Halftone
A simulation of continuous tones by the use of black or overlapping process color dots of varying size or position.

Halftoning Factor
See quality factor.

Halo
A light line around object edges in an image, produced by the USM (sharpening) technique.

Handle
Unique character string identifier assigned to each entry in the NIC WHOIS database.

Handshaking
The process computers and modems go through in order to establish a connection and agree on the speed and protocols for data transmission.

Hayes Compatible
A modem is considered Hayes Compatible if it supports the Hayes command set (a language used to communicate with and control a modem).

Header
The portion of a packet, preceding the actual data, containing source and destination addresses, error checking and other fields. A header is also the part of an electronic mail message that precedes the body of a message and contains, among other things, the message originator, date and time.

High Key
A light image that is intentionally lacking in shadow detail.

Highlight
The lightest tones in an image. A spectral highlight is a bright, reflected light source.

Histogram
A chart displaying the tonal ranges present in an image as a series of vertical bars.

Home Page
The document that is displayed when you first open a web client program. Also, commonly used to refer to the first document you come to in a collection of documents on a Web site.

Host
The main computer system to which users are connected.

Hostname
Name which officially identifies each computer attached to the Internet.

Hotlist
A file containing lists of Internet Web pages, enabling you to easily access your favorite Web pages.

HP
Hewlett Packard.

HTML
HyperText Markup Language. A system for tagging various parts of a Web document that tells the Web client programs how to display the document's text, links, graphics and attached media.

Hue
The color of an object perceived by the eye due to the fact that a single or pair of RGB primary colors predominates.

Hypermedia
Describes hypertext in which various types of data can be stored - sound, images, video and so on - as regular text.

Hypertext
A text-linking strategy that lets you jump between related information in a document by clicking on a button or highlighted word. On-line help systems often use hypertext links, as do some programs designed for the electronic distribution of documents.