C Programming

PRE/POST INCREMENT/DECREMENT OPERATORS
PRE means do the operation first followed by any assignment operation. POST means do the operation after any assignment operation. Consider the following statements


	++count;         /* PRE Increment, means add one to count */
	count++;         /* POST Increment, means add one to count */

In the above example, because the value of count is not assigned to any variable, the effects of the PRE/POST operation are not clearly visible.

Lets examine what happens when we use the operator along with an assignment operation. Consider the following program,


	#include <stdio.h>

	main()
	{
		int count = 0, loop;

		loop = ++count;  /* same as count = count + 1; loop = count;  */
		printf("loop = %d, count = %d\n", loop, count);

		loop = count++;  /* same as loop = count;  count = count + 1;  */
		printf("loop = %d, count = %d\n", loop, count);
	}


	Sample Program Output
	loop = 1, count = 1
	loop = 1; count = 2

If the operator precedes (is on the left hand side) of the variable, the operation is performed first, so the statement


	loop = ++count;

really means increment count first, then assign the new value of count to loop.


Which way do you write it?
Where the increment/decrement operation is used to adjust the value of a variable, and is not involved in an assignment operation, which should you use,

	++loop_count;
or
	loop_count++;

The answer is, it really does not matter. It does seem that there is a preference amongst C programmers to use the post form.


Something to watch out for
Whilst we are on the subject, do not get into the habit of using a space(s) between the variable name and the pre/post operator.

	loop_count ++;

Try to be explicit in binding the operator tightly by leaving no gap.


ęCopyright B Brown. 1984-1999. All rights reserved.