A 5.25" disk drive that measures 3.25" in height. It was the size of first-generation drives in desktop computers, which had either two floppy drives or one floppy and one hard drive. When half-height drives came out, a full-height bay could hold two half-height drives. Contrast with half-height drive
CP/M computers in the early 1980s had two full-height drives. When hard drives were introduced, they started out at 5MB. Today's entry-level smartphone has 3,000 times as much storage.