(short for co
oder) is a piece of software that converts a stream of digital information into audio or video that can be played back in an audio or video player.
For example, playing an H.264 file on your computer requires that you have the H.264 codec installed. Likewise with .ogg files — you need to have the Ogg codec installed in order for your computer to recognize the file format, decode it, and play it back.
Codecs have grown in importance on the web along with the proliferation of rich media websites. Browsers can only play songs and videos that are in formats it has codecs installed to handle. For this reason, most websites off-load media playback to plug-ins, which usually come with the ability to play popular filetypes. The Flash player is one such plugin.
Pretty Good Privacy is a flavor of algorithmic encryption that uses two cipher keys, one public and one private. Anyone can use a public key to send a scrambled message to the receiving party. The private key is then used only by the receiving party to unscramble incoming messages. The two-key system was developed by RSA Data Security, Inc. and PGP is the most popular type of two-key encryption available for public, non-commercial use.
To render a graphic means to draw a real-world object as it actually appears. There are two widely used rendering processes:ray tracing and scanline rendering. Scanline rendering creates images one vertical line at a time, while ray tracing renders object-by-object. In general, ray tracing produces better results, but scanline rendering is useful in animation, where the image quality of each individual frame isn’t as important as the finished product.
Server-side includes (SSI) tell a server to include information in a document before sending it to the browser. All directives to the server are formatted as SGML comments within the document. In case the document should find its way to the client unparsed
, it will harmlessly remain unrendered. Each server-side include is written in the format
!--#command tag1="value1" tag2="value2" --
. The simplest kind of SSI is a virtual include, which can use one command to pull HTML fragments, such as navigation bars, into all the pages of a site without having to hand code each page.
(see eXtended Server-Side Includes)
WAP, which stands for the wireless application protocol, is a standardized, device-independent protocol that defines the development and operating environment for wireless telephones, pagers and handheld devices. WAP utilizes a lighter version of the TCP/IP protocol for transmission between devices.