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H
half-duplex
A system capable of
transmitting information in only one direction at a time over a
communications channel.
handle
In the user interface, an
interface added to an object that facilitates moving, sizing, reshaping,
or other functions pertaining to an object. In programming, a pointer to a
pointer, that is, a token that lets a program access an identified
resource.
handle
count
In Task Manager, the
number of object handles in a process's object
table.
handshaking
A series of signals
acknowledging that communication can take place between computers or other
devices. A hardware handshake is an exchange of signals over specific
wires (other than the data wires), in which each device indicates its
readiness to send or receive data. A software handshake consists of
signals transmitted over the same wires used to transfer data, as in
modem-to-modem communications over telephone lines.
handwriting input
device
A tool, such as a digital
pen and tablet, used to enter text by writing instead of typing. Along
with writing tablets, you can use 3-D drawing or Computer Aided Drafting
(CAD) tablets, or a tablet-PC. You can also write by moving your mouse on
the mouse pad.
handwriting
recognition
The ability to interpret
handwritten text and convert it into computer-readable text. Handwriting
recognition programs allow you to enter text using a pen stylus or other
handwriting input device, rather than a keyboard.
hard disk
A device, also called
hard disk drive, that contains one or more inflexible platters coated with
material in which data can be recorded magnetically with read/write heads.
The hard disk exists in a sealed case that protects it and allows the head
to fly 10 millionths to 25 millionths of an inch above the surface of a
platter. Data can both be stored and accessed much more quickly than on a
floppy disk.
hardware
The physical components
of a computer system, including any peripheral equipment such as printers,
modems, and mouse devices.
hardware
compression
A feature available on
some tape devices that automatically compresses the data that is being
stored on the device. This is usually an option that is turned on or off
in a backup program.
hardware
configuration
Resource settings that
have been allocated for a specific device. Each device on your computer
has a hardware configuration, which may consist of IRQ lines, DMA, an I/O
port, or memory address settings.
hardware
decoder
A type of digital video
disc (DVD) decoder that allows a DVD drive to display movies on your
computer screen. A hardware decoder uses both software and hardware to
display movies.
hardware
profile
Data that describes the
configuration and characteristics of specific computer equipment. This
information can be used to configure computers for using peripheral
devices.
hardware
type
A classification for
similar devices. For example, Imaging Device is a hardware type for
digital cameras and scanners.
hash
A fixed-size result that
is obtained by applying a one-way mathematical function (sometimes called
a hash algorithm) to an arbitrary amount of data. If there is a change in
the input data, the hash changes. The hash can be used in many operations,
including authentication and digital signing. A hash is also called a
message digest.
hash
algorithm
An algorithm used to
produce a hash value of some piece of data, such as a message or session
key. A good hash algorithm has a quality where changes in the input data
can change every bit in the resulting hash value; for this reason, hashes
are useful in detecting any modification in a large data object, such as a
message. Furthermore, a good hash algorithm makes it computationally
infeasible to construct two independent inputs that have the same hash.
Typical hash algorithms include MD2, MD4, MD5, and SHA-1. Hash algorithm
is also called a hash function.
Hash-based Message Authentication
Mode (HMAC)
A mechanism for message
authentication using cryptographic hash functions. HMAC can be used with
any iterative cryptographic hash function (for example, MD5 and SHA-1) in
combination with a secret shared key. The cryptographic strength of HMAC
depends on the properties of the underlying hash
function.
hexadecimal
A base-16 number system
represented by the digits 0 through 9 and the uppercase or lowercase
letters A (equivalent to decimal 10) through F (equivalent to decimal
15).
hibernation
A state in which your
computer shuts down after saving everything in memory on your hard disk.
When you bring your computer out of hibernation, all programs and
documents that were open are restored to your
desktop.
High
Contrast
A display feature that
instructs programs to change the color scheme to a high-contrast scheme
and to increase legibility whenever possible.
histogram
A chart consisting of
horizontal or vertical bars, the widths or heights of which represent the
values of certain data.
hive
A section of the registry
that appears as a file on your hard disk. The registry subtree is divided
into hives (named for their resemblance to the cellular structure of a
beehive). A hive is a discrete body of keys, subkeys, and values that is
rooted at the top of the registry hierarchy. A hive is backed by a single
file and a .log file, which are in the systemroot\System32\Config
or the systemroot\Profiles\username folders.
By default, most hive
files (Default, SAM, Security, and System) are stored in the
systemroot\System32\Config folder. The systemroot\Profiles
folder contains the user profile for each user of the computer. Because a
hive is a file, it can be moved from one system to another. However, you
must use the Registry Editor to edit the file.
home
folder
A folder (usually on a
file server) that administrators can assign to individual users or groups.
Administrators use home folders to consolidate user files onto specific
file servers for easy backup. Home folders are used by some programs as
the default folder for the Open and Save As dialog boxes.
Home folders are sometimes referred to as home
directories.
host
A Windows computer that
runs a server program or service used by network or remote clients. For
Network Load Balancing, a cluster consists of multiple hosts connected
over a local area network (LAN).
host name
The DNS name of a device
on a network. These names are used to locate computers on the network. To
find another computer, its host name must either appear in the Hosts file
or be known by a DNS server. For most Windows computers, the host name and
the computer name are the same.
host
priority
For Network Load
Balancing, a host's precedence for handling default network traffic for
TCP and UDP ports. It is used if a host within the cluster goes offline,
and it determines which host within the cluster will assume responsibility
for the traffic previously handled by the offline
host.
Hosts file
A local text file in the same format as the 4.3
Berkeley Software
Distribution (BSD) UNIX /etc/hosts file. This file maps host names to IP
addresses, and it is stored in the \%Systemroot%\System32\Drivers\Etc
folder.
hot
docking
The process of attaching
a laptop computer to a docking station while the computer is running, and
automatically activating the docking station's video display and other
functions.
HTTP
hub
A common connection point
for devices in a network. Typically used to connect segments of a local
area network (LAN), a hub contains multiple ports. When data arrives at
one port, it is copied to the other ports so that all segments of the LAN
can see the data.
hubbed
mode
A mode in which the
ARP/MARS provides ATM addresses to requesting clients in the form of a
multicast server (MCS) list value. In this mode, the ARP/MARS acts as a
multicast server, providing active forwarding of all multicast and
broadcast traffic destined for IP addresses contained within the ranges
specified in the list.
hue
The position of a color
along the color spectrum. For example, green is between yellow and blue.
This attribute can be set using Display in Control
Panel.
hyperlink
Colored and underlined
text or a graphic that you click to go to a file, a location in a file, an
HTML page on the World Wide Web, or an HTML page on an intranet.
Hyperlinks can also go to newsgroups and to Gopher, Telnet, and FTP sites.
In Windows folders,
hyperlinks are text links that appear in the folder's left pane. You can
click these links to perform tasks, such as moving or copying a file, or
to go to other places on your computer, such as the My Documents folder or
Control Panel.
Hypertext Markup Language
(HTML)
A simple markup language
used to create hypertext documents that are portable from one platform to
another. HTML files are simple ASCII text files with codes embedded
(indicated by markup tags) to denote formatting and hypertext
links.
Hypertext Transfer Protocol
(HTTP)
The protocol used to transfer information on the World
Wide Web. An HTTP address (one kind of Uniform Resource Locator [URL])
takes the form: http://www.microsoft.com. |
