A device file is an interface to a device driver. A device file is sometimes called a special file or a device special file. The device file allows a program to interact with the device using standard input/output system calls.

Two types of device file: * character - serial stream of characters * block - fixed size blocks, random access, buffered, example: disk

Most device files are managed as part of a virtual file system mounted at /dev.

Device file is pointer, not container.

size device numbers, major and minor major driver minor instance

full null random urandom zero

ls -li /dev | grep cdrom

ls -li /dev | grep tty

pts pseudo terminal slave a type of tty

/dev/pts character special file

xterm

bus

      PCI, ISA, EISA

cpu clock, 200 MHz pulses, per second system clock, time of day time-sharing clock, interrupt cpu as reminder to switch users

chipset

      NorthBridge
      SouthBridge