An innovative feature is the treatment of devices—UNIX is designed to provide device
independence to the applications running under it. This is achieved by treating each
I/O device as a special type of file. Every device that’s installed in a UNIX system is
assigned a name that’s similar to the name given to any other file, which is given
descriptors called iodes. These descriptors identify the devices, contain information
about them, and are stored in the device directory. The subroutines that work with the
operating system to supervise the transmission of data between main memory and a
peripheral unit are called the device drivers.