Floppy disk format

DSSoft sectoringdisk formatFMhigh density floppy diskslow-density 3½-inch or 5¼-inch floppiessoft sectorsoft-sectoredSSSS SD
Floppy disk format and density refer to the logical and physical layout of data stored on a floppy disk.wikipedia
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Floppy disk

floppy disk drivefloppy drivediskette
Floppy disk format and density refer to the logical and physical layout of data stored on a floppy disk. SSDD originally referred to Single Sided, Double Density, a format of (usually 5 1⁄4-inch) floppy disks which could typically hold 35-40 tracks of nine 512-byte (or 18 256-byte) sectors each.
There were competing floppy disk formats, with hard- and soft-sector versions and encoding schemes such as FM, MFM, M 2 FM and GCR.

Commodore 8050

80508250SFD-1001
Quad density 5 1⁄4-inch disks were rare, so it was not uncommon to use higher quality double density disks, which were usually capable of sustaining the 96 TPI formatting of quad density, in drives such as the Commodore 8050.
Soft sectoring is used for track alignment.

Floppy disk variants

flippy disksuperfloppiessuperfloppy
Many (but not all) certified "double sided" 8- and 5 1⁄4-inch floppies had an index hole on both sides of the disk sleeve to make them usable as flippy disks.

Double-sided disk

double-sideddouble-sided discdouble sided DVD
*Double-sided disk
* Floppy disk format - explanation of single-sided double-density

IBM Personal Computer

IBM PCPCIBM-PC
In the early 2000s, most floppy disk types and formats became obsolete, leaving the 3 1⁄2-inch disk, using an IBM PC compatible format of 1440 KB, as the only remaining popular format. Single-sided disks began to become obsolete after the introduction of IBM PC DOS 1.1 in 1982, which added support for double-side diskette drives with capacity of 320 KB to the IBM 5150 PC.

Coercivity

coercive fieldmagnetic coercivitycoercive force
Different floppy disk types had different recording characteristics, with varying magnetic coercivity (measured in oersteds, or in modern SI units in amperes per meter), ferrite grain size, and tracks per inch (TPI).

Oersted

megagauss oerstedsOeOERSTEDS
Different floppy disk types had different recording characteristics, with varying magnetic coercivity (measured in oersteds, or in modern SI units in amperes per meter), ferrite grain size, and tracks per inch (TPI).

International System of Units

SISI unitsSI unit
Different floppy disk types had different recording characteristics, with varying magnetic coercivity (measured in oersteds, or in modern SI units in amperes per meter), ferrite grain size, and tracks per inch (TPI).

Ampere

AmAamp
Different floppy disk types had different recording characteristics, with varying magnetic coercivity (measured in oersteds, or in modern SI units in amperes per meter), ferrite grain size, and tracks per inch (TPI).

Cylinder-head-sector

CHScylindercylinders
TPI was not a part of the physical manufacturing process; it was a certification of how closely tracks of data could be spaced on the medium safely.

Modified frequency modulation

MFMFMDelay encoding
Originally, single density and double density indicated a difference in logical encoding on the same type of physical media -- FM for single, and MFM for double.

Group coded recording

GCRgroup-coded recordingGCR (4/5)
GCR was also used on some platforms, but typically in a "double" density form.

Hard sectoring

hard-sectoredhard sectorboundaries of data sectors
8- and 5 1⁄4-inch floppy disks were available with both soft sectoring and hard sectoring.

Optical disc

optical mediaoptical data storageoptical discs
A combination floppy disk and optical disc, known as a Floptical disk exists.

Floptical

A combination floppy disk and optical disc, known as a Floptical disk exists.

Amiga

Commodore AmigaAmiga ComputerAmiga 500/600 (OCS/ECS)
Commodore's Amiga used an unusual format which got closer to the disk's raw (unformatted) capacity by eliminating the gaps between sectors and simplifying the identification data.

File Allocation Table

FATFAT32FAT12
Most floppy disks used by PCs use the FAT12 file system format, which imposes certain practical defaults on the logical geometry in order to be recognizable by all operating systems.

Byte

bytesBTB
SSDD originally referred to Single Sided, Double Density, a format of (usually 5 1⁄4-inch) floppy disks which could typically hold 35-40 tracks of nine 512-byte (or 18 256-byte) sectors each.

IBM

International Business MachinesIBM CorporationInternational Business Machines Corporation
Single-sided disks began to become obsolete after the introduction of IBM PC DOS 1.1 in 1982, which added support for double-side diskette drives with capacity of 320 KB to the IBM 5150 PC.

Disk II

Disk IIc5.25" DrivesApple disk drives
He believed that his simpler design lacked their features, but realized that they were less sophisticated; for example, his could use soft-sectored disks.

Gary Kildall

KnowledgeSetDorothy KildallComputer Connections: People, Places, and Events in the Evolution of the Personal Computer Industry
CP/M's quick success took Kildall by surprise, and he was slow to update it for high density floppy disks and hard disk drives.

CP/M

CP/M-80CP/M operating systemBDOS
IBM System/34 and IBM 3740's single-density, single-sided format is CP/M's standard 8-inch floppy disk format.

Superformatting

format regular floppy disks to 32 MB capacity
Another common use (which is not as popular nowadays) was to format low-density 3½-inch or 5¼-inch floppies as high-density, or in the case of 3.5-inch disks, even extra-high density (HD-36).

Dick Smith Super-80 Computer

Super-80Dick Smith Super-80
The most popular disk format was 5" (133 mm) 80 track, double sided, double density using a Mitsubishi floppy drive mechanism. This gave a formatted disk capacity of 800kB. The UFDC's use of DMA required the VDUEB upgrade to be present. To install the disk controller, the Z80 CPU was removed from the main computer board and installed on the UFDC board. The UFDC then piggybacked on the socket vacated by the CPU. This meant that in theory, the UFDC could be used with almost any Z80 based system, provided there was enough physical space above the CPU. The UFDC used a primitive track based disk operating system called "Super-80 DOS", however a CP/M BIOS later became available.

ALF Products

ALF's Apple Music SynthesizerAD8088 Processor CardALF
The CS5 Turbo system, introduced in 1984, could handle Apple, Atari, Commodore, and TRS-80 disk formats as well as most standard FM 5.25" formats. The CS6 Turbo II system, which used an upgraded controller card, added the popular IBM PC formats and most standard MFM 5.25" formats.