SOFTWARE COPY PROTECTION BY CONTROLLED DAMAGE.

Unauthorized copying of programs on a magnetic disk is prevented by physically damaging some portion of the disk so that such area will not record any data. Attempts to read such damaged area always produce the same result regardless of any attempts to write in the damaged area. A routine is included within the program software to write and read at the damaged area. If the read pattern matches the written pattern, then the disk cannot be the original, but rather must be a copy of the original.