SD Cards and Disk Copy device

SD Cards: A way to use disk related programs with tablets. Cannot be read by computers.

Disk copy device: Can copy or transfer data between disks and SD cards. Transferring will delete the data on the original disk and copying will not.

Currently the disk drive fulfils both these purposes: A disk can be placed into a drive and copied to a computer, then a pocket computer can be placed into the drive and the data can be copied from the computer to it.

Or, with two disk drives attached to the one computer, direct disk to pocket computer transfers are possible.

As for expanding a pocket computer's storage, there are some programs on the forums which allow computers to access files via rednet.