MAGNETIC DISK DEVICE

PURPOSE:To prevent copying of data by using a part of a data area for an area (reproduction only data area) allowing only a magnetic head having no recording function to access. CONSTITUTION:In a device capable of replacing a magnetic disk, an MR head 2 reproducing a signal from a magnetic disk 20 by the magneto-resistance effect at the inner circumference from an area 10 accessed from a magnetic head 1 capable of recording/reproduction is mounted. No moving function in the disk radial direction is provided to the MR head 2 in such a case, but it is possible to adopt the constitution capable of moving. In shipping the magnetic disk in use while a data is recorded, a data is encoded and recorded in the data area used in the head 1 and the data required to decode the coded data is recorded in reproduction only data area used by the MR head 2. Thus, the copying of information recorded on the magnetic disk is prevented.