Processing

Processing is a programming language designed for the visual arts community. It is open source and uses basic syntax for creating drawings, animations, and interactive programs. It also includes a basic IDE, which serves as the programming interface.

Each program created in Processing is called a "sketch" and can be saved in a sketchbook. They are uncompiled source code files and are saved in a plain text format. Each sketch can be run within the Processing interface using the Sketch → Run command. The Sketch → Tweak command allows you to edit the program code in real-time as the sketch is running. The Sketch → Present runs the sketch as a full-screen application.

Below is an example of Processing code that creates a window that is 640x480 in size and draws a rectangle near the upper left corner that is 300x200 in size.

void setup() {
  size(640,480);
}

void draw() {
  rect(40,40,300,200);
}

Processing is built on Java, so Processing source code has similar syntax to Java. The Processing window is actually a Java program called PApplet, which is a Java class. Before Processing 3 was released (in 2015), it was possible to embed a PApplet into a Java application. The applet dependency was removed in Processing 3.0, so extra code is now required to embed PApplets into Java applications.

While the Processing IDE is the standard way to create and run Processing sketches, they can also be built and run using other interfaces. For example, it is possible to use an IDE like Eclipse as long as Processing's core.jar file is imported. It is also possible to run Processing sketches directly in a web browser using the p5.js JavaScript library. Finally, there is a Processing.py library that allows Processing programs to be written and run in Python.