Short for drive bay, this refers to a site in a personal computer where a hard or floppy disk drive, CD-ROM drive or tape drive can be installed. Thus, the number of drive bays in a computer determines how many mass storage devices can be internally installed.
For PCs, bays come in two basic sizes: 3.5-inch and 5.25-inch, which represents the bay’s height. In addition, bays are described as either internal or exposed. An internal bay cannot be used for removable media, such as floppy drives. Some manufacturers use the terms hidden and accessible in place of internal and exposed.
Don’t confuse bays with slots, which are openings in the computer where expansion boards can be installed.