, it is impossible to move the world object.
◦ Camera – this supplies the view used by the world
window and is determined by the placement and
orientation of the camera object.
◦ Light – as the name implies, this object provides a
source of light to the scene and can be moved or
otherwise manipulated to alter the brightness and/or
shadows in the world.
◦ Ground – the xz-plane that serves as a reference point
for the user to place other objects.
Add Object to World

To enter object
management mode, click
the green button in the
lower right corner of the
world window.

Find a vehicle object with
wheels (not the
ambulance) and drag it to
the ground in the window
above.

For advanced positioning
instructions, please refer
to the presentation notes.
Object Manipulation Tools

Allows you to select an object and move it on the
horizontal plane

Moves an object on the vertical plane

Rotates an object around the y-axis of the world window

Rotates an object around the x-axis of the world window

A combination of the previous two tools. It is very hard to
control and should probably be avoided

Increases or decreases the size of an object

Creates a clone of an object
Renaming Object

In the object tree,
find the newly added
object, right-click it,
click “rename,” and
enter a new name.

The new name should
be short, descriptive,
and meaningful.
First Program: Moving an Object

Let’s learn how to use the
block.

Orient the vehicle so it looks as though it will be driving to
the right. You probably will need to move the camera
and/or adjust the size of the vehicle.

Select your object and move it as far as you can to the left
of the screen.

It is time to close object management mode in order to
open the method editor. To do this, simply click the
button.

To make this object move, select it by left clicking the
vehicle, click the methods tab in the object details area and
drag a move block to the editor area.
First Program cont.

A drop-down menu will appear and you can choose the
direction the object will move; mouse-over “forward”. You
should see another drop-down menu where you can select
how far it will move, select ½ meter for now.

Now we are ready to test our first program. In the top lefthand corner you will find the
button. Anytime you
want to test your project, simply click this button.

If your object didn’t move a satisfying distance or it didn’t
move in the correct direction you can edit this by left
clicking the down arrow to the right of the attribute you
want to change.

A menu will drop down and you can choose a new value.
Multithreading

Now we have our vehicle moving to the right, it is time to
make the wheels turn or rotate while the vehicle is moving.
To make two or more things happen at once we use a
programming convention known as multithreading.

In order to affect only the wheels of your vehicle, click the
plus button to the left of it in the object tree. This will
make the sub-parts of the object visible which will allow
you to manipulate them individually. For now, just select
one of the wheels (preferably one that can be seen in your
world window)

To make the wheel turn, drag a
block and place
it in the editor area. Choose a direction for it to turn and
test your program.

If the wheel doesn’t turn properly, change the direction or
try the
.
Multithreading cont.

Even though we have the vehicle moving and the wheel
rotating, it still isn’t perfect because the vehicle moves,
then the wheel rotates. The reason? Alice, like most other
programming languages, processes statements starting
from the top and moving down one by one. In order to
have the vehicle move while the wheel rotates, we must
use a new block.

Place a
container into the method editor and place
the move and turn blocks inside it.

This brings up the subject of multithreading. Many
programming languages take advantage of this
functionality. It allows the programmer to make multiple
things happen at the same time. For example, the vehicle
will move at the same time the wheel is turning. Now let’s
test this and make sure everything works properly.
Project 0

Now that we know how to use a do together container to
implement multithreading, try to get the other wheels of
your vehicle spinning. They should all spin at the same
time. This may take some playing around, but it is
possible. You should also change the wheels rate of spin to
look as realistic as possible in relation to the ground. In
session 5 we will explain how to do this more efficiently.