Engineers at Shugart Associates unveiled the 5.25-inch flexible disk drive, designed after executives reportedly sized the format against a cocktail napkin at a bar. The smaller, cheaper format became the standard storage medium for early personal computers throughout the late 1970s and 1980s, enabling the home computer boom.
The legend, repeated by Shugart Associates founder Alan Shugart himself, is that the 5.25-inch disk's dimensions were sketched out during a conversation at a hotel bar, with a napkin held up against a drink to gauge the right size. Whether or not the napkin story is literally true, the format that emerged was deliberately smaller and cheaper than the unwieldy 8-inch floppy disks used in minicomputers and word processors.
An Wang of Wang Laboratories had asked Shugart to build a more compact drive, and the resulting 5.25-inch disk, formally introduced this day, held around 110 kilobytes in its earliest form. It seems almost comically small by later standards, but it was revolutionary for machines like the Apple II and early IBM PCs.
The format's low cost and improving capacity made it the backbone of the emerging personal computer industry, and it wouldn't be displaced until the sturdier 3.5-inch disk arrived in the following decade.