Conditions are like questions. They allow a program to decide to take one action if the answer to a question is true or to do another action if the answer to the question is false. The questions asked within a program are always logical or relational statements. For example, if the variable 'i' is equal to zero then draw a line.

Original Example: Conditionals1

// All Examples Written by Casey Reas and Ben Fry
// unless otherwise stated.
size(200, 200);

for(int i=10; i<width; i+=10) {
  // If 'i' divides by 20 with no remainder draw the first line
  // else draw the second line
  if(i%20 == 0) {
    line(i, 40, i, height/2);
  } else {
    line(i, 20, i, 180);