Easy. You put the whole cartridge in. The drive takes two cartridges and three loose disks. I seem to recall that the OS accepted designations for either cartridge, both cartridges, any single disk, or all three single disks, and there may have been a way of specifying a single disk within a cartridge (I can look this up at home). In all cases except a single disk specified, when the machine got to the end of a disk, it would spit the disk back out into the cartridge (or disk slot), move the disk carriage up one space, and suck another disk into its innards to read or write it. A sort of jukebox mechanism, I suppose. I also recall it was pretty speedy, something like 4 cylinders a second, 20 seconds to read or write a whole diskette. Philip.