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(詳細はfloppy disk is a disk storage medium composed of a disk of thin and flexible magnetic storage medium, readable by a floppy disk drive (FDD), and sealed in a rectangular plastic carrier lined with fabric which serves the purpose of keeping the data storage disk free of foreign particles such as dust.〔(【引用サイトリンク】title=IBM Floppy Disk )〕 The floppy disk was a revolution in the computer industry when it was developed by IBM in the late 1960s as a reliable and inexpensive method of loading microcode into their System/370 computer. Floppy disks remained a popular portable digital-storage medium for nearly 40 years after being introduced commercially in 1971. Throughout the period in which floppy disks were common, they went through numerous improvements, each time significantly improving their available storage capacity and reducing their physical size as computer data storage technology advanced. Sizes ranged from 8 inches in the first commercialized floppy disk to the 3½-inch floppy disks still available today. Floppy disks slowly lost popularity as better technology developed which was able to offer higher levels of storage capacity, smaller physical characteristics, and faster processing speeds. While floppy disk drives still have some limited uses, especially with legacy industrial computer equipment, they have been superseded by data storage methods with much greater capacity such as USB flash drives, portable external hard disk drives, optical discs, memory cards, and computer networks. == The 8-inch disk == In 1967, IBM tasked their San Jose, California storage development center to develop a reliable and inexpensive system for loading microcode into their System/370 mainframes in a process called Initial Control Program Load (ICPL). The System/370 was IBM's first computer system family to make extensive usage of volatile read/write semiconductor memory for microcode,〔The Model 85 of System/360 used a mixture of non-volatile Capacitive Read Only Storage and volatile semiconductor memory; however the latter was mainly used for emulation, microdiagnostics and some low cost features 〕 so for most models, whenever〔Except for the 155, 155 II, 165, 165 II and 195.〕 the power was turned on, the microcode had to be loaded (System/370's predecessor, System/360, generally used non-volatile read-only memory for microcode). IBM also wanted inexpensive media that could be sent out to customers with software updates.〔 〕 IBM Direct Access Storage Product Manager, Alan Shugart, assigned the job to David L. Noble, who tried to develop a new-style tape for the purpose, but without success. Noble's team developed a read-only, flexible diskette they called the "memory disk", holding 80 kilobytes of data. The original disk was bare, but dirt became a serious problem so they enclosed it in a plastic envelope lined with fabric that would remove dust particles. IBM introduced the diskette commercially in 1971.〔http://www-03.ibm.com/ibm/history/exhibits/storage/storage_chrono20.html〕〔A Japanese inventor, Yoshiro Nakamatsu, claims to have invented core floppy disk technology, and in 1952, registered a Japanese patent for his (invention ). He further claims to have later (licensed ) 16 patents to IBM for the creation of the floppy disk. However, there is no evidence independent of Dr Nakamatsu's assertions that supports these claims.〕 The new device, developed under the code name Minnow first shipped in 1971 as the 23FD, the program load component of the 2835 Storage Control Unit.〔(IBM Archives: IBM 2305 fixed head storage )〕 and then as a standard part of most System 370 processing units and other IBM products. Internally IBM used another device, code named Mackerel, to write boot disks for distribution to the field. Alan Shugart left IBM and moved to Memorex where his team shipped the Memorex 650 in 1972, the first commercially available read-write floppy disk drive. The 650 had a data capacity of 175 kB, with 50 tracks, 8 sectors per track, and 448 bytes per sector. The Memorex disk was "hard-sectored", that is, it contained 8 sector holes (plus one index hole) at the outer diameter (outside data track 00) to synchronize the beginning of each data sector and the beginning of a track. In 1973, IBM shipped its first read/write floppy disk drive, the 33FD, as a component of the 3740 Data Entry System,〔(IBM Archives: IBM 3740 )〕 code named "IGAR", designed to directly replace IBM's punched card ("keypunch") data entry machines. A significant feature of IBM's read/write disk media was the use of a Teflon-lubricated fabric liner to lengthen media life. In 1976, media supplier Information Terminals Corporation enhanced resilience further by adding a Teflon coating to the magnetic disk itself.〔(40 years of Verbatim: From garage to global leader in storage. )〕 The new system used a different recording format that stored up to 250¼ kB on the same disks. Drives supporting this format were offered by a number of manufacturers and soon became common for moving smaller amounts of data. This disk format became known as the Single Sided Single Density or SSSD format. It was designed to hold just as much data as one box of 2000 punch cards. The disk was divided into 77 tracks of 26 sectors (a total of 2002 sectors), each holding 128 bytes. When the first microcomputers were being developed in the 1970s, the 8-inch floppy found a place on them as one of the few "high speed, mass storage" devices that were even remotely affordable to the target market (individuals and small businesses). The first microcomputer operating system, CP/M, originally shipped on 8-inch disks. However, the drives were still expensive, typically costing more than the computer they were attached to in early days, so most machines of the era used cassette tape instead. Also in 1973, Shugart founded Shugart Associates which went on to become the dominant manufacturer of 8-inch floppy disk drives. Its SA800 became the industry standard for form factor and interface. In 1976, IBM introduced the 500 KB Double Sided Single Density (DSSD) format, and in 1977 IBM introduced the 1–1.2 MB Double Sided Double Density (DSDD) Format.〔(Five decades of disk drive industry firsts ), DISK/TREND, Inc., publisher of market studies of the worldwide disk drive and data storage industries. web.archive.org〕 Other 8-inch floppy disk formats such as the Burroughs 1 MB unit failed to achieve any market presence. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「History of the floppy disk」の詳細全文を読む スポンサード リンク
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