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.
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.
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