A physical diskette or CD used to help demonstrate a service, software program, software utility, or software game. A demo disc or demo disks offer a free or cheap way for a user to try a program before buying it or signing up. In the picture to the right is an example of an AOL demo disc to try AOL for 1,000 free hours. So many of these discs were received they were often referred to as coasters.
A demo disk may also refer to a diskette or disc that has multiple demos on it. For example, many computer magazines and computer books send demo disks packed full of demos on them. These disks can be very nice as they allow a user not to have to download several hundred megabytes of demos from the Internet.