Ever encountered file extensions like "xxx.avi.001" "xxx.avi.002" ?
These are the files which are split by file splitting software like "hjsplit".
You can join them together by using those software, too.
The most common I've seen is "hjsplit" which I mentioned above, and I personally been using it for a long time.
However there are alternatives, too.
Hjsplit - http://www.hjsplit.org/
The Fastest File Splitter and Joiner (FFSJ) - http://www.jaist.ac.jp/~hoangle/filesj/
Both of it offer a "use without install" executable file (Yes, you can translate it as "portable".) And FFSJ even offers a standard version. Look up in their websites for more details.
File splitting are usually useful while you need to share a large file or files over a cloud storage or physical storage. For cloud storage like the famous RapidShare, MegaUpload, FileServe, FileSonic, etc, large files usually give a lot of disadvantages except 'single or fewer link(s)'.
On physical storage side, we know that most usb flash drive are formatted in FAT32, that are not allow for transferring file which are larger than 4GB in size, even if you have a 16GB usb flash drive. Therefore we need to split the file. Of course you can choose to format into NTFS, but it has it disadvantages too, especially on a usb flash drive.
Side note: File archiving software usually has the split file features too. Like the one in 7-Zip.
File Splitting and File Joining can be very fast or very slow depending on the file size and the speed of your CPU.
