I/O Systems

• One of the purposes of an OS is to hide the peculiarities of specific hardware devices from the user. For example, in UNIX, the peculiarities of I/O devices (including keyboards, monitors, printers, and so on) are hidden from the bulk of the OS itself by the I/O subsystem. The I/O subsystem consists of several components:
  • A memory-management component that includes buffering, caching, and spooling,
  • A general device-driver interface, that is, applies to many or all I/O devices equally well.
  • Drivers for specific hardware devices.
• Only the device driver knows the peculiarities of the specific device to which it is assigned.