Dell PowerEdge 6400 User Manual
Page 19
h
Hexadecimal. A base-16 numbering system, often used in programming to identify addresses in the computer'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 or preceded by 0x. MS-DOS conventional memory
—the first 640 KB of
memory addresses
—is from 00000h to 9FFFFh; the MS-DOS upper memory area—memory addresses between 640 KB and 1 MB—is from
A0000h to FFFFFh.
heat sink
A metal plate with metal pegs or ribs that help dissipate heat. Some microprocessors include a heat sink.
HMA
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. See also
,
host adapter
A host adapter implements communication between the computer's bus and the controller for a peripheral. (Hard-disk drive controller subsystems
include integrated host adapter circuitry.) To add a SCSI expansion bus to your system, you must install the appropriate host adapter.
HPFS
High Performance File System option in the Windows NT operating system.
Hz
hertz
I
I/O
Input/output. The keyboard and a printer, for example, are I/O devices. In general, I/O activity can be differentiated from computational activity. For
example, when a program sends a document to the printer, it is engaging in I/O activity; when the program sorts a list of terms, it is engaging in
computational activity.
ID
identification
interlacing
A technique for increasing video resolution by only updating alternate horizontal lines on the screen. Because interlacing can result in noticeable
screen flicker, most users prefer noninterlaced video adapter resolutions.
internal microprocessor cache
An instruction and data cache built into the microprocessor. The Pentium microprocessor, for example, includes a 16-KB internal cache, which is
set up as an 8-KB read-only instruction cache and an 8-KB read/write data cache.
IP
Internet Protocol
IPX
Internetwork Packet eXchange
IRQ
Interrupt request. A signal that data is about to be sent to or received by a peripheral travels by an IRQ line to the microprocessor. Each peripheral
connection must be assigned an IRQ number. For example, the first serial port in your computer (COM1) is assigned to IRQ4 by default. Two
devices can share the same IRQ assignment, but you cannot operate both devices simultaneously.
ISA
Industry-Standard Architecture. A 16-bit expansion bus design. The expansion-card connectors in an ISA computer are also compatible with 8-bit
ISA expansion cards.
ITE
information technology equipment