 Hard disk drives for personal computers (PCs) were initially a rare and very expensive optional feature; systems typically had only the less expensive floppy disk drives or even cassette tape drives as both secondary storage and transport media.However by the late '80s, hard disk drives were standard on all but the cheapest PC and floppy disks were used almost solely as transport media.Most hard disk drives in the early 1980s were sold to PC end users by systems integrators such as the Corvus Disk System or the systems manufacturer such as the Apple ProFile.