Split Byte is a tool for breaking large files into smaller segments for easier handling, then rejoining them at some later date.
This can be very useful if you need to work with a particularly large file: a multi-gigabyte video, say. It'll be too large to email, perhaps even save to CD or DVD, but if you use Split Byte to separate the file into chunks then it'll become much more manageable.
The core of the program is very straightforward. Point Split Byte at your file, choose the number of chunks you need (or the maximum chunk size), click Split, and you're done - the program will divide up the file on your behalf.
But there are also lots of additional features. You can choose to zip up the file before splitting, for instance; the program can encrypt your file, useful if it contains confidential data; you can even have the chunks sent via email when you're done.
Joining is similarly straightforward (point the program at the first chunk and it'll figure out everything else on its own).
And you even get an MD5 Checksum calculator to confirm that the split and join operations haven't corrupted the file (that is, it's the same).
Please note, by default the program will install a browser addon. If that's not what you want, be sure to choose the "Custom Setup" option during installation, and clear the relevant checkboxes. Then click "Decline" on any subsequent add-on related dialogs which might appear.