Copy Protection: Key Disk/Tape

One or more of the original game disks or cassette tapes included a mechanism to prevent copying via common commands or utilities; each time the game was played, the original media needed to be available in order to run the program (even if the game was installed to another drive such as a hard disk). The mechanisms to achieve this were varied and ranged from using non-standard sector sizes to using a laser to physically damage a given sector. Generally, the media was formatted in such a manner that could be created by professional disk or cassette duplicators but could not be written using commercially available consumer grade equipment.