At some point in your affair with computers you will have to transport your files from your friendly home computer to a foreign, possibly weird, one. Since there are a number of electronic networks in place, once you read your files onto any computer either at home or away, you may be able to transfer it to another computer-and possibly the foreign one no less. This is the best way to transfer files, and we talk about it in Chapter 3, Computer-Computer Interactions. Transferring your files electronically after you arrive at your foreign host may be possible (and necessary since you're bound to have forgotten something or taken the wrong version). However, this may not be reliable for very large files. If you plan to make electronic transfers after you leave home, you need a system at home with which you can communicate (e.g., with the file transfer protocol ftp or kermit or via remote login); you will need your files in a form which you can access without your being there, not just stored on backup tapes; and you may need a friend at home who knows your hiding places for backups and will turn your computer on as needed.
If you can't transfer your files electronically, or if you want to be sure, you should transport your files on more than one medium, e.g., on both floppy diskettes and cartridge tapes. The tape archive command tar (to be discussed soon) produces files on differing media in a format that is easy to understand and (nearly) universal. While we will see it is easy enough to load many files onto a particular type of cartridge tape or a high density floppy, for this to be useful there must be a matching drive at the foreign site able to read them. You will have a better chance for success if you write the tape or floppy from a computer system at home which is the same or similar to the foreign one and if you check before leaving home that the tape or floppy can be read.
To avoid the possible disasters, we suggest the following: