Most devices in Linux are represented by device nodes, in accordance with the Unix philosophy that everything is a file (except network interfaces, which are sockets). A device node may refer to a block device or a character device. Block devices are mass storage devices such as SD cards or hard drives. A character device is pretty much anything else, once again with the exception of network interfaces. The conventional location for device nodes is the directory
/dev. For example, a serial port may be represented by the device node
Device nodes are created using the program
mknod (short for make node):
mknod <name> <type> <major> <minor>
name is the name of the device node that you want to create,
type is either,
c for character ...