History

History

Main article: History of hard disk drives

Hard disk drives were introduced in 1956 as data storage for an IBM real time transaction processing computer^[4] and were developed for use with general purpose mainframe and mini computers.
As the 1980s began, hard disk drives were a rare and very expensive additional feature on personal computers (PCs); however by the late '80s, hard disk drives were standard on all but the cheapest PC.
Most hard disk drives in the early 1980s were sold to PC end users as an add on subsystem, not under the drive manufacturer's name but by Systems Integrators such as the Corvus Disk System or the systems manufacturer such as the Apple ProFile. The IBM PC/XT in 1983 included an internal standard 10MB hard disk drive, and soon thereafter internal hard disk drives proliferated on personal computers.
External hard disk drives remained popular for much longer on the Apple Macintosh. Every Mac made between 1986 and 1998 has a SCSI port on the back, making external expansion easy; also, "toaster" Compact Macs did not have easily accessible hard drive bays (or, in the case of the Mac Plus, any hard drive bay at all), so on those models, external SCSI disks were the only reasonable option.
Driven by areal density doubling every two to four years since their invention, HDDs have changed in many ways, a few highlights include:

• Capacity per HDD increasing from 3.75 megabytes to greater than 1 terabyte, a greater than 270-thousand-to-1 improvement.
• Size of HDD decreasing from 87.9 cubic feet (a double wide refrigerator) to 0.002 cubic feet (2½-inch form factor, a pack of cards), a greater than 44-thousand-to-1 improvement.
• Price decreasing from about $15,000 per megabyte to less than $0.0001 per megabyte ($100/1 terabyte), a greater than 150-million-to-1 improvement.^[5]
• Average access time decreasing from greater than 0.1 second to a few thousandths of a second, a greater than 40-to-1 improvement.
• Market application expanding from general purpose computers to most computing applications including consumer applications