Why can't I use two or more keyboards/mice at the same time on one computer?

Solution 1:

Parallel, simultaneous use of multiple input devices on one computer is technically possible, but not widely supported because there is lack of demand. It would require extra software developer time to design, test, and maintain such a feature. Most software companies, including Microsoft, choose to devote developers' time to other features that are more in demand.

However, some companies decide it is worth putting in the extra effort. Mouse Party is an example of software that supports up to 9 mice pointers simultaneously on one computer:

Now with Reflexive’s Mouse Party™ , UP TO 9 PLAYERS AT ONCE can play a video game - simultaneously ON THE SAME COMPUTER!

Each Reflexive game featuring the Mouse Party logo (LOGO) supports this unique play mode where multiple people can gather around the same PC and play cooperatively or competitively with the other players.

Ready to liven up a get together, or have a little friendly competition to see which of your family members gets a night off from doing the dishes? Mouse Party is just the ticket!

Note: I was originally thinking of a different game that supported "party-mode" mice (perhaps the first one to do so?), but couldn't find it. It was released several years ago. I think each player controlled their own pirate ship. Anyone else remember this game?

Solution 2:

No OS that I know of supports two independent cursors, or keyboard inputs to the same session.

Microsoft does however support two (or more) different users sessions on one PC. It's called Windows Multipoint and is aimed at medical and educational situations, but could work anywhere really. This allows a PC to have two keyboards, mice, and screens at the same time; and the sessions on the screens are independent.

HP makes a MS 6000 desktop that does this, and T100 modules to plugin additional stations. You can add quite a few additional stations if the workload is very light.

X can already do this sort of thing by setting up two different X servers with different configurations (for the screen, keyboard, and mouse).