What happens from the moment we press a key on the keyboard, until it appears in your word document

1. you hear a click ;) [but not necessary at this step, maybe at 10th or 20th]
2. keyboard signals to kb controller
3. controller issues an interrupt to CPU
4. OS kernel sees interrupt
5. OS kernel dispatches interrupt to corresponding driver
6. driver tells CPU to read a charcode from kb controller
7. CPU does
8. driver some way tells the kernel to post an 'KEY_DOWN' event into UI subsystem
9. kernel dispatches event
10. UI subsystem checks if there active window
11. it sends a KEY_DOWN UI event to active window

... uh.. tired :) so, after that it will dispatch a key, update window contents, and call the video driver/subsystem to draw that char