A disk cartridge, which is easy to handle, is provided. The disk cartridge
includes a cartridge main body having: an opening facing a disk; and a
shutter for opening and closing the opening. A part of the cartridge main
body is formed in an approximately semicircular shape. Such a shape
allows a user to easily know an insertion direction. Moreover, since the
cartridge main body does not have any corners, the insertion into a drive
device is simplified. The shutter is provided pivotably for the cartridge
main body. Any one of a plurality of types of medium can be provided in
the disk cartridge. When the disk cartridge is inserted into an external
device such as the drive device, the device receives a signal indicating
the type of medium, which is transmitted through an electric terminal, so
as to perform a process in accordance with the type of medium.