Lexikon's History of Computing

Early Floppy Diskette Types

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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.


Floppy Disk Type



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



3.5 inch Micro Floppy, Double Density

720 K

Hard plastic case


3.5 inch Micro Floppy, High Density

1.44 Mb or

2.88 Mb

Hard plastic case

See also Floppy Diskette Brands

See also Large IBM Storage Disk

Storage Disks Compared


Copyright © 1982-2001, Lexikon Services "History of Computing" ISBN 0-944601-78-2