In the early days of DOS, the PC's storage device did not have any CD-ROM drives and U disks, with dozens of MB or hundreds of MB hard drives. And that's OK. Some earlier computers, such as 8086, 4004, and 8088 (CPU) computers, don't even have a hard disk. The storage devices at that time were mostly floppy disks.
The floppy disk is divided into two kinds, one is a 5 inch large floppy disk, and the other is a 3.5 inch floppy disk. Of course, they correspond to a 5 inch floppy drive and a 3.5 inch floppy drive.
5 inch floppy disk
3.5 inch floppy disk
These two kinds of relatively large floppy disk in the floppy disk earlier, and the system must give it a letter, so modern PC inventors naturally use alphabet initials A, named B A:\ B:\ is the name of the floppy drive;
How do you understand? Basically you can understand the C early computer is the most front drive. The rapid development of computer technology, Windows operating system is extended by the original DOS under the set habit, put these two letters to the floppy drive. If you are installing a floppy drive, it is the natural A or B.
Of course, the floppy drive has become the past, but the 2 letters but this system left behind, like a tribute to the spirit of the computer technology always stay on......
So, you see? End of science popularization.