You shouldn't have to unplug your computer in any case. Computers that have automated power management features usually have a push button type power switch. If you press and hold it for (typically) five seconds, the computer will power off.
If you still have the problem, powering off the computer this way isn't a solution, and you'll still have the problem of Scandisk running when you start it up again. But pulling the plug carries a small risk of damaging your hard disks or other spinning media drives, so you should avoid it if possible. Rick Sprague