WORM Disk

A 'Write Once Read Many' non-magnetic disk where, once data had been written to the disk, it could not be deleted, changed, or any more data added, but could be read, or copied to other media, as many times as required. Users of early CD drives used this technique to 'burn' programs and/or data onto a CD for distribution in the knowledge that it could not be altered in any way but was more reliable than removable magnetic media in situations where the disk would be accessed frequently.

Although advances in CD technology mean that in some cases more material can be added, and, most recently, can be deleted and the disk re-used, WORM disks are still the standard medium for distributing commercial software, and for companies distributing static data.