Backup is the act of copying files to a second medium (a diskette, zip drive or tape) as a precaution in case the first medium fails. You can back up files using operating system commands, or you can buy a special-purpose backup utility. Backup programs often compress the data so that backups require fewer diskettes than the original data.
Even the most reliable computer is apt to break down eventually. Many professionals recommend that you make two, or even three, backups of all your files. To be especially safe, you should keep one backup in a different location from the others.
Many of our jobs today rely on information. If we were to get to work one day and find our offices empty, what would we do about getting work done without any information? All computers, paper files and other information stores gone, such as is possible in case of a fire (remember the Electoral Commission Offices)?