Technical Terms for the Day

404 Error

A 404 error is a common website error message that indicates a webpage cannot be found. It may be produced when a user clicks an outdated (or "broken")link or when a URL is typed incorrectly in a Web browser's address field. Some websites display custom 404 error pages, which may look similar to other pages on the site. Other websites simply display the Web server's default error message text, which typically begins with "Not Found." Regardless of the appearance, a 404 error means the server is up and running, but the webpage or path to the webpage is not valid.

So why call it a "404 error" instead of simply a "Missing Webpage Error?" The reason is that 404 is an error code produced by the Web server when it cannot find a webpage. This error code is recognized by search engines, which helps prevent search engine crawlers from indexing bad URLs. 404 errors can also be read by Web scripts and Website monitoring tools, which can help Webmasters locate and fix broken links.

Other common Web server codes are 200, which means a webpage has been found, and 301, which indicates a file has moved to a new location. Like 404 errors, these status messages are not seen directly by users, but they are used by search engines and website monitoring software.

802.11b

802.11b is a Wi-Fi standard developed by the IEEE for transmitting data over a wireless network. It operates on a 2.4 GHz band and allows for wireless data transfers up to 11 Mbps. A faster standard, called 802.11g, was introduced a few years after 802.11b and supports data transfer rates up to 54 Mbps. This can make a difference in the speed of data transfers within a local network, but since broadband Internet access is limited to around 5 Mbps, a 802.11b wireless connection will not be a bottleneck for Internet access. Most wireless networks are based on either 802.11b or 802.11g.

802.11g

802.11g is a Wi-Fi standard developed by the IEEE for transmitting data over a wireless network. It operates on a 2.4 GHz bandwidth and supports data transfer rates up to 54 Mbps. 802.11g is backward compatible with 802.11b hardware, but if there are any 802.11b-based computers on the network, the entire network will have to run at 11 Mbps (the max speed that 802.11b supports). However, you can configure your 802.11g wireless router to only accept 802.11g devices, which will ensure your network runs at its top speed.

Blu-ray

Blu-ray is an optical disc format such as CD and DVD. It was developed for recording and playing back high-definition (HD) video and for storing large amounts of data. While a CD can hold 700 MB of data and a basic DVD can hold 4.7 GB of data, a single Blu-ray disc can hold up to 25 GB of data. Even a double sided, dual layer DVD (which are not common) can only hold 17 GB of data. Dual-layer Blu-ray discs will be able to store 50 GB of data. That is equivalent to 4 hours of HDTV.

Blu-ray discs can hold more information than other optical media because of the blue lasers the drives use. The laser is actually blue-violet, but "Blu-ray" rolls off the tounge a little easier than "Blu-violet-ray." The blue-violet laser has a shorter wavelength than the red lasers used for CDs and DVDs (405nm compared to 650nm). This allows the laser to focus on a smaller area, which makes it possible to cram significantly more data on a disc the same size as a CD or DVD. Proponents of the Blu-ray format say they expect Blu-ray devices to replace VCRs (thank goodness) and DVD recorders as more people make the transition to HDTV.

File Format

A file format defines the structure and type of data stored in a file. The structure of a typical file may include a header, metadata, saved content, and an end-of-file (EOF) marker. The data stored in the file depends on the purpose of the file format. Some files, such as XML files, are used to store lists of items, while others, such as JPEG image files simply contain a block of data.

A file format also defines whether the data is stored in a plain text or binary format. Plain text files can be opened and viewed in a standard text editor. While text-based files are easy to create, they often use up more space than comparable binary files. They also lack security, since the contents can be easily viewed by dragging the file to a text editor. Binary file formats can be compressed and are well-suited for storing graphics, audio, and video data. If you attempt to view a binary file in a text editor, most of the data will appear garbled and unintelligible, but you may see some header text that identifies the file's contents.

Some file formats are proprietary, while others are universal, or open formats. Proprietary file formats can only be opened by one or more related programs. For example, a compressed StuffIt X (.SITX) archive can only be opened by StuffIt Deluxe or StuffIt Expander. If you try to open a StuffIt X archive with WinZip or another file decompression tool, the file will not be recognized. Conversely, open file formats are publicly available and are recognized by multiple programs. For example, StuffIt Deluxe can also save compressed archives in a standard zipped (.ZIP) format, which can be opened by nearly all decompression utilities.

When software developers create applications that save files, choosing an appropriate file format is important. For some programs, it might make sense to use an open format, which is compatible with other applications. In other cases, using a proprietary format may give the developer a competitive advantage, since the files created with the program can only be opened with the developer's software. However, most people prefer to have multiple software options, so many developers have moved away from proprietary file formats and now use open formats instead. For example, Microsoft Word, which used to save word processing documents in the proprietary .DOC format now saves documents in the open .DOCX format, which is supported by multiple applications.

NOTE: While the term "file format" technically refers to the structure and content of a file, the term is also used interchangeably with "file type," which defines a specific type of file, such as a rich text file or a Photoshop document.

(Source:www.techterms.com)