<<< Back

 

HAL (Hardware abstraction layer) The low-level part of Windows NT, written specifically for each CPU technology, so that only the HAL must change when platform components change.

Handshaking A modem term that describes the initial exchange between modems. It's like "are you there?" with the response "I am here."

Hard disk A mass storage device that transfers data between the computer's memory and the disk storage media. Hard disks are nonremovable, rotating, rigid, magnetic storage disks. There are some types of hard disk with removable rigid media in the form of disk packs. See also disk

Hardware The physical components of a computer.

Hard disk removable drives High-capacity drives, such as Zip or Jaz drives, that have disks that can be removed like floppy disks.

Hard drive stand by time The amount of time before a hard drive will shut down to conserve energy.

Hard-disk loading The illegal practice of installing unauthorized software on computers for sale. Hard-disk loading can typically be identified by the absance of original disks in the original system's shipment.

Hardware The physical machinery that constitutes the computer system, such as the monitor, the keyboard, the system unit, and the printer.

Hardware cache A disk cache that is contained in RAM chips built right on the disk controller.

Hardware profiles Configuration information about memory, CPU, and OS, for a PC. A PC may have more than one profile. For example, a docking station PC may have two profiles, one with and one without the notebook PC docked.

Hardware tree A database build each time Windows 95 starts up that contains a list of installed components and the resources they use,

HCL (Hardware Compatibility List) The list of all computers and peripheral devices that have been tested and are officially supported by Windows NT. (for more visit WWW.microsoft.com/hwtest)

Head actuator In a disk drive, the mechanism that moves the read/write head radially across the surface of the platter of the disk drive.

Header Information sent ahead of data being transferred over a network to identify it ti receiving protocols. An IP header consists of things such as header and datagram length, flags, checksum, addresses, and so on.

Heap A memory block set aside for a program's data. If the heap files up, an "Out of memory" error may occur, even if there is plenty of regular RAM left, especially in 16-bit applications.

Heat sink A piece of metal, with cooling fins, that can be attached to or mounted on an integrated circuit (such as the CPU) to dissipate heat.

High-speed modem A modem operating at speeds from 9,600 to 19,200 bits per second.

High-capacity floppy drives Large storage devices such as the Iomega 3.5-inch Zip drive, which stores 100 MB of data.

High-level format Formatting performed by means of the DOS FORMAT program (for example, FORMAT C:/S formats drive C and writes systems files to the drive).A file system created after the format, on drive C (e.g. FAT,FAT32).

HIMEM.SYS A utility tat makes memory above 640K available.

Hive A physical segment of the NT registry that is stored in a disk file.

HMA (High memory area) The first 64K of extended memory. The method of storing part of DOS in the high memory area is called loading DOS high.

Holographic images A three-dimensional image (created by holography) that is made up of a light interference pattern preserved in a medium such as photographic film and which changes when the angle of view changes. Because making unofficial copies of holographic images is extremely difficult, they are often used to tag products, such as software packages, as original, making it difficult to distribute illegal copies.

Hop count The number of routers a packet must pass through in a network in order to reach its destination.

Host adapter The circuit board that controls a SCSI bus that supports as many as eight separate devices, one of which is a host adapter that controls communication with the PC.

Host drive Typically drive H on a compressed drive. See Compressed drive.

Host swapping A system feature, desirable in file servers, whereby a hard drive can be removed and exchanged without powering down a computer.

Host system In telecommunications, the system that you have called up and to which you are connected, such as a BBS (bulletin board system) or an on-line service such as CompuServe.

HSM (Hierarchical Storage Management) System of ranking and storing information across a variety of device types.

HTTP (Hypertext Transfer Protocol) The common transfer protocol used by Internet browsers on the World Wide Web.

Hub A network device or box that provides a central location to connect cables.

Huffman Coding For a given character distribution, by assigning short codes to frequently occurring characters and longer codes to infrequently occurring characters, Huffman's minimum redundancy encoding minimises the average number of bytes required to represent the characters in a text.

Hz (Hertz) Unit of measurement for frequency, calculated in terms of vibrations, or cycles, per second. For example, a Pentium CPU may have a speed of 233 MHz (megahertz). For 16-bit stereo sound, 44,100 Hz is used.