When you sit in front of a computer and the screen saver is active and not password-protected, all you have to do to deactivate the screen saver is to move the mouse or hit a keyboard key. Well, I believe that, more often than not, the safer of the two options is to move the mouse.
Granted, if you press a key, your key press will usually be “absorbed” and will not be passed on to the foreground application, if there is one. But that really depends on the particular screen saver, since the screen saver is in itself an application. So, anything goes. It is best to know how the particular screen saver functions, but sometimes you have to deal with a screen saver that is unknown to you.
Most screen savers “absorb” all key strokes until they fully deactivate themselves, so none of the key strokes are passed to the foreground application underneath them. The blank screen saver is a notable example. Of course, after any screen saver is deactivated, all subsequent key strokes are passed to the foreground application.
There are screen savers that deactivate so quickly that only the first key press is blocked and all subsequent key presses pass through. So what happens if there is a foreground application window behind such a screen saver and your finger slips and presses the key twice rather than once? In such a case, the application will receive the second key press.
Now depending on the application, the state it is in and the particular key that you happened to press twice, the effect might be from insignificant to, well, not so insignificant.
The Enter key is dangerous in such a situation. But so is Esc, since it cancels a dialog box. Esc can also close an application like Task Manager. And if a button has the focus, pressing the spacebar is the same as clicking on the button. The spacebar also changes the status of a checkbox that has the focus. This in and by itself is not dangerous. What might be dangerous is that you might not be aware of the change in the checkbox. And what about the arrow keys? They too can be dangerous, especially the up arrow which can bring up the previous command in a command prompt. Then all that is left is for Enter to be pressed and the command will be run again. A letter can also be unwanted, depending on the situation.
There are keys that are generally less dangerous, like Shift. So, if by moving the mouse you get no result (if, for example, there is a problem with the mouse), you could try hitting a key, but choose wisely.
There is also another reason you should usually prefer moving the mouse over hitting a key. Sometimes there is no screen saver set, but the monitor is set to turn off in a specified number of minutes. So, if you are not careful, you might mistake a monitor on stand by mode for an active monitor with a blank screen saver.
The difference is important. A monitor on stand by appears black and a key press will turn it on, but the key press will also be passed on to the foreground application, a thing that, as I explained, might be dangerous. Instead, if we have an active monitor with a blank screen saver, the key press will deactivate the screen saver, but the key press will not be passed to the foreground application. So, by just moving the mouse, you are better off, without having to check which of these two cases you are dealing with.
Of course, depending on your situation, it may be important for you to preserve the position of the mouse pointer. If this is the case, then you should certainly use the keyboard instead of the mouse to deactivate the screen saver.
OK, enough work, now let’s have some fun. Here is how you can play a practical joke on a friend.
At first you begin by telling her that you want her to help you research a topic that has been troubling you: whether or not screen savers “absorb” or pass through the key press. If your friend knows the answer, she will tell you that the key press is not passed on to the foreground application, otherwise she will be interested in finding out. In any case, you will ask her to help you prove or research the topic.
So you will go to a computer and with the help of your friend set a screen saver (other than the blank screen saver) to activate after 1 minute, in order to be able to produce quick results. And then you will open an application. Let her choose whatever she likes. Or you could suggest Notepad, Task Manager, a command prompt, a dialog box, whatever.
Leave the computer be for 1 minute and when the screen saver is active, let your friend press a key and watch as she proves or finds out that the key press is not passed on to the foreground application. Do a few more experiments and then declare that you are convinced of the results.
Now the next day, before your friend arrives, go to the same computer, set the screen saver to “None” and also set the power settings so that the monitor is turned off after 1 minute.
When your friend arrives tell her that you experimented a bit more and found that the key press passes through when a blank screen saver is used. This is, of course, a lie. In fact, quite the opposite is true. As I explained, the blank screen saver “absorbs” all key strokes until it deactivates.
Your statement will puzzle your friend and she will want you to show her. Take her to the computer and move the mouse so the monitor will turn on, but let her get the wrong impression that the computer has a blank screen saver. Let your friend arrange the application she chose as before, and then take her away from the computer. Remain with her constantly so that she will feel that she controls every aspect of the test.
Then after 1 minute take her again to the computer and ask her to press a key. Chances are that she will mistake the turned off monitor for a blank screen saver, since all the tests you have been conducting the day before were about screen savers and nothing was mentioned about monitors in stand by mode. It will also help if you speak to her at this moment, in order to distract her from noticing too many details.
Anyway, she will press the key she chooses and she will then see the effect of the key press passing through to the foreground application. If this will puzzle her, you will have succeeded in deceiving her. You can let her perform another test, if she likes. Let her reflect on that a little and then reveal the truth to her.
I want to finish this tip with two requests. First of all, you have a moral obligation to reveal the truth to your friend at the end. Under no circumstances should you let her leave having the wrong impression. I know, I know. Magicians never reveal their tricks. But we are not magicians. Don’t quit your day job just yet. And second, please realize that playing practical jokes like this is the easiest way to loose a friend and for people to dislike you. For this or any other practical joke choose a friend that you know will not be offended. The best choice is usually a friend that she and you are constantly playing practical jokes on each other.