Using the HP-UX libIO Library

Device number (dev_t)
The operating system communicates with the hardware by associating the driver
name with a hardware address and recognizes interface and device drivers by a
unique number named dev_t. In HP-UX 11i v3, there are legacy dev_ts and agile
dev_ts. An agile dev_t is the dev_t of an agile I/O node; a legacy dev_t is the
dev_t of a legacy I/O node.
Device Special File (DSF)
A special file used to communicate with a device driver. Starting with HP-UX 11i v3,
there are two types of DSFs, legacy and persistent. See intro (7).
Block special file
A special file associated with a device that transfers data in multiple byte blocks,
rather than by series of individual bytes (see character special file), is called block
special file.
Character special file
A device special file associated with character driver that transfers data byte by
byte. Byte-mode I/O devices include terminals and disk drives accessed in “raw”
mode.
Persistent DSF
A DSF following the agile naming model conventions.
Legacy DSF
A device special file naming convention used prior to HP-UX 11i v3. This convention
is maintained in HP-UX 11i v3 for backward compatibility.
Major number
A number used exclusively to create special files that enable I/O to/from specific
devices. This number indicates the device driver to use for the device. Refer to the
man page mknod(2).
Minor number
A number that is an attribute of a DSF. Minor numbers are specified during their
creation and used to enable I/O to or from specific devices. This number is passed
to the device driver and is used to select the device from a family of devices. It is
also used to select some operational modes. The exact format and interpretation of
the minor number is both system and driver dependent.