1. Variables

2. What will we learn today?
What Are Variables
Variables in Real-Life
Variables in Programs
Types of Variables
Creating a Timer Example

3. Variables
A Variable is a storage location (place in computer’s memory) which contains information
Variables are analogous to "Buckets" or "Envelopes" where information can be maintained and referenced
Each variable has a name (an identifier), a type and a value (piece of information)
E.g. (a=5, b=“hello”)
Variables allow us to keep track of changes as our program runs

4. Variables in Real Life
We use variables to track the balance of money in a bank account
We use variables to track the amount of gasoline in the tank of the car

5. Variables in Programs
We often need to keep track of changes in position, color, and other properties of objects in our programs
In a game, we may want to keep track of number of steps or times or numbers of goals..etc
For example, we want to know the number of times a player has put the basketball through the hoop or how much time is left on the clock

6. Types of Variables Numeric Boolean Character/String Object
They can store a whole number value, e.g. 7 or 1024
Boolean
They can represent one of two states, true or false
Character/String
They can represent a single character, e.g. 'A' or '$‘ or a group of characters, e.g. “Ali” or “20 minutes left”
Object
They can represent a whole object, e.g. cat or fort

7. A Timer for a Game Example
A timer is used in most of the games to keep track of how much time the player has left to play
We will construct a timer that counts down in seconds
Our task is to set the timer to an initial number of seconds (e.g. 10s) and then count down the seconds remaining in a game
The number of seconds remaining will be displayed and will be updated with each passing second
We will create a chicken that rotates around itself as the timer count down

8. A Timer for a Game Example
Add a new object: a 3D text
Type 0.0 which is the value that appears when the time’s over

9. A Timer for a Game Example
Rename the object to timer

10. A Timer for a Game Example
Add a new variable in the timer object
Select the timer object
Select the properties tab
Click on the ‘create new variable’ button
Name it ‘timeLeft’ and set it to type ‘number’

11. A Timer for a Game Example
Drag the ‘timeLeft’ to the ‘world.timer’ method
Create a new parameter and call it ‘amount of time’

12. A Timer for a Game Example
Set the values as shown
Create a new method and call it ‘countDown’

13. A Timer for a Game Example
Inside the method, add a while loop with expression ‘a<b’ and set ‘a’ and ‘b’ as follows
Drag the text inside the while loop

14. A Timer for a Game Example
Set the value of the text as follows, drag ‘what’ from the functions box
Drag time left from properties insert it into the what box

15. A Timer for a Game Example
Move the timer up and down
Make a function that returns the time left

16. A Timer for a Game Example
The ‘countDown’ method
Create a method ‘playGame’ and set it as follows

17. A Timer for a Game Example
The main method ‘world.myFirst’ method

18. A Timer for a Game Example
Here is our Chicken

19. Let’s Work with Alice Counting Fishes
A Scuba diver (people) wants to count the fishes (ocean) that eat from the Seaweed (ocean).
Make a method where each fish goes to the seaweed, eats, waits, and comes back.
As each fish does so, a counter on the top-right corner of the screen (3D-Text) increases by one. After all fish have eaten, the scuba diver says the final count of fishes. You will need to create a number variable ‘NumberOfFish’ for that.