- you hear a click ;) [but not necessary at this step, maybe at 10th or 20th]
- keyboard signals to kb controller
- controller issues an interrupt to CPU
- OS kernel sees interrupt
- OS kernel dispatches interrupt to corresponding driver
- driver tells CPU to read a charcode from kb controller
- CPU does
- driver some way tells the kernel to post an 'KEY_DOWN' event into UI subsystem
- kernel dispatches event
- UI subsystem checks if there active window
- 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