Multimedia Glossary: G

Gateway

A device interfacing networks that use different protocols. It thus translates between the different protocols. When the definition of Gateway is strict, it translates only between different high-level architectures, such as, say, between TCP/IP and IBM's SNA. When the definition is more loose, it translates between lower-level network types, say between Ethernet and Token Ring.

In a manner of speaking the function of a router and gateway is similar: they both act as interfacing translators in a network. Gateways are more general than routers as they translate between most (if not all) protocol layers of the OSI model. Also see bridge.

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GIF

Graphic Interchange Format

GIF is a bitmap method of compressing images, originally developed for quicker transport of images on The Internet, as file sizes of other graphic formats were too large. GIF87 is the basic compression scheme, while the later GIF89a supports transparency and animation.

Layering: GIF images that have more than 256 colors can be layered in order to display the image properly. Your graphics program must have the ability to save the file as such. Not all browsers support this feature. GIF uses the LZW (Lempel-Ziv-Welch) lossless compression scheme and supports 8-bit color (ie 256 colors).

GIFs are typically used for relatively simple images, such as company logos, stick figures, simple buttons, line images and so on. These images also have relatively few color hues. For more complex images, rather use JPEGs.

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gopher

Gopher is an internet service -- its method similar to ftp. Before more advanced and user-friendly FTP programs gopher was often used instead of FTP as it provided a graphical directory structure. File descriptions are also found on gopher sites, and links are often made to other similar sites. It is thus more useful than FTP.

Older internet users may remember using the gopher service Veronica that consists of a database of menu items that structures the information.

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Graphics

Graphics is a generic term for image-based signs and symbols. Technically text in a document is also a graphic symbol, but popularly text refers to human language characters, while graphics refer to pictures, icons and similar images.
The following terms are important for graphic images. Not all the graphic image compression techniques (GIF, JPEG, PNG) support each of these methods.

• Dithering - the process by which a large number of colors are forced into a smaller color palette
• Transparency - some parts of the color palette can be set as being transparent
• Anti-aliasing - the technique used for the smooth transition of colors into one another to avoid jagged edges
• Interlacing - the method used to load an image in small parts

Graphic Interchange Format

See GIF

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