Preposition IN Vs Preposition ON when writing by an electronic device

Solution 1:

My name and address database is 'on' my computer, also 'on' my mobile phone. It seems that in all cases where electronic equipment is involved it is 'on'. At least that is the case with me. But I do record some things 'in' a notebook, others 'on' paper. I never write 'on' the wall, though some do, but I have been known to post items 'on' a notice board. Financial data is recorded 'in' a ledger, but sometimes that ledger is held 'on' a computer.

It seems that wherever books are concerned it is 'in', because books can be closed. So I suppose there is a notion of information being inside them.

Solution 2:

It is likely that the convention for storing/writing data "ON" a computer (and not "IN"), derives from the good ol' days when writing to a hard drive actually involved energizing magnetic particles that existed ON the surface of the drive.

http://computer.howstuffworks.com/floppy-disk-drive3.htm

http://www.research.ibm.com/research/gmr/basics.html

Nowadays, the phrase "on a computer" embodies all computer components, including cloud storage which doesn't even physically exist within your electronic device!

It is also not uncommon also to use the phrase "save data TO a computer".