The history of floppy drives started with the first 8-inch (~203 mm) floppy drive, introduced in 1970. It was replaced by the 5.25-inch (133 mm) drive in 1976 and by the 3.5-inch (89 mm) “micro-floppy” in 1980. Initially, the floppy drive was single-headed (one-sided) and had a storage capacity of 322 KB. The disk was protected by a hard plastic jacket, which increased its durability and made handling easier. Gradually, the drive became dual-headed (double-sided) and eventually reached today's 1.44 MB capacity (2 MB unformatted). The drive's height also decreased from an initial 51 mm to 25 mm. Table 3-8 summarizes typical characteristics of a 1.44 MB micro-floppy disk drive.