Specifications

D
evice Driver Programming
Glossary-2
block data transfer
The method of transferring data in units (blocks) between a block device such as a mag-
netic tape drive or disk drive and a user program.
block device
A device, such as a magnetic tape drive or disk drive, that conveys data in blocks through
the buffer management code. Compare character device.
block driver
A device driver, such as for a magnetic tape device or disk drive, that conveys data in
blocks through the buffer management code (for example, the buf structure). One driver
is written for each major number employed by block devices.
block I/O
A data transfer method used by drivers for block access devices. Block I/O uses the sys-
tem buffer cache as an intermediate data storage area between user memory and the
device.
block
The basic unit of data for I/O access. A block is measured in bytes. The size of a block
differs between computers, file system sizes, or devices.
boot device
The device that stores the self-configuration and system initialization code and necessary
file systems to start the operating system.
bootable object file
A file that is created and used to build a new version of the operating system.
bootstrap
The process of bringing up the operating system by its own action. The first few instruc-
tions load the rest of the operating system into the computer.
boot
The process of starting the operating system. The boot process consists of self-configura-
tion and system initialization.
buffer
A staging area for input-output (I/O) processes where arbitrary-length transactions are col-
lected into convenient units for system operations. A buffer consists of two parts: a mem-
ory array that contains data from the disk and a buffer header that identifies the buffer.