FloppyDisketteTypes

Lexikon's History of Computing

Early Floppy Diskette Types

In 1971, Alan Shugart led a team at IBM that developed the 8 inch floppy diskette for data and program storage.

In 1976, IBM introduced the 5-1/4 inch diskette.

In 1981, Sony introduced the 3.5 inch diskette, which was a floppy disk inside a hard plastic case.

The densities of the diskettes varied depending on how the diskette was formatted. Early diskettes often came unformatted. Later, pre-formatted diskettes became the norm. You need to look at the label of a formatted diskette to determine what density it has.

Abbr.	Floppy Disk Type	Capacity	Info
SS/SD or 1S/1D	Single Sided, Single Density	100 K	First generation. Capacity varies
SS/DD or 1S/2D	5-1/4 inch Single Sided, Double Density	180 K
DD/DD or 2D/2D	5-1/4 inch Double Sided, Double Density	360 K	Most common type in the early 1980's
DD/HD or 2D/HD	5-1/4 inch Double Sided, High Density	1.2 Mb
DD	3.5 inch Micro Floppy, Double Density	720 K	Hard plastic case
HD	3.5 inch Micro Floppy, High Density	1.44 Mb or 2.88 Mb	Hard plastic case

See also Floppy Diskette Brands