Multimedia Glossary: H

Hex

Hexadecimal system

The Hexadecimal system is a sixteen-base numbering system that uses 16 different symbols for its numbers: the numbers 0-9, and alphabet characters A-F. The smallest unit of information used in computers are bits. Bits combine into larger units called bytes. The architecture of PCs is such that 1 byte equal 8 bits. A 2 byte system thus equals 16 bits. This system is called hex (Latin word) because it is a base-16 system.

The representation of the hex system consists of a combination of the commonly known 10-base numbering system (from 0 - 9) and the first six letters of the Latin alphabet (a-f). The first row in the table below shows the commonly used 10-base system, the second row the 16-base system. The 10-base numbering ends at 15. The number zero ( 0 ) is at position number 1.

Decimal:	0	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15
Hexadecimal:	0	1	2	3	4	5	6	7	8	9	a	b	c	d	e	f

If you have a decimal number that you wish to convert to hexadecimal, divide the number by 16. For example 128/8=8, 128 (decimal) = 80 (hexadecimal).

Hexadecimal system for color

In the Hexadecimal system for color description, each colour consists of a combination of red, green and blue values, written in hex format.

NB: There are zeros in the table below (not O's = oh's). In markup languages, such as HTML, the hexdec number must be preceded with the hash (#).

			R zone		G zone		B zone
	"	#	F	F	F	F	F	F	"
Red	"	#	F	F	0	0	0	0	"
Green	"	#	0	0	F	F	0	0	"
Blue	"	#	0	0	0	0	F	F	"

In HTML values should be marked in quotation marks. In CSS values are not marked in quotation marks.

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Home Page

A Home Page is the first web page that is accessed when a domain name is requested. This page contains links to other pages at the site and is technically known as the hub document. Technically there is absolutely no difference at all between a Home Page, Portal, Hub Document, Front Page, Main Page, First Page, Default Page or whatever other term you may have come across. They are just marketing names to sell the same thing.

HSB / HSV

Hue-Saturation-Brightness/Value

The HSB color model is also known as the HSV color model -- brightness and value are synonyms,

The HSB color model is an additive 3-feature color mixing system, like RGB. The 3 aspects are:

• Hue - the feature that makes a particular color
• Saturation (or intensity; also called chroma) - how much of the same hue is present
• Brightness - this is achieved by adding white or black to the basic color hue. Adding white adds to brightness, while adding black makes it duller, thus having less brightness

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HTML

HyperText Markup Language

HTML is a subset of SGML and was conceptualized by Tim Berners-Lee in 1989. HTML 0.0 was released by him in 1990. The success of the World Wide Web is partially due to the simplicity of HTML, the markup language used for marking documents to be distributed through the Internet.

HTML files take the extension html, but as DOS-based computers could only take 3-character extensions, it is often written as htm.

HTML is a structural language that serves as a container for document objects. It is like a mammal skeleton. HTML itself cannot do anything -- for that you need a program. And HTML should not be used for the appearance of a document (for which you should rather use a style sheet). From a purist persepctive, the only thing that HTML does is to mark items and locations in a document with markers (called tags). User agents (such as browsers) interpret these markers and deliver the structure of the document in specified ways. For example, if an item is marked as a Paragraph (in HTML <p>), a visual user agent will display its content according to the conventions of paragraph display.

You may have read that HTML is a language used for presentation. That is not theoretically correct as HTML is a child of SGML which is a structural language, not a representational language. However, when the WWW exploded, browser makers such as Netscape confused structure with style and when the W3C was established it merely declared the most commonly form of HTML at that stage to be HTML 3.1 (the most widely used level of HTML). This was a mistake, realized by the W3C, and rectified with HTML 4, which distinguishes between structure and style.
HTML is an extremely powerful tool, as testified by the billions of web pages that are marked with it.

HTTP

HyperText Transfer Protocol

HTTP is based on 8-bit transmission and the RFC 822 character set. HTTP 0.9 was released in 1992, while HTTP 1.1 became a formal standard in 2001.

HTTP is the protocol used for transporting web documents over internet lines. Some of the kinds of files that are handled by this protocol are HTML files, graphic files, sound files, animation sequence files, script files.

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https

HyperText Transfer Protocol Secure

This protocol is the same as HTTP, except that it has security features built in, usually some kind of encryption scheme. Users need keys to start the secure level, otherwise files cannot be accessed.

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Hub document

This is the more technical name for Home Page.

Hue

Hue is the feature that makes a particular additive color, that is, the primary color without any black or white, or the color in its purist form.

Hue-Saturation-Brightness/Value

See HSB

Hyperlink

A synonym for "link". A hyperlink links a document to one another document, or a document fragment to another document fragment. A link on a document can be activated and the user is then taken to that linked document or fragment. In web pages links were originally underlined to indicate that there is a link. With style sheets a textual link can take on any design features. Images and other objects can also be used as links.
Hyperlinking is one of the technoloogies that contributed to the success of the WWW (World Wide Web).

HTML

See HTML

HyperText Transfer Protocol

See HTTP

HyperText Transfer Protocol Secure

See https

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