Embedded Files
YOUR FIRST PROGRAM
An Example Program
First, open up processing. You’ll see a blank project with some weird name like sketch1032890.
Click on File → Save As
Find your Computer Science folder on your flash drive
Give your project a name, like HelloWorld.
Copy the example code below into Processing and run the program.
Look carefully at the console output at the bottom of your window.
Code:
void setup()
{
frameRate(1); // slows the program to run 1 frame per second
println("Hello World"); // prints Hello World then starts a new line
}
void draw()
{
print("*"); // prints a * each frame on the same line
}
Output after 1 second
Hello World
*
Try changing the line of code frameRate(1) to take a different value
What happens with 5? 30?
What happens if you delete this line of code?
Output after 1 second, assuming frameRate is 5:
Hello World
*****
Output after 1 second, assuming frameRate is 30:
Hello World
******************************
Output after 1 second if you delete the frameRate() line. This program runs at 60 frames per second.
Hello World
************************************************************
COMMENTS
Using Comments
A comment is a section of coder that doesn't have any effect, but acts as a note for the reader.
You can write comments in your code in two ways:
Use // to make a single line into an inline comment.
Use /* */ to make a whole chunk of code into an extended comment.
Code:
void setup()
{
// This is an inline comment
/* This is an extended
comment */
}
Hotkeys!
In processing you can select a whole block of code and press CTRL-/ (control and forward slash). Doing so will turn that whole section into a comment. You can do so again to turn the same code back to normal.
This is super useful for temporarily disabling code when debugging.
SETUP AND DRAW
Setup and Draw
In Roboquest, every program started with the go() method. In a normal processing program, you have two “main” methods, called setup() and draw().
void setup()
This method is called once at the start of the program
It is useful for things you only want to have happen one time
void draw()
This method is normally called 60 times per second
You can change this by using the frameRate() command
Draw is the main “event loop” that keeps the program running
THE CONSOLE
The Console
The black window where Processing output text is called the console. This is commonly used for text-based programs, but also for debugging our code. Sometimes it helps to print out the value of a variable, or information about what is going on.
Printing
There are two ways to print information:
Using the print command will output the data
Using the println command will output the data and start a new line
The console in Processing isn't quite as fun as the one you might have at home...
RESOURCES
Chapter 2 - Using Processing
Chapter 3.1, 3.2 - Setup and Draw
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