Increment and Decrement Operators

  total = total + 1;     /* increment total */

  total++;              /* increment total */

Pre-increment vs. Post-increment (or ++X vs. X++)

• ++X adds 1 to X.

• X++ adds 1 to X.

• The difference is in WHEN the 1 is added.
  • If the pre-increment operator is being used, as in ++X, X is incremented first and then that new value of X is used in any expression that may be evaluated.
  • If the post-increment operator is being used, as in X++, then the expression is evaluated first (using the value of X), and then X is incremented

--X and X-- work the same way, except 1 is being subtracted from X.

Example:

  x = 3;

  /* prints 4 */
  printf("The value of X is %d\n", ++x);  

  /* and the value of x is now 4 */
  /* prints 4 AGAIN */
  printf("The value of X is %d\n", x++); 

  /* but the value of x is now 5 */

Is all this a good idea?

• It's debatable
• ++ and -- are used a lot
• overuse can lead to obscure code