Flippy disk was a nickname given to single-sided floppy disks that had a second write-enabled notch cut into the sleeve so that the second side could be written to by a single-sided disk drive. Generally, these were 5.25-inch minifloppy disks, but 8-in
When the 5.25-inch floppy disk was introduced in 1976, all drives were single-sided. Double-sided drives were introduced in 1978, but suffered from early reliability problems. It wasn't until 1982 that double-sided drives were supported by IBM PC-DOS i
The second write-enabled notch could be made by hand, or special 'disk doubler' rectangular hold puncher could be bought to do the job. Flippy disks were also sold ready-made, and software was distributed on flippy disks that might have different progr