In the early days of computers, there were no hard disks. The most commonly used data and software storage medium is floppy disk. The first floppy disk was developed by IBM in 197 1 year, with a diameter of 8 inches. With the development of hardware technology and the need of use, 5.25-inch and 3.5-inch floppy disks have been derived and widely used in Apple II, IBM PC and compatible computers.

This data storage method prevailed in the 1980s and 1990s. Until 2000, 3.5-inch floppy disk was still one of the popular computer devices. The popularity of floppy drives and the prosperity of floppy drives, almost all computers are equipped with floppy disks. In other words, floppy disk is the first widely used disk drive.

So you can often see the following information under DOS:

Please insert the source disk into drive a: ...

Please insert the target disk into drive a: ...

Please insert the source disk into drive a: ...

In this way, A was occupied by floppy drive as the first drive letter, and later more computers began to be equipped with a second floppy drive to meet the needs of data replication, so drive letter B was also occupied by floppy drive.

In order to maintain the forward compatibility of the system as much as possible, Windows assigns a drive letter starting with C by default, and this habit has continued until now. In fact, if the current computer is not equipped with a floppy disk drive, you can still force the assignment of drive letters A and B to the hard disk.