Order of Operations

When more than one operator appears in an expression the order of evaluation depends on the rules of precedence. A complete explanation of precedence can get complicated, but just to get you started:

1. Multiplication and division happen before addition and subtraction. So 2*3-1 yields 5 , not 4 , and 2/3-1 yields -1 , not 1 (remember that in integer division 2/3 is 0 ).

2. If the operators have the same precedence they are evaluated from left to right. So in the expression iMinute*100/60 , the multiplication happens first, yielding 5900/60 , which in turn yields 98 . If the operations had gone from right to left, the result would be 59*1 which is 59 , which is wrong.

3. Any time you want to override the rules of precedence (or you are not sure what they are) you can use parentheses. Expressions in parentheses are evaluated first, so 2 * (3-1) is 4 . You can also use parentheses to make an expression easier to read, as in (iMinute * 100) / 60 , even though it doesn’t change the result.

Note: Incorrect understanding (usually accidental) of operator precedence is another major cause of logic errors in a program. If there is a chance of misunderstanding, it is a good idea to use parentheses.