What happens when you press two keys on the keyboard at the same time?

[Crafty]

Hi, I have just purchased this keyboard modification for my flight Sims, but I am a unsure how this will work because some keys are modified to be pressed at the same time. I would like to know what happens when you press some keys together on a keyboard before I start to mess about doing this. Please look at the link below and you will see the modifications they use on the keyboards. I realise you can press some key combinations using shift, Ctrl etc, but these ones look different so take a look before commenting. Thanks!!

http://www.rogerdodger.net/diyflightsims/keyboard_home.html

[quaxo]

You can press key combinations of any keys, especially when playing games. In some cases, you might be limited to how many keys you press at the same time (2, 3, or 4 keys) but they can still be pressed together. How a program reacts to these presses is entirely up to the program. For typing, if you press and hold a combination of keys, it will show all keys in the order they were pressed, but only repeat the last key to make contact (it's humanly impossible to make them all contact at the exact same time). For example, if I attempt to press ASDF all at the same time, I get something like this: adfssssss, with 's' being the last key to make contact.

In games, key combinations are a normal thing. For example, if playing a first person shooter, you might have your movement keys mapped to WASD, space for jump, F to open/use things, and R to reload. If I am holding W to move forward, then press space to jump over something, R to reload, without releasing any of the keys, all actions should happen simultaneously. You should be only limited to the number of keys you can have pressed at one time.

[Geek-9pm]

The standard keyboard on a PC generates a code for each key press, even for keys that do not make anything visible in a text document. For example, the right shift and left shift each produce their own special codes when pressed and when released.Thus it is possible to strike a normal letter and the shift at the almost same time and the software knows exactly that you did press the shift first. But if you press two letter keys at the same time, the built in decoder can not always determine which to keys wee pressed. But most of the time it can. The decoder is extremely fast at the lowest level. It is the layer upon layer of software filters that can make keyboard response time slow. Reading the keyboard directly, at the lowest level, results in times measured in milliseconds.
http://computer.howstuffworks.com/keyboard3.htm