dongle-disk

/don'gl disk/ (Or "key disk") A kind of dongle consisting of a special floppy disk that is required in order to perform some task. Some contain special coding that allows an application to identify it uniquely, others *are* special code that does something that normally-resident programs don't or can't.

For example, AT&T's "Unix PC" would only come up in root mode with a special boot disk.