Users Guide

176 Glossary
h
Abbreviation for hexadecimal. A base-16 numbering system, often used in
programming to identify addresses in the system's RAM and I/O memory
addresses for devices. The sequence of decimal numbers from 0 through 16, for
example, is expressed in hexadecimal notation as: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B,
C, D, E, F, 10. In text, hexadecimal numbers are often followed by h.
HBA
Abbreviation for host bus adapter. A PCI adapter card that resides in the system
whose only function is to convert data commands from PCI-bus format to storage
interconnect format (examples: SCSI, Fibre Channel) and communicate directly
with hard drives, tape drives, CD drives, or other storage devices.
heat sink
A metal plate with metal pegs or ribs that help dissipate heat. Most
microprocessors include a heat sink.
HMA
Abbreviation for high memory area. The first 64 KB of extended memory above
1 MB. A memory manager that conforms to the XMS can make the HMA a direct
extension of conventional memory. Also see XMM.
host adapter
A host adapter implements communication between the system's bus and the
controller for a peripheral device. (hard drive controller subsystems include
integrated host adapter circuitry.) To add a SCSI expansion bus to your system,
you must install or connect the appropriate host adapter.
hot plug
The ability to remove and replace a redundant part while the system is still
running. Also called a "hot spare."
HPFS
Abbreviation for the High Performance File System option in the Windows NT
operating systems.
HTTP
Abbreviation for Hypertext Transfer Protocol. HTTP is the client-server TCP/IP
protocol used on the World Wide Web for the exchange of HTML documents.