Counting

You can also set a variable to a new value using itself, in a sort of feedback loop.
int a=10; a=a+1; println(a); a=a+4; println(a); a=a * 2; println(a); a=a - 40; println(a); a=a+20; println(a); a=150 / a; println(a); a=a*a; println(a);
So, you can use a variable to count:
int a=0; a=a+1; println(a); a=a+1; println(a); a=a+1; println(a); a=a+1; println(a); a=a+1; println(a);
Now see what happens when we add in Processing's draw loop:
int a=0; void setup() { size(500,300); } void draw() { a=a+1; println(a); }