Red Hat® Linux® 7 Unleashed

Basic Concepts of Devices

Devices are either block devices or character devices. A character device is one from which you can read a sequence of characters—for example, the sequence of keys typed at a keyboard or the sequence of bytes sent over a serial line. Character devices are sometimes referred to as sequentially accessed devices. A block device is one that stores data and offers access to all parts of it equally; diskettes and hard disks are block devices. Block devices are sometimes called random access devices.

When you perform some operation on a file, the kernel can tell that the file involved is a device by looking at its file mode (not its location). Different major and minor device numbers distinguishes the device nodes. The major ...