What is a “Computer Network” ?

April 15, 2014

Computer Network (Data Network) - is a telecommunications network that allows computers to exchange data. In computer networks, networked computing devices pass data to each other along data connections. The connections (network links) between nodes are established using either cable media or wireless media. The best-known computer network is the Internet.

Network computer devices that originate, route and terminate the data are called network nodes. Nodes can include hosts such as personal computers,phones, servers as well as networking hardware. Two such devices are said to be networked together when one device is able to exchange information with the other device, whether or not they have a direct connection to each other.

Computer networks support applications such as access to the World Wide Web, shared use of application and storage servers, printers, and fax machines, and use of email and instant messaging applications. Computer networks differ in the physical media used to transmit their signals, the communications protocols to organize network traffic, the network’s size, topology and organizational intent.

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Source: Wikipedia


What is “Ethernet” ?

April 8, 2014

Ethernet - is a family of computer networking technologies for local area networks (LANs). Ethernet was commercially introduced in 1980 and standardized in 1983 as IEEE 802.3. Ethernet has largely replaced competing wired LAN technologies such as token ring, FDDI, and ARCNET.

The Ethernet standards comprise several wiring and signaling variants of the OSI physical layer in use with Ethernet. The original 10BASE5 Ethernet used coaxial cable as a shared medium. Later the coaxial cables were replaced with twisted pair and fiber optic links in conjunction with hubs or switches. Data rates were periodically increased from the original 10 megabits per second to 100 gigabits per second.

Systems communicating over Ethernet divide a stream of data into shorter pieces called frames. Each frame contains source and destination addresses and error-checking data so that damaged data can be detected and re-transmitted. As per the OSI model Ethernet provides services up to and including the data link layer.

Since its commercial release, Ethernet has retained a good degree of compatibility. Features such as the 48-bit MAC address and Ethernet frame format have influenced other networking protocols.

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Source: Wikipedia


What Is “CD” ?

April 1, 2014

CD - (Sometimes explained as “compact disc”) is a digital optical disc data storage format. The format was originally developed to store and play back sound recordings only (CD-DA), but was later adapted for storage of data (CD-ROM). Several other formats were further derived from these, including write-once audio and data storage (CD-R), rewritable media (CD-RW), Video Compact Disc (VCD), Super Video Compact Disc (SVCD), Photo CD, PictureCD, CD-i, and Enhanced Music CD. Audio CDs and audio CD players have been commercially available since October 1982.

Standard CDs have a diameter of 120 millimetres (4.7 in) and can hold up to about 80 minutes of uncompressed audio or 700 MiB (actually about 703 MiB or 737 MB) of data. The Mini CD has various diameters ranging from 60 to 80 millimetres (2.4 to 3.1 in); they are sometimes used for CD singles, storing up to 24 minutes of audio or delivering device drivers.

At the time of the technology’s introduction it had much greater capacity than computer hard drives common at the time. The reverse is now true, with hard drives far exceeding the capacity of CDs.

In 2004, worldwide sales of CD audio, CD-ROM, and CD-R reached about 30 billion discs. By 2007, 200 billion CDs had been sold worldwide. Compact discs are increasingly being replaced or supplemented by other forms of digital distribution and storage, such as downloading and flash drives, with audio CD sales dropping nearly 50% from their peak in 2000.

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Source: Wikipedia


What Is “DVD” ?

March 25, 2014

DVD  – (Sometimes explained as “digital video disc” or “digital versatile disc”) is a digital optical disc storage format, invented and developed by Philips, Sony, Toshiba, and Panasonic in 1995. DVDs offer higher storage capacity than compact discs while having the same dimensions.

Pre-recorded DVDs are mass-produced using molding machines that physically stamp data onto the DVD. Such discs are known as DVD-ROM, because data can only be read and not written or erased. Blank recordable DVD discs (DVD-R and DVD+R) can be recorded once using a DVD recorder and then function as a DVD-ROM. Rewritable DVDs (DVD-RW, DVD+RW, and DVD-RAM) can be recorded and erased multiple times.

DVDs are used in DVD-Video consumer digital video format and in DVD-Audio consumer digital audio format, as well as for authoring DVD discs written in a special AVCHD format to hold high definition material (often in conjunction with AVCHD format camcorders). DVDs containing other types of information may be referred to as DVD data discs.

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Source: Wikipedia


What Is An “Archival Disc” ?

March 18, 2014

Archival Disc - is the name of a trademark owned by Sony Corporation and Panasonic Corporation describing an optical disc storage medium designed for long-term digital storage. First announced on 10 March 2014 and planned to be introduced in Q2 2015, the discs are intended to be able to withstand changes in temperature and humidity, in addition to dust and water, ensuring that the disc is readable for at least 50 years. The discs are intended to eventually be able to store up to one terabyte of data, based on the roadmap plans of both companies. The agreement between Sony and Panasonic to jointly develop the upcoming generation optical media standard was first announced on 29 July 2013.

The Archival Disc standard jointly developed by Sony and Panasonic will utilise signal processing technologies such as narrow track pitch crosstalk cancellation, high linear density inter-symbol interference cancellation and multi-level recording. The disc structure will feature dual sides, with three layers on each side, and a Land and Groove format. The track pitch is 0.225μm, the data bit length is 79.5nm, and the standard will utilise the method of Reed-Solomon Code error detection.

Sony expects the new standard to see usage in the film industry (such as storage of 4K resolution audiovisual data), archival services, and cloud data centres handling big data. The disc format is not intended as a consumer storage medium as of present, but are intended by the two companies as a solution for professional-level data archival. In order to reach a larger capacity whilst ensuring higher playback signal quality, the standard will employ crosstalk cancellation and Partial Response Maximum Likelihood (PRML) signal processing. Both companies will market the optical format under their respective brands.

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Source: Wikipedia


What Is “Blu ray” ?

March 11, 2014

Blu ray - or BD is a digital optical disc data storage format designed to supersede the DVD format, in that it is capable of storing high-definition video resolution (1080p). The plastic disc is 120 mm in diameter and 1.2 mm thick, the same size as DVDs and CDs.

Conventional (pre-BD-XL) Blu-ray Discs contain 25 GB per layer, with dual layer discs (50 GB) being the industry standard for feature-length video discs. Triple layer discs (100 GB) and quadruple layers (128 GB) are available for BD-XL re-writer drives. The name Blu-ray Disc refers to the blue laser used to read the disc, which allows information to be stored at a greater density than is possible with the longer-wavelength red laser used for DVDs. The major application of Blu-ray Discs is as a medium for video material such as feature films. Besides the hardware specifications, Blu-ray Disc is associated with a set of multimedia formats. Generally, these formats allow for the video and audio to be stored with greater definition than on DVD.

High-definition video may be stored on Blu-ray Discs with up to 1080p resolution (1920×1080 pixels), at up to 60 (59.94) fields per second. The older DVD discs had a maximum resolution of 480p (720×480 pixels).

The format was developed by the Blu-ray Disc Association, a group representing makers of consumer electronics, computer hardware, and motion pictures. Sony unveiled the first Blu-ray Disc prototypes in October 2000, and the first prototype player was released in April 2003 in Japan. Afterwards, it continued to be developed until its official release in June 2006. As of June 2008, more than 2,500 Blu-ray Disc titles were available in Australia and the United Kingdom, with 3,500 in the United States and Canada. In Japan, as of July 2010, more than 3,300 titles have been released.

During the high definition optical disc format war, Blu-ray Disc competed with the HD DVD format. Toshiba, the main company that supported HD DVD, conceded in February 2008, releasing its own Blu-ray Disc player in late 2009.

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Source: Wikipedia


What Is “Dailymotion” ?

March 4, 2014

Dailymotion is a French video-sharing website on which users can upload, share and view videos. Its headquarters are located in the 17th arrondissement of Paris.

Dailymotion allows users to browse and upload videos by searching tags, channels, or user-created groups. The search system also introduces results based on other users’ searches. The maximum size of a video file is 4 GB. The length of the video files is also limited to 60 minutes, except for motionmakers and Official Users.

Dailymotion began expanding its physical presence internationally in 2008, when the company opened its office in London. Since then, Dailymotion offices have been opened in New York City (2009), San Francisco (2011), and Tokyo (2013). As of November 2012, the site was the 31st most visited website in the world with over 116 million unique visitors accessing the site each month.

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Source: Wikipedia


What Does “Y2K” Stand For ?

February 25, 2014

Y2K or The Millennium bug - was a problem for both digital (computer-related) and non-digital documentation and data storage situations which resulted from the practice of abbreviating a four-digit year to two digits.

In 1997, The British Standards Institute (BSI) developed a standard, DISC PD2000-1, which defines “Year 2000 Conformity requirements” as four rules:

  1. No valid date will cause any interruption in operations.
  2. Calculation of durations between, or the sequence of, pairs of dates will be correct whether any dates are in different centuries.
  3. In all interfaces and in all storage, the century must be unambiguous, either specified, or calculable by algorithm
  4. Year 2000 must be recognized as a leap year

It identifies two problems that may exist in many computer programs.

Firstly, the practice of representing the year with two digits becomes problematic with logical error(s) arising upon “rollover” from x99 to x00. This has caused some date-related processing to operate incorrectly for dates and times on and after 1 January 2000, and on other critical dates which were billed “event horizons”. Without corrective action, long-working systems would break down when the “… 97, 98, 99, 00 …” ascending numbering assumption suddenly became invalid.

Secondly, some programmers had misunderstood the rule that determines whether years that are exactly divisible by 100 are leap years, and assumed the year 2000 would not be a leap year. Although most years divisible by 100 are not leap years, if they are divisible by 400 then they are. Thus the year 2000 was a leap year.

Companies and organizations worldwide checked, fixed, and upgraded their computer systems.

The number of computer failures that occurred when the clocks rolled over into 2000 in spite of remedial work is not known; amongst other reasons is the reticence of organisations to report problems. 

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Source: Wikipedia


What Is “YouTube” ?

February 18, 2014

YouTube - is a video-sharing website, created by three former PayPal employees in February 2005 and owned by Google since late 2006, on which users can upload, view and share videos. The company is based in San Bruno, California, and uses Adobe Flash Video and HTML5 technology to display a wide variety of user-generated video content, including video clips, TV clips, and music videos, and amateur content such as video blogging, short original videos, and educational videos.

Most of the content on YouTube has been uploaded by individuals, but media corporations including CBS, the BBC, Vevo, Hulu, and other organizations offer some of their material via YouTube, as part of the YouTube partnership program. Unregistered users can watch videos, and registered users can upload an unlimited number of videos. Videos considered to contain potentially offensive content are available only to registered users affirming themselves to be at least 18 years old. YouTube, LLC was bought by Google for US$1.65 billion in November 2006 and now operates as a Google subsidiary.

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Source: Wikipedia


What Does “Wireless” Mean ?

February 11, 2014

Wireless - is the transfer of information between two or more points that are not connected by an electrical conductor.

The most common wireless technologies use radio. With radio waves distances can be short, such as a few meters for television or as far as thousands or even millions of kilometers for deep-space radio communications. It encompasses various types of fixed, mobile, and portable applications, including two-way radios, cellular telephones, personal digital assistants (PDAs), and wireless networking. Other examples of applications of radio wireless technology include GPS units, garage door openers, wireless computer mice, keyboards and headsets, headphones, radio receivers, satellite television, broadcast television and cordless telephones.

Somewhat less common methods of achieving wireless communications includes the use of other electromagnetic wireless technologies, such as light, magnetic, or electric fields or the use of sound.

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Source: Wikipedia


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