Abstract: A cassette library (1) is provided with a driving apparatus (13), cassette housing shelves (14, 15) and a cassette carrier (16). A library controller (2) simulates as if driving apparatuses (13) having continuous address numbers were apparently used in the host computer (3) even when physically discontinuous address numbers are allocated to the driving apparatus (13), thereby making it possible to set occupancy for a driving apparatus with an arbitrary address number. The library controller (2) has the cassette carrier (16) automatically carry, at a preset timing, a cleaning cassette from the cassette housing shelf (14, 15) to the driving apparatus (13) to clean a recording reproduction head of the driving apparatus (13) using the cleaning cassette which is then carried back to the housing section in the original cassette housing shelf (14, 15) after the cleaning work.

Abstract: A recording device for recording information upon optically modulated overwritable magneto-optical recording medium including four magnetic layers first records DC "1" and then a test signal at high and low recording laser power levels upon a test track of the recording medium. The high and low recording laser power levels are successively modified to scan a two-dimensional region of the high and low recording laser power levels, and the optimal high and low recording laser power levels are determined on the basis of the reproduction signal levels corresponding to respective combination of high and low recording laser power levers. The reproduction signal levels are represented upon the .alpha.-K plane which is divided into six characteristic regions, The optimal combination of high and low recording laser power levels is determined as a representative point within the region of correct reproduction with a predetermined allowance.

Abstract: A floppy disk has a magnetic disk (1) accommodated in a casing provided with a head insertion opening. When cleaning the floppy disk, air in the casing is sucked through the head insertion opening while the magnetic disk is rotated and ionized air is blown toward the disk surface through the head insertion opening. An ionizing needle (13) ionizes the air before it hits the disc (1). Suction nozzles (12a and 12b) suck air away from the disc.

Abstract: A magneto-optical recording process is produced by irradiating a recording track of a recording medium, in the course of movement thereof, with a main light beam of intensity sufficient for heating the medium to a temperature at which the coercive force thereof is reduced to zero or a very small value in a continuous manner during the recording operation and irradiating a separating area with a subsidiary beam of a modulated intensity, thereby modulating the vertical magnetization of said separating area. A floating magnetic field generated by the thus modulated vertical magnetization generates magnetic fields of mutually different directions, thus forming a record bit on the recording track.