5.25 inch floppy disk
The successor to the 8 inch floppy, this format was specifically made for use in home computers. The first IBM PC originally shipped with 160kb single-sided single density drives, but these were quickly replaced with 360kb single-sided double density drives with the PC-XT and later model 5150s. Quad density 720kb 5.25" drives do exist, but never really caught on in the personal computer industry. The last popular 5.25" drive was the double-side double density 1.2mb introduced with the IBM AT in 1984. Both the 1.2mb and 360kb formats were popular for most of the 1980s, and as the two were not fully compatible it was common practice for AT type systems to come with both drives. 1.2MB drives could read 360kb disks, but they could not write them in a way that a real 360kb drive could read them reliably. The 5.25" format was superseded by the 3.5 inch floppy format, but was still popular as a second drive until around 1993 when CD-ROMs started to become mainstream.