This example is for Processing 2+. If you have a previous version, use the examples included with your software. If you see any errors or have suggestions, please let us know.

Iteration.

Iteration with a "for" structure to construct repetitive forms.

 
int y;
int num = 14;

size(640, 360);
background(102);
noStroke();
 
// Draw gray bars 
fill(255);
y = 60;
for(int i = 0; i < num/3; i++) {
  rect(50, y, 475, 10);
  y+=20;
}

// Gray bars
fill(51);
y = 40;
for(int i = 0; i < num; i++) {
  rect(405, y, 30, 10);
  y += 20;
}
y = 50;
for(int i = 0; i < num; i++) {
  rect(425, y, 30, 10);
  y += 20;
}
  
// Thin lines
y = 45;
fill(0);
for(int i = 0; i < num-1; i++) {
  rect(120, y, 40, 1);
  y+= 20;
}