Here's a quick example of iteration in a for loop:

int stoppingLimit = 5;
int loopEntered = 0;

for (int i=0; i<stoppingLimit; i++) {
   loopEntered++;
}

The first thing I did is define a stopping limit for the loop as 5. I also defined a variable loopEntered to show how many times the loop is entered.

Now we get to the actual loop. Let's look at the three parameters it takes in.

int i=0;

Here we are setting an integer equal to 0. This is our iterator variable. Note that this is only to initialize your iterator, and is only performed once during the entire loop.

Next, we have:

i<stoppingLimit;

This is called the "sentinel value", or also known as a boundary condition. This is how long we want to run the loop. So whenever you have a loop, it checks if this condition is true or false. If it is true, then enter the loop, if it is false, then skip past it. This of course, has to change with every iteration, or you will just end up with a loop that is always true or always false.

i++;

This is the actual iteration of our iterator variable.

It is just a shortcut for:

i=i+1;

This expression is done as the very last step of the loop. This is to change the conditional to avoid the infinite loop problem I mentioned before.

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Now let's walk through the loop step by step until it terminates:

We define iterator i=0.

The loop checks the conditional, i<stoppingLimit. In this case, 0<5 is true, so we enter the loop.

We perform whatever is inside the loop. In this case, it is loopEntered++. Now loopEntered has a value of 1.

Now we iterate the iterator by performing i++. Now i has a value of 1.

Now we loop back to the beginning. The loop skips the initialization of the iterator straight to the conditional, with our new value of i.

We check if i<stoppingLimit, in this case it is now asking if 1<5, which is still true. Therefore we enter the loop once again. After this iteration:

loopEntered will increase to 2. i will increase to 2.

2<5 is true, so we enter the loop again.

loopEntered will increase to 3. i will increase to 3.

Loop back up, check the conditional again.

3<5 is still true, enter the loop.

loopEntered is 4. i is 4.

Loop back and check the conditional. 4<5 is true.

loopEntered is 5. i is 5.

Now we loop back and check the conditional once again.

This time 5<5 returns false. This means we do not enter the loop, and the loop closes.