Reference for Processing version 1.2. If you have a previous version, use the reference included with your software. If you see any errors or have suggestions, please let us know. If you prefer a more technical reference, visit the Processing Javadoc.



float yPos = 0.0; 

void setup() { 
  size(200, 200); 
void draw() { 
  yPos = yPos - 1.0;
  if(yPos < 0) {
    yPos = height;
  line(0, yPos, width, yPos);

void setup() {
  size(200, 200);

void draw() { }

void mousePressed() {
  line(mouseX, 10, mouseX, 90);
Description Called directly after setup() and continuously executes the lines of code contained inside its block until the program is stopped or noLoop() is called. The draw() function is called automatically and should never be called explicitly. It should always be controlled with noLoop(), redraw() and loop(). After noLoop() stops the code in draw() from executing, redraw() causes the code inside draw() to execute once and loop() will causes the code inside draw() to execute continuously again. The number of times draw() executes in each second may be controlled with the delay() and frameRate() functions. There can only be one draw() function for each sketch and draw() must exist if you want the code to run continuously or to process events such as mousePressed(). Sometimes, you might have an empty call to draw() in your program as shown in the above example.
draw() {
statements A sequence of statements
Returns None
Usage Web & Application
Related setup()
Updated on June 14, 2010 12:05:29pm EDT

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