Iteration with a "for" structure constructs repetitive forms.
Original Processing.org Example: Iteration
// All Examples Written by Casey Reas and Ben Fry // unless otherwise stated. int k; int xpos1 = 100; int xpos2 = 118; int count = 0; int timey = 0; int num = 12; size(200, 200); background(102); noStroke(); // Draw gray bars fill(255); k=60; for(int i=0; i < num/3; i++) { rect(25, k, 155, 5); k+=10; } // Black bars fill(51); k = 40; for(int i=0; i < num; i++) { rect(105, k, 30, 5); k += 10; } k = 15; for(int i = 0; i < num; i++) { rect(125, k, 30, 5); k +=10; } // Thin lines k = 42; fill(0); for(int i=0; i < num-1; i++) { rect(36, k, 20, 1); k+=10; }