File Spanning is the ability to package a single file or data stream into separate files of a specified size. This task implies the ability to re-combine the package files back into the original file or data stream.
This is useful when saving large files onto smaller volumes or breaking large files up into smaller files for network messages of limited size (email, newsgroups). It also allows the creation of parity files such as parity archive (PAR) to verify and restore missing or corrupted package files.
Sometimes the file spanning process is hidden as a secondary operation such as with file archivers. In this case, many smaller files are first packaged into a data stream and then repackaged into a multi-file archive.
File Spanning Software 
Hundreds or thousands of file spanning utilities are available for nearly every OS and platform. Below are a few examples: