In all structured loops, the loop-controlling question provides the only entry to, or exit from, the repeating structure. The body of a loop can contain only a limited number of statements. You can use a while loop to execute a body of statements continuously as long as some condition continues to be false. A loop control variable's value is tested to control the loop's execution. If you use the wrong comparison with the loop control variable, the body of the loop may never execute. A while loop can be used to code both definite and indefinite loops. There is no benefit to changing a variable's value when it will never be used again during the current execution. If a data item is valid, this also means that it is correct. An error commonly made by beginning programmers is to forget that array subscripts start with the integer 1. Each variable within an array has the same name and the same data type. A flag is a variable you set to indicate whether some event occurred. Parallel arrays are two arrays such that each element in one array is associated with the element in the same relative position in the other array. As with a while loop, when you use a for loop, you must be careful to stay within array bounds, remembering that the highest usable array subscript is one less than the size of the array. A method cannot be used more than once within a program or in other programs. The three parts of a method are the method's header, the method's body, and the method's return statement. In a flowchart, you draw the main () method and every other method separately with its own sentinel symbols