What Happens When You Shut Down a PC - dummies

By Dan Gookin

Sometimes things go wrong when you shut down your PC. If you have to troubleshoot a shutdown issue, it is helpful to understand the shutdown process.

A long time ago, you actually turned a computer off. The console had an on-off switch, and by flipping that switch, you instantly deprived Mr. PC of power, effectively turning the thing off.

Today’s computer comes with power buttons, not on-off switches. Furthermore, you don’t turn off a PC — instead, the thing methodically plods through what’s called a shutdown process.

When you shut down a PC, the following things happen:

A user check takes place: When other users are logged in to the computer (using another account on the same PC), you’re alerted. Do you really want to shut down? Those users may be running programs or have unsaved documents. Clicking No cancels the operation, which is the proper thing to do.

Programs close: Windows shuts down any programs or processes that you’ve begun or that “belong” to you. It sifts through that list and sends every program the shutdown signal. If a program contains unsaved data, you’re prompted to save the data to continue. (Or you can click the Cancel button, which stops the entire shutdown operation.) When a program cannot be stopped, you’re prompted to end it.

Users are logged out: After programs (and processes) belonging to you, the human, are stopped, Windows logs you out, ending your Windows session.

Windows is halted: After you’re gone, Windows begins shutting down bits and pieces of itself. These programs, services, and processes are all ended, and Windows ensures that they end properly and have no social issues or gripes.

The shutdown signal is sent: When Windows is done with itself, it sends a signal to the computer’s power management hardware to turn off the power. If that feature isn’t present, a message appears on the screen, something like It is now safe to turn off this computer and get back to real life.

The shutdown process may seem overly formal. After all, a program stops when it’s told to stop or when the electricity stops. Even though, years ago, computers were routinely shut down by flipping off the power switch, many users found that method unsettling.

By properly shutting itself down, the computer avoids the issue of digital detritus. For example, an improper shutdown causes some programs to leave pieces of themselves lying around like clutter from an explosion. Clutter builds. Rather than deal with the clutter, you should make sure that the tasks the computer does are sanely and systematically shut down.

Another advantage to a proper shutdown is that any looming errors not detected when the computer is running might show up during the shutdown process. Often, that’s the only way to identify and troubleshoot an issue, such as a dead or improperly installed program.