Stack Exchange network consists of 183 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.
Ask questions, find answers and collaborate at work with Stack Overflow for Teams.
Ask questions, find answers and collaborate at work with Stack Overflow for Teams. Explore Teams
Teams
Q&A for work
Connect and share knowledge within a single location that is structured and easy to search.
One can be "on a computer", which means one is using it. In order to do that, one sits at it.
To sit on a computer does actually imply sitting on it.
OED:
on, prep. 3. Indicating the instrument or medium of an action or process.
OED: on, prep. 3. Indicating the instrument or medium of an action or process.