Potential Problem Areas

The last group of compares illustrate three possibilities for getting into a bit of trouble. All three have the common result that "z" will not get set to the desired value, but for different reasons. In the case of the first one, the compare evaluates as "true", but the semicolon following the second parentheses terminates the "if" clause, and the assignment statement involving "z" is always executed as the next statement. The "if" therefore has no effect because of the misplaced semicolon. The second statement is much more straight forward because "x" will always be equal to itself, therefore the inequality will never be true, and the entire statement will never do a thing, but is wasted effort. The last statement will always assign 0 to "x" and the compare will therefore always be "false", never executing the conditional part of the "if" statement. The conditional statement is extremely important and must be thoroughly understood to write efficient C programs. If any part of this discussion is unclear in your mind, restudy it until you are confident that you understand it thoroughly before proceeding onward.