The conditional clause

The conditional clause behaves pretty much the same way as the conditional expression in a while loop or an if statement.

The expression in the conditional clause is evaluated before the execution of each iteration of the code in the body of the loop. 

(Like the while loop, the for loop is an entry-condition loop.)

If the expression in the conditional clause evaluates to true, the code in the body of the loop is executed once.  Then the update clause is executed and the test in the conditional clause is performed again.

Thus, the code in the body of the loop continues to be executed for as long as the conditional clause evaluates to true.  (Hence the name of the for loop.)

When the conditional clause evaluates to false, the body of the for loop is skipped and control passes out of the loop.