Recording disk cartridge and disk drive

A recording disk cartridge including a recording disk medium and a cartridge case for housing the recording disk medium, comprising:

• a base frame comprising:
• sidewalls of the cartridge case for substantially surrounding a radial directional outside of the recording disk medium and;
• a side opening for exposing the recording disk medium to the outside;
• a lower plate disposed below the recording disk medium for configuring a lower wall of the cartridge case, the lower plate having a center hole for coupling a spindle of a disk drive to the recording disk medium;
• an upper plate disposed above the recording disk medium for configuring an upper wall of the cartridge case;
• a rotary shutter for opening and closing the side opening by a rotation movement thereof within the cartridge case;
• a swing shutter disposed between the recording disk medium and the lower plate and engaging with the rotary shutter for swinging in response to a rotational movement of the rotary shutter to open and close the center hole;
• a chamfer at a corner at a front of the cartridge case in an insertion direction of the cartridge case into the disk drive;
• and
• a function discrimination member disposed at the chamfer for providing discrimination regarding the function of the recording disk cartridge.