[Lua] Read/write files outside of CC working directory?

Is it possible to read a file located at C:\test.txt?
I've been doing some googling + testing but I can't seem to get outside the CC working directory..

No, each computer/turtle is sandboxed so the "root" dir is the numbered directory inside .minecraft/saves/world/computers/

To do otherwise would be a huge security risk. any other players on your server could then just take over your account, and anything it had access to (copy saved passwords, installing trojans, etc)

No, and for good reason.