1.
Dell PowerEdge
–
The Dell PowerEdge line is Dells server computer product line. Most PowerEdge servers use the x86 architecture, the partnership between Intel and Dell remained close, with Intel remaining the exclusive source of processors in Dells servers until 2006. In May 2006 Dell announced that it intended to develop servers using AMD Opteron processors. The first Opteron-based PowerEdge systems, the PowerEdge 6950 and the PowerEdge SC1435, appeared in October 2006 PowerEdge machines come configured as tower, rack-mounted, Dell uses a consistent chip-set across servers in the same generation regardless of packaging, allowing for a common set of drivers and system-images. Original equipment manufacturers and value-added resellers also offer solutions based on PowerEdge servers, loaded with custom software and with minor cosmetic changes, Dells servers form the underlying hardware in certain appliances from IronPort, Google, Exinda Networks, and Enterasys. In 2007 the PowerEdge line accounted for approximately 15% of Dells overall revenue from computer-hardware sales and these cards were equipped with hardware from LSI Corporation or Intel,256 MBytes of memory, support up to 8x SATA3.0 Gbit/s drives without the use of expanders. They had an optional Battery Backup Unit to allow flexible use of the memory during writes, enhancing performance in RAID5 and 6. Although PowerEdge is mainly used to refer to there are a few systems where the term PowerEdge refers to systems of which servers are a part. The individual non-server components have also their own name in their own such as PowerConnect M-switches or EqualLogic blade-SAN. PowerEdge VRTX - the converged system consisting of 4 PowerEdge M-blade servers, the built-in storage solution and the I/O networking module. Since the introduction of the generation 10 servers in 2007 Dell adopted a method for naming their servers. The letter indicates the type of server, R indicates a 19 rack-mountable server, M indicates a blade server, while T indicates a stand-alone server. This letter is followed by 3 digits, The first digit refers to the number of CPU sockets in the system,1 to 3 for one socket,4 to 7 for two sockets, and 9 for four sockets. 8 can be two or four sockets depending on generation and CPU maker The middle digit refers to the generation,0 for Generation 10,1 for Generation 11. The third digit indicates the maker of the CPU,0 for Intel or 5 for Advanced Micro Devices, for example, The Dell PowerEdge M610 was a two-socket server of the 11th generation using an Intel CPU while the R605 was a two-socket AMD-based rack-server of the 10th generation. For example, the PowerEdge 2800 was the equivalent of the 2850. The naming applies to the tower version too, but the version will usually be between 5U and 6U. List of Dell PowerEdge Servers Dell Server Documentation Using a PowerEdge tower on its side in a rack Review Dell PowerEdge R810 Review Dell PowerEdge R815
Dell PowerEdge
–
Rack-mounted 11th generation PowerEdge servers
Dell PowerEdge
–
Rack-mountable 11th generation (11G) PowerEdge R610 server with the case opened and the front bezel removed
2.
Rack mount
–
A 19-inch rack is a standardized frame or enclosure for mounting multiple electronic equipment modules. Each module has a front panel that is 19 inches wide, the 19-inch dimension includes the edges, or ears, that protrude on each side which allow the module to be fastened to the rack frame with screws. Common uses include server, audio, and scientific lab equipment, the height of the electronic modules is also standardized as multiples of 1.752 inches or one rack unit or U. The industry standard rack cabinet is 42U tall, the term relay rack appeared first in the world of telephony. By 1911, the term was also being used in railroad signaling, there is little evidence that the dimensions of these early racks were standardized. The 19-inch rack format with rack-units of 1.75 inches was established as a standard by AT&T around 1922 in order to reduce the space required for repeater, the earliest repeaters from 1914 were installed in ad-hoc fashion on shelves, in wooden boxes and cabinets. Once serial production started, they were built into bespoke racks, the height of the different panels will vary, but in all cases to be a whole multiple of 1¾ inches. The 19-inch rack format has remained constant while the technology that is mounted within it has changed considerably, nineteen-inch racks in two-post or four-post form hold most equipment in modern data centers, ISP facilities, and professionally designed corporate server rooms. They allow for dense hardware configurations without occupying excessive floorspace or requiring shelving, nineteen-inch racks are also often used to house professional audio and video equipment, including amplifiers, effects units, interfaces, headphone amplifiers, and even small scale audio mixers. A third common use for rack-mounted equipment is industrial power, control, typically, a piece of equipment being installed has a front panel height 1⁄32 inch less than the allotted number of Us. Thus, a 1U rackmount computer is not 1.75 inches tall but is 1.719 inches tall, 2U would be 3.469 inches instead of 3.5 inches. This gap allows a bit of room above and below a piece of equipment so it may be removed without binding on the adjacent equipment. State-of-the-art rackmount cases are now constructed of thermo stamped composite, carbon fiber. Originally, the holes were tapped with a particular screw thread. Tapping large numbers of holes that may never be used is expensive, nonetheless tapped-hole racks are still in use, examples include telephone exchanges, network cabling panels, broadcast studios and some government and military applications. The tapped-hole rack was first replaced by clearance-hole racks, the holes are large enough to permit a bolt to be freely inserted through without binding, and bolts are fastened in place using cage nuts. In the event of a nut being stripped out or a bolt breaking, production of clearance-hole racks is less expensive because tapping the holes is eliminated and replaced with fewer, less expensive, cage nuts. The next innovation in design has been the square-hole rack
Rack mount
–
Numerous 19-inch racks in a professional audio application
Rack mount
–
19-inch rack
Rack mount
–
A 19-inch rack used for
switches at the
DE-CIX in
Frankfurt,
Germany
Rack mount
–
3U rackmount system
3.
HTTP
–
The Hypertext Transfer Protocol is an application protocol for distributed, collaborative, and hypermedia information systems. HTTP is the foundation of data communication for the World Wide Web, Hypertext is structured text that uses logical links between nodes containing text. HTTP is the protocol to exchange or transfer hypertext, development of HTTP was initiated by Tim Berners-Lee at CERN in 1989. Standards development of HTTP was coordinated by the Internet Engineering Task Force and the World Wide Web Consortium, culminating in the publication of a series of Requests for Comments. The first definition of HTTP/1.1, the version of HTTP in common use, occurred in RFC2068 in 1997, although this was obsoleted by RFC2616 in 1999 and then again by RFC7230 and family in 2014. A later version, the successor HTTP/2, was standardized in 2015, HTTP functions as a request–response protocol in the client–server computing model. A web browser, for example, may be the client, the client submits an HTTP request message to the server. The server, which provides resources such as HTML files and other content, or performs other functions on behalf of the client, the response contains completion status information about the request and may also contain requested content in its message body. A web browser is an example of a user agent, other types of user agent include the indexing software used by search providers, voice browsers, mobile apps, and other software that accesses, consumes, or displays web content. HTTP is designed to permit intermediate network elements to improve or enable communications between clients and servers, high-traffic websites often benefit from web cache servers that deliver content on behalf of upstream servers to improve response time. Web browsers cache previously accessed web resources and reuse them when possible to network traffic. HTTP proxy servers at private network boundaries can facilitate communication for clients without a globally routable address, HTTP is an application layer protocol designed within the framework of the Internet protocol suite. Its definition presumes an underlying and reliable transport layer protocol, however HTTP can be adapted to use unreliable protocols such as the User Datagram Protocol, for example in HTTPU and Simple Service Discovery Protocol. HTTP resources are identified and located on the network by Uniform Resource Locators, using the Uniform Resource Identifiers schemes http, uRIs and hyperlinks in HTML documents form inter-linked hypertext documents. HTTP/1.1 is a revision of the original HTTP, in HTTP/1.0 a separate connection to the same server is made for every resource request. HTTP/1.1 can reuse a connection multiple times to download images, scripts, stylesheets, HTTP/1.1 communications therefore experience less latency as the establishment of TCP connections presents considerable overhead. Tim Berners-Lee and his team at CERN are credited with inventing the original HTTP along with HTML and the technology for a web server. Berners-Lee first proposed the WorldWideWeb project in 1989—now known as the World Wide Web, the first version of the protocol had only one method, namely GET, which would request a page from a server
HTTP
–
URL beginning with the HTTP scheme and the
WWW domain name label.
HTTP
–
Tim Berners-Lee
4.
Network protocol
–
These are the rules or standard that defines the syntax, semantics and synchronization of communication and possible error recovery methods. Protocols may be implemented by hardware, software, or a combination of both, Communicating systems use well-defined formats for exchanging various messages. Each message has a meaning intended to elicit a response from a range of possible responses pre-determined for that particular situation. The specified behavior is independent of how it is to be implemented. Communications protocols have to be agreed upon by the parties involved, to reach agreement, a protocol may be developed into a technical standard. Multiple protocols often describe different aspects of a single communication, a group of protocols designed to work together are known as a protocol suite, when implemented in software they are a protocol stack. Most recent protocols are assigned by the IETF for Internet communication, the ITU-T handles telecommunications protocols and formats for the PSTN. As the PSTN and Internet converge, the two sets of standards are also being driven towards convergence, the nature of a communication, the actual data exchanged and any state-dependent behaviors, is defined by these specifications. In digital computing systems, the rules can be expressed by algorithms, expressing the algorithms in a portable programming language makes the protocol software operating-system independent. Operating systems usually contain a set of cooperating processes that manipulate shared data to communicate each other. This communication is governed by protocols, which can be embedded in the process code itself. In contrast, because there is no memory, communicating systems have to communicate with each other using a shared transmission medium. Transmission is not necessarily reliable, and individual systems may use different hardware or operating systems, to implement a networking protocol, the protocol software modules are interfaced with a framework implemented on the machines operating system. This framework implements the functionality of the operating system. The best known frameworks are the TCP/IP model and the OSI model and this gave rise to the concept of layered protocols which nowadays forms the basis of protocol design. Systems typically do not use a protocol to handle a transmission. Instead they use a set of cooperating protocols, sometimes called a family or protocol suite. Some of the best known protocol suites are TCP/IP, IPX/SPX, X.25, AX.25, the protocols can be arranged based on functionality in groups, for instance there is a group of transport protocols
Network protocol
–
Figure 2. The TCP/IP model or Internet layering scheme and its relation to some common protocols.
5.
World Wide Web
–
The World Wide Web is an information space where documents and other web resources are identified by Uniform Resource Locators, interlinked by hypertext links, and can be accessed via the Internet. English scientist Tim Berners-Lee invented the World Wide Web in 1989 and he wrote the first web browser computer program in 1990 while employed at CERN in Switzerland. The Web browser was released outside of CERN in 1991, first to research institutions starting in January 1991. The World Wide Web has been central to the development of the Information Age and is the primary tool billions of people use to interact on the Internet, Web pages are primarily text documents formatted and annotated with Hypertext Markup Language. In addition to formatted text, web pages may contain images, video, audio, embedded hyperlinks permit users to navigate between web pages. Multiple web pages with a theme, a common domain name. Website content can largely be provided by the publisher, or interactive where users contribute content or the content depends upon the user or their actions, websites may be mostly informative, primarily for entertainment, or largely for commercial, governmental, or non-governmental organisational purposes. In the 2006 Great British Design Quest organised by the BBC and the Design Museum, Tim Berners-Lees vision of a global hyperlinked information system became a possibility by the second half of the 1980s. By 1985, the global Internet began to proliferate in Europe, in 1988 the first direct IP connection between Europe and North America was made and Berners-Lee began to openly discuss the possibility of a web-like system at CERN. Such a system, he explained, could be referred to using one of the meanings of the word hypertext. At this point HTML and HTTP had already been in development for two months and the first Web server was about a month from completing its first successful test. While the read-only goal was met, accessible authorship of web content took longer to mature, with the concept, WebDAV, blogs, Web 2.0. The proposal was modelled after the SGML reader Dynatext by Electronic Book Technology, a NeXT Computer was used by Berners-Lee as the worlds first web server and also to write the first web browser, WorldWideWeb, in 1990. By Christmas 1990, Berners-Lee had built all the necessary for a working Web, the first web browser. The first web site, which described the project itself, was published on 20 December 1990, jones stored it on a magneto-optical drive and on his NeXT computer. On 6 August 1991, Berners-Lee published a summary of the World Wide Web project on the newsgroup alt. hypertext. This date is confused with the public availability of the first web servers. The first server outside Europe was installed at the Stanford Linear Accelerator Center in Palo Alto, California, accounts differ substantially as to the date of this event
World Wide Web
–
The NeXT Computer used by
Tim Berners-Lee at
CERN.
World Wide Web
–
The CERN
data center in 2010 housing some WWW servers
6.
Software
–
Computer software, or simply software, is that part of a computer system that consists of data or computer instructions, in contrast to the physical hardware from which the system is built. In computer science and software engineering, computer software is all information processed by computer systems, programs, computer software includes computer programs, libraries and related non-executable data, such as online documentation or digital media. Computer hardware and software require each other and neither can be used on its own. At the lowest level, executable code consists of machine language instructions specific to an individual processor—typically a central processing unit, a machine language consists of groups of binary values signifying processor instructions that change the state of the computer from its preceding state. For example, an instruction may change the value stored in a storage location in the computer—an effect that is not directly observable to the user. An instruction may also cause something to appear on a display of the computer system—a state change which should be visible to the user. The processor carries out the instructions in the order they are provided, unless it is instructed to jump to a different instruction, the majority of software is written in high-level programming languages that are easier and more efficient for programmers, meaning closer to a natural language. High-level languages are translated into machine language using a compiler or an interpreter or a combination of the two, an outline for what would have been the first piece of software was written by Ada Lovelace in the 19th century, for the planned Analytical Engine. However, neither the Analytical Engine nor any software for it were ever created, the first theory about software—prior to creation of computers as we know them today—was proposed by Alan Turing in his 1935 essay Computable numbers with an application to the Entscheidungsproblem. This eventually led to the creation of the academic fields of computer science and software engineering. Computer science is more theoretical, whereas software engineering focuses on practical concerns. However, prior to 1946, software as we now understand it—programs stored in the memory of stored-program digital computers—did not yet exist, the first electronic computing devices were instead rewired in order to reprogram them. On virtually all platforms, software can be grouped into a few broad categories. There are many different types of software, because the range of tasks that can be performed with a modern computer is so large—see list of software. System software includes, Operating systems, which are collections of software that manage resources and provides common services for other software that runs on top of them. Supervisory programs, boot loaders, shells and window systems are parts of operating systems. In practice, an operating system bundled with additional software so that a user can potentially do some work with a computer that only has an operating system. Device drivers, which operate or control a particular type of device that is attached to a computer, utilities, which are computer programs designed to assist users in the maintenance and care of their computers
Software
7.
Web page
–
A web page is a document that is suitable for the World Wide Web and web browsers. A web browser displays a web page on a monitor or mobile device, the web page is what displays, but the term also refers to a computer file, usually written in HTML or comparable markup language. Web browsers coordinate the various web resource elements for the web page, such as style sheets, scripts. Typical web pages provide hypertext that includes a bar or a sidebar menu to other web pages via hyperlinks. On a network, a web browser can retrieve a web page from a web server. On a higher level, the web server may restrict access to only a network such as a corporate intranet or it provides access to the World Wide Web. On a lower level, the web browser uses the Hypertext Transfer Protocol to make such requests, dynamic website pages help the browser to enhance the web page through user input to the server. Web pages usually include information as to the colors of text and backgrounds, an HTTP1.1 web server will maintain a connection with the browser until all related resources have been requested and provided. Web browsers usually render images along with the text and other material on the web page. These scripts may run on the client computer, if the user allows, a web browser can have a Graphical User Interface, like Internet Explorer, Mozilla Firefox, Google Chrome, and Opera, or can be text-based, like Lynx or Links. Web users with disabilities often use assistive technologies and adaptive strategies to access web pages, disabled and able-bodied users may disable the download and viewing of images and other media, to save time, network bandwidth or merely to simplify their browsing experience. Users of mobile devices often have restricted displays and bandwidth, anyone may prefer not to use the fonts, font sizes, styles and color schemes selected by the web page designer and may apply their own CSS styling to the page. The World Wide Web Consortium and Web Accessibility Initiative recommend that all web pages should be designed with all of options in mind. Non-textual information, Static images may be raster graphics, typically GIF, JPEG or PNG, Animated images typically Animated GIF and SVG, but also may be Flash, Shockwave, or Java applet. Audio, typically MP3, Ogg or various proprietary formats, video, WMV, RM, FLV, MPG, MOV Interactive information, see interactive media. For on page interaction, Interactive text, see DHTML, Interactive illustrations, ranging from click to play images to games, typically using script orchestration, Flash, Java applets, SVG, or Shockwave. Buttons, forms providing an interface, typically for use with script orchestration. For between pages interaction, Hyperlinks, standard change page reactivity, forms, providing more interaction with the server and server-side databases
Web page
–
A
screenshot of
Wikimedia Commons, a web page
8.
Client (computing)
–
A client is a piece of computer hardware or software that accesses a service made available by a server. The server is often on another system, in which case the client accesses the service by way of a network. The term applies to the role that programs or devices play in the client–server model, a client is a computer program that, as part of its operation, relies on sending a request to another computer program. For example, web browsers are clients that connect to web servers, email clients retrieve email from mail servers. Online chat uses a variety of clients, which depending on the chat protocol being used. Multiplayer video games or online video games may run as a client on each computer, the term client may also be applied to computers or devices that run the client software or users that use the client software. A client is part of a model, which is still used today. Clients and servers may be computer programs run on the same machine, combined with Internet sockets, programs may connect to a service operating on a possibly remote system through the Internet protocol suite. Servers wait for clients to initiate connections that they may accept. The term was first applied to devices that were not capable of running their own stand-alone programs and these dumb terminals were clients of the time-sharing mainframe computer. In one classification, client computers and devices are either fat clients, thin clients, or hybrid clients. A fat client, also known as a client or thick client, is a client that performs the bulk of any data processing operations itself. The personal computer is an example of a fat client, because of its relatively large set of features and capabilities. For example, a running a CAD program that ultimately shares the result of its work on a network is a fat client. A thin client is a sort of client. Thin clients use the resources of the host computer, a thin client generally only presents processed data provided by an application server, which performs the bulk of any required data processing. A device using web application is a thin client, a hybrid client is a mixture of the above two client models. Similar to a fat client, it processes locally, but relies on the server for storing persistent data and this approach offers features from both the fat client and the thin client
Client (computing)
–
A thin client
Client (computing)
–
A
computer network diagram of client computers communicating with a server computer via the
Internet
9.
Hypertext Transfer Protocol
–
The Hypertext Transfer Protocol is an application protocol for distributed, collaborative, and hypermedia information systems. HTTP is the foundation of data communication for the World Wide Web, Hypertext is structured text that uses logical links between nodes containing text. HTTP is the protocol to exchange or transfer hypertext, development of HTTP was initiated by Tim Berners-Lee at CERN in 1989. Standards development of HTTP was coordinated by the Internet Engineering Task Force and the World Wide Web Consortium, culminating in the publication of a series of Requests for Comments. The first definition of HTTP/1.1, the version of HTTP in common use, occurred in RFC2068 in 1997, although this was obsoleted by RFC2616 in 1999 and then again by RFC7230 and family in 2014. A later version, the successor HTTP/2, was standardized in 2015, HTTP functions as a request–response protocol in the client–server computing model. A web browser, for example, may be the client, the client submits an HTTP request message to the server. The server, which provides resources such as HTML files and other content, or performs other functions on behalf of the client, the response contains completion status information about the request and may also contain requested content in its message body. A web browser is an example of a user agent, other types of user agent include the indexing software used by search providers, voice browsers, mobile apps, and other software that accesses, consumes, or displays web content. HTTP is designed to permit intermediate network elements to improve or enable communications between clients and servers, high-traffic websites often benefit from web cache servers that deliver content on behalf of upstream servers to improve response time. Web browsers cache previously accessed web resources and reuse them when possible to network traffic. HTTP proxy servers at private network boundaries can facilitate communication for clients without a globally routable address, HTTP is an application layer protocol designed within the framework of the Internet protocol suite. Its definition presumes an underlying and reliable transport layer protocol, however HTTP can be adapted to use unreliable protocols such as the User Datagram Protocol, for example in HTTPU and Simple Service Discovery Protocol. HTTP resources are identified and located on the network by Uniform Resource Locators, using the Uniform Resource Identifiers schemes http, uRIs and hyperlinks in HTML documents form inter-linked hypertext documents. HTTP/1.1 is a revision of the original HTTP, in HTTP/1.0 a separate connection to the same server is made for every resource request. HTTP/1.1 can reuse a connection multiple times to download images, scripts, stylesheets, HTTP/1.1 communications therefore experience less latency as the establishment of TCP connections presents considerable overhead. Tim Berners-Lee and his team at CERN are credited with inventing the original HTTP along with HTML and the technology for a web server. Berners-Lee first proposed the WorldWideWeb project in 1989—now known as the World Wide Web, the first version of the protocol had only one method, namely GET, which would request a page from a server
Hypertext Transfer Protocol
–
URL beginning with the HTTP scheme and the
WWW domain name label.
Hypertext Transfer Protocol
–
Tim Berners-Lee
10.
HTML
–
Hypertext Markup Language is the standard markup language for creating web pages and web applications. With Cascading Style Sheets and JavaScript it forms a triad of cornerstone technologies for the World Wide Web, Web browsers receive HTML documents from a webserver or from local storage and render them into multimedia web pages. HTML describes the structure of a web page semantically and originally included cues for the appearance of the document, HTML elements are the building blocks of HTML pages. With HTML constructs, images and other objects, such as interactive forms and it provides a means to create structured documents by denoting structural semantics for text such as headings, paragraphs, lists, links, quotes and other items. HTML elements are delineated by tags, written using angle brackets, tags such as <img /> and <input /> introduce content into the page directly. Include explicit close tags for elements that permit content but are left empty, by carefully following the W3Cs compatibility guidelines, a user agent should be able to interpret the document equally as HTML or XHTML. For documents that are XHTML1.0 and have made compatible in this way. When delivered as XHTML, browsers should use an XML parser, HTML4 defined three different versions of the language, Strict, Transitional and Frameset. The Transitional and Frameset versions allow for presentational markup, which is omitted in the Strict version, instead, cascading style sheets are encouraged to improve the presentation of HTML documents. Because XHTML1 only defines an XML syntax for the language defined by HTML4, as this list demonstrates, the loose versions of the specification are maintained for legacy support. However, contrary to popular misconceptions, the move to XHTML does not imply a removal of this legacy support, rather the X in XML stands for extensible and the W3C is modularizing the entire specification and opening it up to independent extensions. The primary achievement in the move from XHTML1.0 to XHTML1.1 is the modularization of the entire specification, the strict version of HTML is deployed in XHTML1.1 through a set of modular extensions to the base XHTML1.1 specification. Likewise, someone looking for the loose or frameset specifications will find similar extended XHTML1.1 support, the modularization also allows for separate features to develop on their own timetable. So for example, XHTML1.1 will allow quicker migration to emerging XML standards such as MathML, in summary, the HTML4 specification primarily reined in all the various HTML implementations into a single clearly written specification based on SGML. XHTML1.0, ported this specification, as is, next, XHTML1.1 takes advantage of the extensible nature of XML and modularizes the whole specification. XHTML2.0 was intended to be the first step in adding new features to the specification in a standards-body-based approach. The WHATWG considers their work as living standard HTML for what constitutes the state of the art in major browser implementations by Apple, Google, Mozilla, Opera, hTML5 is specified by the HTML Working Group of the W3C following the W3C process. HTML lacks some of the found in earlier hypertext systems, such as source tracking, fat links
HTML
–
Tim Berners-Lee
HTML
–
HTML (HyperText Markup Language)
11.
Image
–
Images may be two-dimensional, such as a photograph or screen display, or three-dimensional, such as a statue or hologram. They may be captured by optical devices – such as cameras, mirrors, lenses, telescopes, microscopes, etc. and natural objects and phenomena, such as the human eye or water. The word image is used in the broader sense of any two-dimensional figure such as a map, a graph. A volatile image is one that only for a short period of time. This may be a reflection of an object by a mirror, a fixed image, also called a hard copy, is one that has been recorded on a material object, such as paper or textile by photography or any other digital process. A mental image exists in a mind, as something one remembers or imagines. The subject of an image need not be real, it may be a concept, such as a graph, function. For example, Sigmund Freud claimed to have dreamed purely in aural-images of dialogs, a still image is a single static image, as distinguished from a kinetic image. This phrase is used in photography, visual media and the industry to emphasize that one is not talking about movies. A film still is a taken on the set of a movie or television program during production. In literature, imagery is a picture which appeals to the senses. It can both be figurative and literal, a moving image is typically a movie or video, including digital video. It could also be an animated display such as a zoetrope, library of Congress – Format Descriptions for Still Images Image Processing – Online Open Research Group Legal Issues Regarding Images Image Copyright Case
Image
–
A man creating an image of himself, in the form of a painting
Image
–
An
SAR radar image acquired by the SIR-C/X-SAR radar on board the
Space Shuttle Endeavour shows the
Teide volcano. The city of Santa Cruz de Tenerife is visible as the purple and white area on the lower right edge of the island. Lava flows at the summit crater appear in shades of green and brown, while vegetation zones appear as areas of purple, green and yellow on the volcano's flanks.
12.
JavaScript
–
JavaScript is a high-level, dynamic, untyped, and interpreted programming language. It has been standardized in the ECMAScript language specification, JavaScript is prototype-based with first-class functions, making it a multi-paradigm language, supporting object-oriented, imperative, and functional programming styles. JavaScript was influenced by programming languages such as Self and Scheme, JavaScript is also used in environments that are not Web-based, such as PDF documents, site-specific browsers, and desktop widgets. Newer and faster JavaScript virtual machines and platforms built upon them have increased the popularity of JavaScript for server-side Web applications. On the client side, developers have traditionally implemented JavaScript as an interpreted language, programmers also use JavaScript in video-game development, in crafting desktop and mobile applications, and in server-side network programming with run-time environments such as Node. js. In 1994, a company called Mosaic Communications was founded in Mountain View, California, however, it intentionally shared no code with NCSA Mosaic. The internal codename for the browser was Mozilla, which stood for Mosaic killer. The first version of the Web browser, Mosaic Netscape 0.9, was released in late 1994, within four months it had already taken three-quarters of the browser market and became the main browser for Internet in the 1990s. To avoid trademark problems with the NCSA, the browser was subsequently renamed Netscape Navigator in the same year. Netscape Communications realized that the Web needed to more dynamic. In 1995, the company recruited Brendan Eich with the goal of embedding the Scheme programming language into its Netscape Navigator, to defend the idea of JavaScript against competing proposals, the company needed a prototype. Eich wrote one in 10 days, in May 1995, there is a common misconception that JavaScript was influenced by an earlier Web page scripting language developed by Nombas named C--. Brendan Eich, however, had never heard of C-- before he created LiveScript, Nombas did pitch their embedded Web page scripting to Netscape, though Web page scripting was not a new concept, as shown by the ViolaWWW Web browser. Nombas later switched to offering JavaScript instead of C-- in their ScriptEase product and was part of the TC39 group that standardized ECMAScript, in December 1995, soon after releasing JavaScript for browsers, Netscape introduced an implementation of the language for server-side scripting with Netscape Enterprise Server. Since the mid-2000s, additional server-side JavaScript implementations have been introduced, Microsoft script technologies including VBScript and JScript were released in 1996. JScript, an implementation of Netscapes JavaScript, was part of Internet Explorer 3. JScript was also available for server-side scripting in Internet Information Server, JavaScript began to acquire a reputation for being one of the roadblocks to a cross-platform and standards-driven Web. Some developers took on the task of trying to make their sites work in both major browsers, but many could not afford the time
JavaScript
–
JavaScript
13.
Dell
–
Dell Inc. is a multinational computer technology company based in Round Rock, Texas, United States, that develops, sells, repairs, and supports computers and related products and services. The company is a subsidiary of Dell Technologies, which was formed by the 2016 merger of Dell Inc. eponymously named after its founder, Michael Dell, the company is one of the largest technological corporations in the world, employing more than 103,300 people worldwide. Dell sells personal computers, servers, data storage devices, network switches, software, computer peripherals, HDTVs, cameras, printers, MP3 players, and electronics built by other manufacturers. Dell was a pure hardware vendor for much of its existence, Dell was listed at number 51 in the Fortune 500 list, until 2014. After going private in 2013, the confidential nature of its financial information prevents the company from being ranked by Fortune. In 2015, it was the third largest PC vendor in the world after Lenovo, Dell is currently the #1 shipper of PC monitors in the world. Dell is the sixth largest company in Texas by total revenue and it is the second largest non-oil company in Texas – behind AT&T – and the largest company in the Greater Austin area. It was a traded company, as well as a component of the NASDAQ-100 and S&P500. On September 7,2016, Dell Inc. acquired EMC Corporation to form Dell Technologies, Michael Dell founded PCs Limited while a student of the University of Texas at Austin. The dorm-room headquartered company sold IBM PC-compatible computers built from stock components, Dell dropped out of school to focus full-time on his fledgling business, after getting $1,000 in expansion-capital from his family. In 1985, the company produced the first computer of its own design, the Turbo PC, Dell appeared in PCs Limited advertisements in national magazines, asking readers to give us a chance to show you what can do. Selling directly to consumers custom-assembled computers according to a selection of options, in 1986, Michael Dell brought in Lee Walker, a 51-year-old venture capitalist, as president and chief operating officer, to serve as mentor and to implement Dells ideas for growing the company. Walker was also instrumental in recruiting members to the board of directors when the company went public in 1988, the company dropped the PC’s Limited name in 1987 to become Dell Computer Corporation and began expanding globally. In June 1988, Dells market capitalization grew by $30 million to $80 million from its June 22 initial public offering of 3.5 million shares at $8.50 a share. In 1992, Fortune magazine included Dell Computer Corporation in its list of the worlds 500 largest companies, making Michael Dell the youngest CEO of a Fortune 500 company ever. In 1993, to complement its own direct sales channel, Dell planned to sell PCs at big-box retail outlets such as Wal-Mart, bain consultant Kevin Rollins persuaded Michael Dell to pull out of these deals, believing they would be money losers in the long run. Margins at retail were thin at best and Dell left the channel in 1994. Rollins would soon join Dell full-time and eventually become the company President, Dell found an opportunity among PC-savvy individuals who liked the convenience of buying direct, customizing their PC to their means, and having it delivered in days
Dell
–
Dell Headquarters in
Round Rock, Texas
Dell
–
Dell logo, 2010–present
Dell
–
Dell's first logo from 1984 to 1989
Dell
–
The company sponsors
Dell Diamond, the home stadium of the
Round Rock Express, the AAA
minor league baseball affiliate of the
Texas Rangers major league baseball team
14.
Wikimedia Foundation
–
The Wikimedia Foundation, Inc. is an American non-profit and charitable organization headquartered in San Francisco, California. It is mostly known for participating in the Wikimedia movement and it owns the internet domain names of most movement projects and hosts sites like Wikipedia. The foundation was founded in 2003 by Jimmy Wales as a way to fund Wikipedia, as of 2015, the foundation employs over 280 people, with annual revenues in excess of US$75 million. Christophe Henner is chairman of the board, Katherine Maher is the executive director since March 2016. The Wikimedia Foundation has stated its goal is to develop and maintain open content, wiki-based projects, another main objective of the Wikimedia Foundation is political advocacy. The Wikimedia Foundation was granted section 501 status by the U. S, internal Revenue Code as a public charity in 2005. Its National Taxonomy of Exempt Entities code is B60, the foundations by-laws declare a statement of purpose of collecting and developing educational content and to disseminate it effectively and globally. In 2001, Jimmy Wales, an Internet entrepreneur, and Larry Sanger, the project was originally funded by Bomis, Wales for-profit business. As Wikipedias popularity skyrocketed, revenues to fund the project stalled, since Wikipedia was depleting Bomis resources, Wales and Sanger thought of a charity model to fund the project. The Wikimedia Foundation was incorporated in Florida on June 20,2003 and it applied to the United States Patent and Trademark Office to trademark Wikipedia on September 17,2004. The mark was granted status on January 10,2006. Trademark protection was accorded by Japan on December 16,2004, there were plans to license the use of the Wikipedia trademark for some products, such as books or DVDs. In April 2005, the U. S. Accordingly, the by-laws were amended to remove all reference to membership rights, the decision to change the bylaws was passed by the board unanimously. On September 25,2007, the board gave notice that the operations would be moving to the San Francisco Bay Area. Lila Tretikov was appointed director of the Wikimedia Foundation in May 2014. Former chief communications officer Katherine Maher was appointed the executive director. In addition to Wikipedia, the foundation operates other wikis that follow the free content model with their goal being the dissemination of knowledge. These include, Several additional projects exist to provide infrastructure or coordination of the free knowledge projects, for instance, a wiki helps coordinate work on MediaWiki software and Outreach gives guidelines for best practices on encouraging the use of Wikimedia sites
Wikimedia Foundation
–
Executive director
Lila Tretikov, 2014
Wikimedia Foundation
–
Logo of the Wikimedia Foundation
Wikimedia Foundation
–
Wikimedia Foundation servers
Wikimedia Foundation
–
Wikimedia Foundation and chapters finance meeting 2012, Paris
15.
Web browser
–
A web browser is a software application for retrieving, presenting and traversing information resources on the World Wide Web. An information resource is identified by a Uniform Resource Identifier that may be a web page, image, hyperlinks present in resources enable users easily to navigate their browsers to related resources. Although browsers are primarily intended to use the World Wide Web, the most popular web browsers are Google Chrome, Microsoft Edge, Safari, Opera and Firefox. The first web browser was invented in 1990 by Sir Tim Berners-Lee, Berners-Lee is the director of the World Wide Web Consortium, which oversees the Webs continued development, and is also the founder of the World Wide Web Foundation. His browser was called WorldWideWeb and later renamed Nexus, the first commonly available web browser with a graphical user interface was Erwise. The development of Erwise was initiated by Robert Cailliau, andreesens browser sparked the internet boom of the 1990s. The introduction of Mosaic in 1993 – one of the first graphical web browsers – led to an explosion in web use, Microsoft responded with its Internet Explorer in 1995, also heavily influenced by Mosaic, initiating the industrys first browser war. Bundled with Windows, Internet Explorer gained dominance in the web browser market, Internet Explorer usage share peaked at over 95% by 2002. Opera debuted in 1996, it has never achieved widespread use and it is also available on several other embedded systems, including Nintendos Wii video game console. In 1998, Netscape launched what was to become the Mozilla Foundation in an attempt to produce a competitive browser using the open source software model, as of August 2011, Firefox has a 28% usage share. Apples Safari had its first beta release in January 2003, as of April 2011, the most recent major entrant to the browser market is Chrome, first released in September 2008. Chromes take-up has increased year by year, by doubling its usage share from 8% to 16% by August 2011. This increase seems largely to be at the expense of Internet Explorer, in December 2011, Chrome overtook Internet Explorer 8 as the most widely used web browser but still had lower usage than all versions of Internet Explorer combined. Chromes user-base continued to grow and in May 2012, Chromes usage passed the usage of all versions of Internet Explorer combined, by April 2014, Chromes usage had hit 45%. Internet Explorer was deprecated in Windows 10, with Microsoft Edge replacing it as the web browser. The ways that web browser makers fund their development costs has changed over time, the first web browser, WorldWideWeb, was a research project. In addition to being freeware, Netscape Navigator and Opera were also sold commercially, Internet Explorer, on the other hand, was bundled free with the Windows operating system, and therefore it was funded partly by the sales of Windows to computer manufacturers and direct to users. Internet Explorer also used to be available for the Mac, in this respect, IE may have contributed to Windows and Microsoft applications sales in another way, through lock-in to Microsofts browser
Web browser
–
Marc Andreessen, inventor of Netscape
Web browser
–
Usage share of web browsers according to
StatCounter
Web browser
–
Some home media devices now include web browsers, like this
LG Smart TV. The browser is controlled using an on-screen keyboard and LG's "Magic Motion" remote.
16.
Web crawler
–
A Web crawler, sometimes called a spider, is an Internet bot that systematically browses the World Wide Web, typically for the purpose of Web indexing. Web search engines and some sites use Web crawling or spidering software to update their web content or indices of others sites web content. Web crawlers can copy all the pages they visit for later processing by an engine which indexes the downloaded pages so the users can search much more efficiently. Crawlers consume resources on the systems they visit and often visit sites without approval, issues of schedule, load, and politeness come into play when large collections of pages are accessed. Mechanisms exist for public sites not wishing to be crawled to make known to the crawling agent. For instance, including a robots. txt file can request bots to index only parts of a website, as the number of pages on the internet is extremely large, even the largest crawlers fall short of making a complete index. For that reason search engines were bad at giving relevant search results in the years of the World Wide Web. This is improved greatly by modern engines, nowadays very good results are given instantly. Crawlers can validate hyperlinks and HTML code and they can also be used for web scraping. A Web crawler may also be called a Web spider, an ant, a Web crawler starts with a list of URLs to visit, called the seeds. As the crawler visits these URLs, it all the hyperlinks in the page and adds them to the list of URLs to visit. URLs from the frontier are recursively visited according to a set of policies, if the crawler is performing archiving of websites it copies and saves the information as it goes. The archives are stored in such a way they can be viewed, read and navigated as they were on the live web. The archive is known as the repository and is designed to store, the repository only stores HTML pages and these pages are stored as distinct files. A repository is similar to any system that stores data. The only difference is that a repository does not need all the functionality offered by a database system, the repository stores the most recent version of the web page retrieved by the crawler. The large volume implies the crawler can only download a limited number of the Web pages within a given time, the high rate of change can imply the pages might have already been updated or even deleted. The number of possible URLs crawled being generated by server-side software has made it difficult for web crawlers to avoid retrieving duplicate content
Web crawler
–
Architecture of a Web crawler
17.
List of HTTP status codes
–
This is a list of Hypertext Transfer Protocol response status codes. It includes codes from IETF Request for Comments, other specifications, the first digit of the status code specifies one of five standard classes of responses. The message phrases shown are typical, but any human-readable alternative may be provided, unless otherwise stated, the status code is part of the HTTP/1.1 standard. The Internet Assigned Numbers Authority maintains the registry of HTTP status codes. An informational response indicates that the request was received and understood and it is issued on a provisional basis while request processing continues. It alerts the client to wait for a final response, the message consists only of the status line and optional header fields, and is terminated by an empty line. As the HTTP/1.0 standard did not define any 1xx status codes,100 Continue The server has received the request headers and the client should proceed to send the request body. Sending a large request body to a server after a request has been rejected for inappropriate headers would be inefficient. To have a check the requests headers, a client must send Expect, 100-continue as a header in its initial request. The response 417 Expectation Failed indicates the request should not be continued,101 Switching Protocols The requester has asked the server to switch protocols and the server has agreed to do so. 102 Processing A WebDAV request may contain many sub-requests involving file operations and this code indicates that the server has received and is processing the request, but no response is available yet. This prevents the client from timing out and assuming the request was lost and this class of status codes indicates the action requested by the client was received, understood, accepted, and processed successfully. 200 OK Standard response for successful HTTP requests, the actual response will depend on the request method used. In a GET request, the response will contain an entity corresponding to the requested resource, in a POST request, the response will contain an entity describing or containing the result of the action. 201 Created The request has been fulfilled, resulting in the creation of a new resource,202 Accepted The request has been accepted for processing, but the processing has not been completed. The request might or might not be acted upon. 203 Non-Authoritative Information The server is a proxy that received a 200 OK from its origin. 204 No Content The server successfully processed the request and is not returning any content,205 Reset Content The server successfully processed the request, but is not returning any content
List of HTTP status codes
–
404 error on German Wikipedia
18.
Secondary memory
–
In RAM devices data can be directly deleted or changed. It is used to store a large amount of data at lesser cost per byte than primary memory, secondary storage is two orders of magnitude less expensive than primary storage, the most common forms of auxiliary memory are flash memory, optical discs, magnetic disks and magnetic tape. The latest addition to the auxiliary memory family is flash memory and this form is much faster as compared to its predecessors, as this form of auxiliary memory does not involve any moving parts. In some laptops, this type of memory is referred to as a solid state drive. Flash memory, An electronic non-volatile computer storage device that can be erased and reprogrammed. Examples of this are flash drives, memory cards and solid state drives, a version of this is implemented in many notebook and some desktop computers. Optical disc, A storage medium from which data is read, optical disks can store much more data — up to 6 gigabytes more than most portable magnetic media, such as floppies. There are three types of optical disks, CD/DVD/BD-ROM, WORM & EO. Magnetic Disk, A magnetic disk is a circular plate constructed of metal or plastic coated with magnetized material, both sides of the disk are used and several disks may be stacked on one spindle with read/write heads available on each surface. Bits are stored on the surface in spots along concentric circles called tracks. Tracks are commonly divided into sections called sectors, Disk that are permanently attached and cannot be removed by the occasional user are called hard disks. A disk drive with removable disks is called a disk drive. Magnetic tapes, A magnetic tape transport consists of electric, mechanical and electronic components to provide the parts, the tape itself is a strip of plastic coated with a magnetic recording medium. Bits are recorded as magnetic spots on tape along several tracks, seven or nine bits are recorded to form a character together with a parity bit. R/W heads are mounted in each track so that data can be recorded, Computer data storage Secondary storage on the Computer data storage article Data storage device External storage Mass storage
Secondary memory
–
The bottom surface of a
compact disc, showing characteristic iridescence.
Secondary memory
–
USB flash drives, a type of secondary storage.
Secondary memory
–
A
hard disk drive with protective cover removed.
19.
Form (web)
–
A webform, web form or HTML form on a web page allows a user to enter data that is sent to a server for processing. Forms can resemble paper or database forms because web users fill out the forms using checkboxes, radio buttons, for example, forms can be used to enter shipping or credit card data to order a product, or can be used to retrieve search results from a search engine. Forms are enclosed in the HTML form tag and this tag specifies the communication endpoint the data entered into the form should be submitted to, and the method of submitting the data, GET or POST. For example, there are no equivalents to a box, tree view. A grid view, however, can be mimicked by using a standard HTML table with each containing a text input element. A tree view could also be mimicked through nested tables or, more semantically appropriately, in both cases, a server-side process is responsible for processing the information, while JavaScript handles the user-interaction. Implementations of these elements are available through JavaScript libraries such as jQuery. HTML5 introduces a number of tags that can be represented by other interface elements. Some are based upon text input fields and are intended to input and these include email to enter email addresses, tel for telephone numbers, number for numeric values. When data that has entered into HTML forms is submitted. Historically, a transport was also used. Another possible encoding, Internet media type multipart/form-data, is available and is common for POST-based file submissions. Forms are usually combined with programs written in programming language to allow developers to create dynamic web sites. The most popular languages include both client-side and/or server-side languages, the de facto client-side scripting language for web sites is JavaScript. Using JavaScript on the Document Object Model leads to the method of Dynamic HTML that allows creation and modification of a web page within the browser. While client-side languages used in conjunction with forms are limited, they often can serve to do pre-validation of the form data and/or to prepare the data to send to a server-side program. NET. PHP is one common language used for server-side programming and is one of the few languages created specifically for web programming. To use PHP with an HTML form, the URL of the PHP script is specified in the attribute of the form tag
Form (web)
–
Sample form. The form is enclosed in an
HTML table for visual layout.
20.
Server-side scripting
–
Server-side scripting is a technique used in web development which involves employing scripts on a web server which produce a response customized for each users request to the website. The alternative is for the web server itself to deliver a static web page, scripts can be written in any of a number of server-side scripting languages that are available. Server-side scripting is distinguished from client-side scripting where embedded scripts, such as JavaScript, are run client-side in a web browser, server-side scripting is often used to provide a customized interface for the user. These scripts may assemble client characteristics for use in customizing the response based on those characteristics, the users requirements, access rights, etc. A down-side to the use of server-side scripting is that the client needs to further requests over the network to the server in order to show new information to the user via the web browser. These requests can slow down the experience for the user, place more load on the server, when the server serves data in a commonly used manner, for example according to the HTTP or FTP protocols, users may have their choice of a number of client programs. In the case of more specialized applications, programmers may write their own server, client, and communications protocol, Netscape introduced an implementation of JavaScript for server-side scripting with Netscape Enterprise Server, first released in December,1994. Server-side scripting was later used in early 1995 by Fred DuFresne while developing the first web site for Boston, the technology is described in US patent 5835712. The patent was issued in 1998 and is now owned by Open Invention Network, in 2010 OIN named Fred DuFresne a Distinguished Inventor for his work on server-side scripting. Today, a variety of services use server-side scripting to deliver results back to a client as a paid or free service, an example would be WolframAlpha, which is a computational knowledge engine that computes results outside the clients environment and returns the computed result back. Apples Siri application also employs server-side scripting outside of a web application, the application takes an input, computes a result, and returns the result back to the client. In the earlier days of the web, server-side scripting was almost exclusively performed by using a combination of C programs, Perl scripts and those scripts were executed by the operating system, and the results were served back by the web server. Many modern web servers can directly execute on-line scripting languages such as ASP, JSP, Perl, PHP, for example, WebDNA includes its own embedded database system. Either form of scripting can be used to build up complex multi-page sites, dynamic websites sometimes use custom web application servers, such as Glassfish, Plack and Pythons Base HTTP Server library, although some may not consider this to be server-side scripting. When designing using dynamic web-based scripting techniques developers must have an understanding of the logical, temporal. For a users action to trigger the execution of code, for example. Creating such interactions can easily consume much development time and lead to unreadable code, server-side scripts are completely processed by the servers instead of clients. When clients request a page containing server-side scripts, the applicable server processes the scripts and returns an HTML page to the client
Server-side scripting
–
Dynamic web page: example of server-side scripting (PHP and MySQL).
21.
PHP
–
PHP is a server-side scripting language designed primarily for web development but also used as a general-purpose programming language. Originally created by Rasmus Lerdorf in 1994, the PHP reference implementation is now produced by The PHP Development Team, PHP originally stood for Personal Home Page, but it now stands for the recursive acronym PHP, Hypertext Preprocessor. PHP code may be embedded into HTML or HTML5 code, or it can be used in combination with various web template systems, web content management systems and web frameworks. PHP code is usually processed by a PHP interpreter implemented as a module in the web server or as a Common Gateway Interface executable. The web server combines the results of the interpreted and executed PHP code, PHP code may also be executed with a command-line interface and can be used to implement standalone graphical applications. The standard PHP interpreter, powered by the Zend Engine, is free software released under the PHP License, PHP has been widely ported and can be deployed on most web servers on almost every operating system and platform, free of charge. The PHP language evolved without a formal specification or standard until 2014. Since 2014 work has gone on to create a formal PHP specification, PHP development began in 1995 when Rasmus Lerdorf wrote several Common Gateway Interface programs in C, which he used to maintain his personal homepage. He extended them to work with web forms and to communicate with databases, PHP/FI could help to build simple, dynamic web applications. This release already had the functionality that PHP has as of 2013. This included Perl-like variables, form handling, and the ability to embed HTML, the syntax resembled that of Perl but was simpler, more limited and less consistent. A development team began to form and, after months of work and beta testing, the fact that PHP lacked an original overall design but instead developed organically has led to inconsistent naming of functions and inconsistent ordering of their parameters. Zeev Suraski and Andi Gutmans rewrote the parser in 1997 and formed the base of PHP3, changing the name to the recursive acronym PHP. Afterwards, public testing of PHP3 began, and the launch came in June 1998. Suraski and Gutmans then started a new rewrite of PHPs core and they also founded Zend Technologies in Ramat Gan, Israel. On May 22,2000, PHP4, powered by the Zend Engine 1.0, was released, as of August 2008 this branch reached version 4.4.9. PHP4 is no longer under development nor will any security updates be released, on July 13,2004, PHP5 was released, powered by the new Zend Engine II. PHP5 included new features such as improved support for object-oriented programming, the PHP Data Objects extension, in 2008 PHP5 became the only stable version under development
PHP
–
Rasmus Lerdorf, who wrote the original
Common Gateway Interface (CGI) component, together with
Andi Gutmans and
Zeev Suraski, who rewrote the
parser that formed PHP 3.
PHP
–
PHP
PHP
PHP
22.
Dynamic web page
–
A server-side dynamic web page is a web page whose construction is controlled by an application server processing server-side scripts. In server-side scripting, parameters determine how the assembly of new web page proceeds. A client-side dynamic web page processes the web page using HTML scripting running in the browser as it loads, JavaScript and other scripting languages determine the way the HTML in the received page is parsed into the Document Object Model, or DOM, that represents the loaded web page. The same client-side techniques can then dynamically update or change the DOM in the same way, a dynamic web page is then reloaded by the user or by a computer program to change some variable content. The updating information could come from the server, or from changes made to that pages DOM, using Ajax technologies the end user gets one dynamic page managed as a single page in the web browser while the actual web content rendered on that page can vary. The Ajax engine sits only on the browser requesting parts of its DOM, DHTML is the umbrella term for technologies and methods used to create web pages that are not static web pages. Client-side-scripting, server-side scripting, or a combination of these make for the web experience in a browser. Classical hypertext navigation, with HTML or XHTML alone, provides static content, meaning that the user requests a web page and simply views the page, however, a web page can also provide a live, dynamic, or interactive user experience. Content on a web page can change, in response to different contexts or conditions, in this case the dynamic behavior occurs within the presentation. Using server-side scripting to change the page source between pages, adjusting the sequence or reload of the web pages or web content supplied to the browser. Server responses may be determined by such conditions as data in a posted HTML form, parameters in the URL, the type of browser being used, web pages that use client-side scripting must use presentation technology broadly called rich interfaced pages. Client-side scripting languages like JavaScript or ActionScript, used for Dynamic HTML, the scripting also allows use of remote scripting, a technique by which the DHTML page requests additional information from a server, using a hidden Frame, XMLHttpRequests, or a web service. Web pages that use server-side scripting are often created with the help of server-side languages such as PHP, Perl, ASP, ASP. NET, JSP, ColdFusion and these server-side languages typically use the Common Gateway Interface to produce dynamic web pages. These kinds of pages can also use, on the client-side, the web browsers explosion started with 1993s Mosaic. It is obvious, however, that the concept of dynamically driven websites predates the internet, the introduction of JavaScript enabled the production of dynamic web pages Execusite introduced the first dynamic website solution for the professional marketplace in June 1997. Execusite was acquired by Website Pros in January 2000, during the bust cycle of the Dot-com bubble, the original Execusite founders bought back the company from Website Pros. Execusite was later acquired by Wolters-Kluwer in December 2001 and was re-branded as CCH Site Builder, a program running on a web server is used to generate the web content on various web pages, manage user sessions, and control workflow. Server responses may be determined by such conditions as data in a posted HTML form, parameters in the URL, the type of browser being used and these server-side languages often use the Common Gateway Interface to produce dynamic web pages
Dynamic web page
–
A dynamic web page needs a support-server, an
application server to process its server-side language.
23.
Database
–
A database is an organized collection of data. It is the collection of schemas, tables, queries, reports, views, a database management system is a computer software application that interacts with the user, other applications, and the database itself to capture and analyze data. A general-purpose DBMS is designed to allow the definition, creation, querying, update, well-known DBMSs include MySQL, PostgreSQL, MongoDB, MariaDB, Microsoft SQL Server, Oracle, Sybase, SAP HANA, MemSQL and IBM DB2. Sometimes a DBMS is loosely referred to as a database, formally, a database refers to a set of related data and the way it is organized. The DBMS provides various functions that allow entry, storage and retrieval of large quantities of information, because of the close relationship between them, the term database is often used casually to refer to both a database and the DBMS used to manipulate it. Outside the world of information technology, the term database is often used to refer to any collection of related data. This article is concerned only with databases where the size and usage requirements necessitate use of a management system. Update – Insertion, modification, and deletion of the actual data, retrieval – Providing information in a form directly usable or for further processing by other applications. The retrieved data may be available in a form basically the same as it is stored in the database or in a new form obtained by altering or combining existing data from the database. Both a database and its DBMS conform to the principles of a database model. Database system refers collectively to the model, database management system. Physically, database servers are dedicated computers that hold the actual databases and run only the DBMS, Database servers are usually multiprocessor computers, with generous memory and RAID disk arrays used for stable storage. RAID is used for recovery of data if any of the disks fail, hardware database accelerators, connected to one or more servers via a high-speed channel, are also used in large volume transaction processing environments. DBMSs are found at the heart of most database applications, DBMSs may be built around a custom multitasking kernel with built-in networking support, but modern DBMSs typically rely on a standard operating system to provide these functions. Since DBMSs comprise a significant market, computer and storage vendors often take into account DBMS requirements in their own development plans, databases are used to support internal operations of organizations and to underpin online interactions with customers and suppliers. Databases are used to hold information and more specialized data. A DBMS has evolved into a software system and its development typically requires thousands of human years of development effort. Some general-purpose DBMSs such as Adabas, Oracle and DB2 have been undergoing upgrades since the 1970s, general-purpose DBMSs aim to meet the needs of as many applications as possible, which adds to the complexity
Database
–
Collage of five types of database models
Database
–
Basic structure of navigational
CODASYL database model
24.
Dynamic content
–
A server-side dynamic web page is a web page whose construction is controlled by an application server processing server-side scripts. In server-side scripting, parameters determine how the assembly of new web page proceeds. A client-side dynamic web page processes the web page using HTML scripting running in the browser as it loads, JavaScript and other scripting languages determine the way the HTML in the received page is parsed into the Document Object Model, or DOM, that represents the loaded web page. The same client-side techniques can then dynamically update or change the DOM in the same way, a dynamic web page is then reloaded by the user or by a computer program to change some variable content. The updating information could come from the server, or from changes made to that pages DOM, using Ajax technologies the end user gets one dynamic page managed as a single page in the web browser while the actual web content rendered on that page can vary. The Ajax engine sits only on the browser requesting parts of its DOM, DHTML is the umbrella term for technologies and methods used to create web pages that are not static web pages. Client-side-scripting, server-side scripting, or a combination of these make for the web experience in a browser. Classical hypertext navigation, with HTML or XHTML alone, provides static content, meaning that the user requests a web page and simply views the page, however, a web page can also provide a live, dynamic, or interactive user experience. Content on a web page can change, in response to different contexts or conditions, in this case the dynamic behavior occurs within the presentation. Using server-side scripting to change the page source between pages, adjusting the sequence or reload of the web pages or web content supplied to the browser. Server responses may be determined by such conditions as data in a posted HTML form, parameters in the URL, the type of browser being used, web pages that use client-side scripting must use presentation technology broadly called rich interfaced pages. Client-side scripting languages like JavaScript or ActionScript, used for Dynamic HTML, the scripting also allows use of remote scripting, a technique by which the DHTML page requests additional information from a server, using a hidden Frame, XMLHttpRequests, or a web service. Web pages that use server-side scripting are often created with the help of server-side languages such as PHP, Perl, ASP, ASP. NET, JSP, ColdFusion and these server-side languages typically use the Common Gateway Interface to produce dynamic web pages. These kinds of pages can also use, on the client-side, the web browsers explosion started with 1993s Mosaic. It is obvious, however, that the concept of dynamically driven websites predates the internet, the introduction of JavaScript enabled the production of dynamic web pages Execusite introduced the first dynamic website solution for the professional marketplace in June 1997. Execusite was acquired by Website Pros in January 2000, during the bust cycle of the Dot-com bubble, the original Execusite founders bought back the company from Website Pros. Execusite was later acquired by Wolters-Kluwer in December 2001 and was re-branded as CCH Site Builder, a program running on a web server is used to generate the web content on various web pages, manage user sessions, and control workflow. Server responses may be determined by such conditions as data in a posted HTML form, parameters in the URL, the type of browser being used and these server-side languages often use the Common Gateway Interface to produce dynamic web pages
Dynamic content
–
Dynamic web page: example of server-side scripting (PHP and MySQL).
25.
Embedded system
–
An embedded system is a computer system with a dedicated function within a larger mechanical or electrical system, often with real-time computing constraints. It is embedded as part of a device often including hardware. Embedded systems control many devices in use today. Ninety-eight percent of all microprocessors are manufactured as components of embedded systems, examples of properties of typically embedded computers when compared with general-purpose counterparts are low power consumption, small size, rugged operating ranges, and low per-unit cost. This comes at the price of limited processing resources, which make them more difficult to program. For example, intelligent techniques can be designed to power consumption of embedded systems. Modern embedded systems are based on microcontrollers, but ordinary microprocessors are also common. In either case, the processor used may be ranging from general purpose to those specialised in certain class of computations. A common standard class of dedicated processors is the signal processor. Since the embedded system is dedicated to tasks, design engineers can optimize it to reduce the size and cost of the product and increase the reliability. Some embedded systems are mass-produced, benefiting from economies of scale, complexity varies from low, with a single microcontroller chip, to very high with multiple units, peripherals and networks mounted inside a large chassis or enclosure. One of the very first recognizably modern embedded systems was the Apollo Guidance Computer, an early mass-produced embedded system was the Autonetics D-17 guidance computer for the Minuteman missile, released in 1961. When the Minuteman II went into production in 1966, the D-17 was replaced with a new computer that was the first high-volume use of integrated circuits. Since these early applications in the 1960s, embedded systems have come down in price and there has been a rise in processing power. An early microprocessor for example, the Intel 4004, was designed for calculators and other systems but still required external memory. By the early 1980s, memory, input and output system components had been integrated into the chip as the processor forming a microcontroller. Microcontrollers find applications where a computer would be too costly. A comparatively low-cost microcontroller may be programmed to fulfill the role as a large number of separate components
Embedded system
–
Picture of the internals of an
ADSL modem /
router. A modern example of an embedded system. Labelled parts include a
microprocessor (4),
RAM (6), and
flash memory (7).
Embedded system
–
Embedded Computer Sub-Assembly for Accupoll Electronic Voting Machine
Embedded system
–
Gumstix Overo COM, a tiny,
OMAP -based embedded
computer-on-module with
Wifi and
Bluetooth.
Embedded system
–
e-con Systems eSOM270 & eSOM300 Computer on Modules
26.
Printer (computing)
–
In computing, a printer is a peripheral which makes a persistent human-readable representation of graphics or text on paper or similar physical media. The worlds first computer printer was a 19th-century mechanically driven apparatus invented by Charles Babbage for his difference engine, the plotter was used for those requiring high quality line art like blueprints. Laser printers using PostScript mixed text and graphics, like dot-matrix printers, by 1990, most simple printing tasks like fliers and brochures were now created on personal computers and then laser printed, expensive offset printing systems were being dumped as scrap. The HP Deskjet of 1988 offered the same advantages as laser printer in terms of flexibility, inkjet systems rapidly displaced dot matrix and daisy wheel printers from the market. By the 2000s high-quality printers of this sort had fallen under the price point. Even the desire for printed output for offline reading while on mass transit or aircraft has been displaced by e-book readers, today, traditional printers are being used more for special purposes, like printing photographs or artwork, and are no longer a must-have peripheral. Starting around 2010, 3D printing became an area of intense interest and these devices are in their earliest stages of development and have not yet become commonplace. Personal printers are designed to support individual users, and may be connected to only a single computer. These printers are designed for low-volume, short-turnaround print jobs, requiring minimal setup time to produce a copy of a given document. However, they are generally slow devices ranging from 6 to around 25 pages per minute, however, this is offset by the on-demand convenience. Some printers can print documents stored on cards or from digital cameras. Networked or shared printers are designed for high-volume, high-speed printing and they are usually shared by many users on a network and can print at speeds of 45 to around 100 ppm. The Xerox 9700 could achieve 120 ppm, a virtual printer is a piece of computer software whose user interface and API resembles that of a printer driver, but which is not connected with a physical computer printer. It is called a printer by analogy with a printer which produces a two-dimensional document by a similar process of depositing a layer of ink on paper. The choice of print technology has an effect on the cost of the printer and cost of operation, speed, quality and permanence of documents. Some printer technologies dont work with certain types of physical media, cheques can be printed with liquid ink or on special cheque paper with toner anchorage so that alterations may be detected. The machine-readable lower portion of a cheque must be printed using MICR toner or ink, banks and other clearing houses employ automation equipment that relies on the magnetic flux from these specially printed characters to function properly. The following printing technologies are found in modern printers, A laser printer rapidly produces high quality text
Printer (computing)
–
HP LaserJet 5 printer
Printer (computing)
–
The Game Boy Pocket Printer, a
thermal printer released as a peripheral for the
Nintendo Game Boy
Printer (computing)
–
This is an example of a wide-carriage
dot matrix printer, designed for 14-inch (360 mm) wide paper, shown with 8.5-by-14-inch (220 mm × 360 mm) legal paper. Wide carriage printers were often used in the field of businesses, to print accounting records on 11-by-14-inch (280 mm × 360 mm)
tractor-feed paper. They were also called "132-column printers"
Printer (computing)
–
Liquid ink cartridge from Hewlett-Packard HP 845C inkjet printer
27.
Router (computing)
–
A router is a networking device that forwards data packets between computer networks. Routers perform the traffic directing functions on the Internet, a data packet is typically forwarded from one router to another router through the networks that constitute the internetwork until it reaches its destination node. A router is connected to two or more lines from different networks. When a data packet comes in on one of the lines, then, using information in its routing table or routing policy, it directs the packet to the next network on its journey. The most familiar type of routers are home and small office routers that simply pass IP packets between the computers and the Internet. An example of a router would be the cable or DSL router. Though routers are typically dedicated hardware devices, software-based routers also exist, when multiple routers are used in interconnected networks, the routers can exchange information about destination addresses using a dynamic routing protocol. Each router builds up a table listing the preferred routes between any two systems on the interconnected networks. A router may have interfaces for different physical types of connections, such as copper cables, fibre optic. Its firmware can also support different networking communications protocol standards, each network interface is used by this specialized computer software to enable data packets to be forwarded from one protocol transmission system to another. Routers may also be used to two or more logical groups of computer devices known as subnets, each with a different network prefix. The network prefixes recorded in the table do not necessarily map directly to the physical interface connections. It does this using internal pre-configured directives, called static routes, static and dynamic routes are stored in the Routing Information Base. The control-plane logic then strips non-essential directives from the RIB and builds a Forwarding Information Base to be used by the forwarding-plane, Forwarding plane, The router forwards data packets between incoming and outgoing interface connections. It routes them to the network type using information that the packet header contains. It uses data recorded in the routing control plane. Routers may provide connectivity within enterprises, between enterprises and the Internet, or between internet service providers networks, the largest routers interconnect the various ISPs, or may be used in large enterprise networks. Smaller routers usually provide connectivity for typical home and office networks, other networking solutions may be provided by a backbone Wireless Distribution System, which avoids the costs of introducing networking cables into buildings
Router (computing)
–
A typical home or small office router showing the
ADSL telephone line and
Ethernet network cable connections
Router (computing)
–
A Cisco ASM/2-32EM router deployed at
CERN in 1987
Router (computing)
–
Avaya ERS 8600 (2010)
28.
Webcam
–
A webcam is a video camera that feeds or streams its image in real time to or through a computer to a computer network. When captured by the computer, the stream may be saved, viewed or sent on to other networks via systems such as the internet. When sent to a location, the video stream may be saved, viewed or on sent there. Unlike an IP camera, a webcam is generally connected by a USB cable, or similar cable, or built into computer hardware, some of them, for example, those used as online traffic cameras, are expensive, rugged professional video cameras. Webcams are known for their low manufacturing cost and their high flexibility and they have also become a source of security and privacy issues, as some built-in webcams can be remotely activated by spyware. The most popular use of webcams is the establishment of video links, other popular uses include security surveillance, computer vision, video broadcasting, and for recording social videos. Researchers claim that this method is accurate to ±5 bpm, Webcams may be installed at places such as childcare centres, offices, shops and private areas to monitor security and general activity. Webcams have been used for augmented reality experiences online, one such function has the webcam act as a magic mirror to allow an online shopper to view a virtual item on themselves. The Webcam Social Shopper is one example of software that utilizes the webcam in this manner, improved video quality has helped webcams encroach on traditional video conferencing systems. Webcam features and performance can vary by program, computer operating system, video calling support has also been added to several popular instant messaging programs. Webcams can be used as security cameras, software is available to allow PC-connected cameras to watch for movement and sound, recording both when they are detected. These recordings can then be saved to the computer, e-mailed, unauthorized access of webcams can present significant privacy issues. In December 2011, Russia announced that 290,000 Webcams would be installed in 90,000 polling stations to monitor the Russian presidential election,2012, Webcams can be used to take video clips and still pictures. Various software tools in use can be employed for this, such as PicMaster, Photo Booth. For a more complete list see Comparison of webcam software, special software can use the video stream from a webcam to assist or enhance a users control of applications and games. Video features, including faces, shapes, models and colors can be observed and tracked to produce a form of control. This can be applied to games, providing additional control, improved interactivity, by removing the IR filter of the webcam, IR LEDs can be used, which has the advantage of being invisible to the naked eye, removing a distraction from the user. TrackIR is a version of this technology
Webcam
–
Typical low-cost webcam used with many personal computers
Webcam
–
Webcams typically include a lens (shown at top), an image sensor (shown at bottom), and supporting circuitry.
29.
Local area network
–
By contrast, a wide area network, not only covers a larger geographic distance, but also generally involves leased telecommunication circuits or Internet links. An even greater contrast is the Internet, which is a system of globally connected business, Ethernet and Wi-Fi are the two most common transmission technologies in use for local area networks. Historical technologies include ARCNET, Token ring, and AppleTalk, the increasing demand and use of computers in universities and research labs in the late 1960s generated the need to provide high-speed interconnections between computer systems. A1970 report from the Lawrence Radiation Laboratory detailing the growth of their Octopus network gave an indication of the situation. A number of experimental and early commercial LAN technologies were developed in the 1970s, Cambridge Ring was developed at Cambridge University starting in 1974. Ethernet was developed at Xerox PARC in 1973–1975, and filed as U. S, in 1976, after the system was deployed at PARC, Robert Metcalfe and David Boggs published a seminal paper, Ethernet, Distributed Packet-Switching for Local Computer Networks. ARCNET was developed by Datapoint Corporation in 1976 and announced in 1977 and it had the first commercial installation in December 1977 at Chase Manhattan Bank in New York. The initial driving force for networking was generally to share storage and printers, there was much enthusiasm for the concept and for several years, from about 1983 onward, computer industry pundits would regularly declare the coming year to be, “The year of the LAN”. In practice, the concept was marred by proliferation of incompatible physical layer and network protocol implementations, typically, each vendor would have its own type of network card, cabling, protocol, and network operating system. Netware dominated the personal computer LAN business from early after its introduction in 1983 until the mid-1990s when Microsoft introduced Windows NT Advanced Server, of the competitors to NetWare, only Banyan Vines had comparable technical strengths, but Banyan never gained a secure base. During the same period, Unix workstations were using TCP/IP networking, early LAN cabling had generally been based on various grades of coaxial cable. This led to the development of 10BASE-T and structured cabling which is still the basis of most commercial LANs today, while fiber-optic cabling is common for links between switches, use of fiber to the desktop is rare. Many LANs use wireless technologies that are built into Smartphones, tablet computers, in a wireless local area network, users may move unrestricted in the coverage area. Wireless networks have become popular in residences and small businesses, because of their ease of installation, guests are often offered Internet access via a hotspot service. Network topology describes the layout of interconnections between devices and network segments, at the data link layer and physical layer, a wide variety of LAN topologies have been used, including ring, bus, mesh and star. At the higher layers, NetBEUI, IPX/SPX, AppleTalk and others were once common, simple LANs generally consist of cabling and one or more switches. A switch can be connected to a router, cable modem, a LAN can include a wide variety of other network devices such as firewalls, load balancers, and network intrusion detection. LANs can maintain connections with other LANs via leased lines, leased services, depending on how the connections are established and secured, and the distance involved, such linked LANs may also be classified as a metropolitan area network or a wide area network
Local area network
–
A conceptual diagram of a local area network using
10BASE5 Ethernet
30.
Operating system
–
An operating system is system software that manages computer hardware and software resources and provides common services for computer programs. All computer programs, excluding firmware, require a system to function. Operating systems are found on many devices that contain a computer – from cellular phones, the dominant desktop operating system is Microsoft Windows with a market share of around 83. 3%. MacOS by Apple Inc. is in place, and the varieties of Linux is in third position. Linux distributions are dominant in the server and supercomputing sectors, other specialized classes of operating systems, such as embedded and real-time systems, exist for many applications. A single-tasking system can run one program at a time. Multi-tasking may be characterized in preemptive and co-operative types, in preemptive multitasking, the operating system slices the CPU time and dedicates a slot to each of the programs. Unix-like operating systems, e. g. Solaris, Linux, cooperative multitasking is achieved by relying on each process to provide time to the other processes in a defined manner. 16-bit versions of Microsoft Windows used cooperative multi-tasking, 32-bit versions of both Windows NT and Win9x, used preemptive multi-tasking. Single-user operating systems have no facilities to distinguish users, but may allow multiple programs to run in tandem, a distributed operating system manages a group of distinct computers and makes them appear to be a single computer. The development of networked computers that could be linked and communicate with each other gave rise to distributed computing, distributed computations are carried out on more than one machine. When computers in a work in cooperation, they form a distributed system. The technique is used both in virtualization and cloud computing management, and is common in large server warehouses, embedded operating systems are designed to be used in embedded computer systems. They are designed to operate on small machines like PDAs with less autonomy and they are able to operate with a limited number of resources. They are very compact and extremely efficient by design, Windows CE and Minix 3 are some examples of embedded operating systems. A real-time operating system is a system that guarantees to process events or data by a specific moment in time. A real-time operating system may be single- or multi-tasking, but when multitasking, early computers were built to perform a series of single tasks, like a calculator. Basic operating system features were developed in the 1950s, such as resident monitor functions that could run different programs in succession to speed up processing
Operating system
–
OS/360 was used on most IBM mainframe computers beginning in 1966, including computers used by the
Apollo program.
Operating system
Operating system
–
The
first server for the
World Wide Web ran on NeXTSTEP, based on BSD
31.
NeXT Computer
–
The NeXT Computer is a workstation computer developed, marketed, and sold by NeXT Inc. It runs the Mach- and BSD-derived, Unix-based NeXTSTEP operating system, the motherboard is square and fits into one of four identical slots in the enclosure. The NeXT Computer enclosure consists of a 1-foot die-cast magnesium cube-shaped, black case and it was launched in 1988 at US$6,500. The NeXT Computer was succeeded by the NeXTcube, an upgraded model and this event gave developers interested in developing NeXT software an insight into the software architecture, object-oriented programming, and developing for the NeXT Computer. The luncheon speaker was Steve Jobs, citing as truly innovative the optical drive, DSP, and object-oriented programming environment, the magazine concluded that the NeXT Computer is worth every penny of its $6500 market price. It was, however, not a significant commercial success, failing to reach the level of volume sales like the Apple II, Commodore 64. The workstations were sold to universities, financial institutions, and government agencies, issue #3 was first demonstrated to Steve Jobs at NeXTWorld Expo 1993. com — NeXTcube Photos of black hardware A fun fact and one of Steve Jobs quirks. All the components in the including the PCB and connectors had to be black in color. PCBs were typically green from the mask that was applied. A process of pad capping was developed to allow the black oxide from the layers to be seen. Even the euro card connector had to be molded in black which where typically grey. The mounting hardware had to be black oxide. etc
NeXT Computer
–
NeXT Computer used by
Berners-Lee at
CERN
32.
Cobalt Qube
–
The Cobalt Qube was a computer server appliance product line developed by Cobalt Networks, Inc. featuring a modified Red Hat Linux operating system and a proprietary GUI for server management. The original Qube systems were equipped with RM5230 or RM5231 microprocessors, netBSD operating system has been ported to both the Cobalt Qube and RaQ. The Qube 2700 was the first product released by Cobalt Networks in 1998, mark Orr, one of the Cobalt Networks CEOs, came up with the cobalt color. The green LED in the front was Bill Scotts idea, the 2700 was not a development version number but came from the atomic number of cobalt,27. The Qube 2700 used the RM5230 microprocessor, the next product was called the Qube 2800 before being sold. But, released in 2000, was called the Qube 2. The Qube 2 used the RM5231 microprocessor, under an OEM arrangement, the Qube 2 units were also produced by Gateway in the form of the Gateway Micro Server. The casing featured on these units was black instead of cobalt blue, the Qube 3, released in 2002, used an AMD K6-2 CPU at either 300 MHz or 450 MHz and was the last product in the Qube line. A fourth Qube model was in development but was never released, however, several models were released in the data center-friendly Cobalt RaQ product line after the Cobalt Qube was discontinued
Cobalt Qube
–
Qube 3 front
Cobalt Qube
–
Qube 3 back; this model lacks an external
SCSI port.
33.
Server appliance
–
A computer appliance is a computer with software or firmware that is specifically designed to provide a specific computing resource. Such devices became known as appliances because of the similarity in role or management to an appliance, which are generally closed and sealed. The hardware and software are delivered as a product and may even be pre-configured before delivery to a customer. Unlike general purpose computers, appliances are not designed to allow the customers to change the software. Traditionally, software applications run on top of a operating system. The main issue with the model is related to complexity. It is complex to integrate the system and applications with a hardware platform. By tightly constraining the variations of the hardware and software, the appliance becomes easily deployable, additionally, when problems and errors appear, the supporting staff very rarely needs to explore them deeply to understand the matter thoroughly. The staff needs merely training on the management software to be able to resolve most of problems. In all forms of the computer model, customers benefit from easy operations. The appliance has exactly one combination of hardware and operating system and application software and this prevents customers from needing to perform complex integration work, and dramatically simplifies troubleshooting. In fact, this turnkey operation characteristic is the benefit that customers seek when purchasing appliances. To be considered an appliance, the needs to be integrated with software. This distinguishes appliances from home grown solutions, or solutions requiring complex implementations by integrators or Value-added resellers, the appliance approach helps to decouple the various systems and applications, for example in the data center. Once a resource is decoupled, in theory it can be centralized to become shared among many systems, centrally managed and optimized. The variety of computer appliances reflects the range of computing resources they provide to applications. They are often a gateway to a full DRaaS solution, firewall- and Security appliances computer appliances that are designed to protect computer networks from unwanted traffic. In essence, the distribution or the firmware that is running a computer appliance
Server appliance
–
Snap Server 650
Server appliance
–
Cobalt Qube 3
34.
Sir Tim Berners-Lee
–
Sir Timothy John Berners-Lee OM KBE FRS FREng FRSA FBCS, also known as TimBL, is an English computer scientist, best known as the inventor of the World Wide Web. Berners-Lee is the director of the World Wide Web Consortium, which oversees the development of the Web. He is also the founder of the World Wide Web Foundation and is a researcher and holder of the founders chair at the MIT Computer Science. He is a director of the Web Science Research Initiative, in 2011, he was named as a member of the board of trustees of the Ford Foundation. In 2004, Berners-Lee was knighted by Queen Elizabeth II for his pioneering work, in April 2009, he was elected a foreign associate of the United States National Academy of Sciences. Named in Time magazines list of the 100 Most Important People of the 20th century and he tweeted This is for everyone, which instantly was spelled out in LCD lights attached to the chairs of the 80,000 people in the audience. On 4 April 2017, Berners-Lee received the 2016 Turing Award for inventing the World Wide Web, the first web browser, Berners-Lee was born in London, England, United Kingdom, one of four children born to Mary Lee Woods and Conway Berners-Lee. His parents worked on the first commercially built computer, the Ferranti Mark 1, a keen trainspotter as a child, he learnt about electronics from tinkering with a model railway. He studied at The Queens College, Oxford, from 1973 to 1976, after graduation, Berners-Lee worked as an engineer at the telecommunications company Plessey in Poole, Dorset. In 1978, he joined D. G. Nash in Ferndown, Dorset, Berners-Lee worked as an independent contractor at CERN from June to December 1980. While in Geneva, he proposed a project based on the concept of hypertext, to demonstrate it, he built a prototype system named ENQUIRE. After leaving CERN in late 1980, he went to work at John Pooles Image Computer Systems, Ltd, in Bournemouth and he ran the companys technical side for three years. The project he worked on was a remote procedure call which gave him experience in computer networking. In 1984, he returned to CERN as a fellow and it then was accepted by his manager, Mike Sendall. He used similar ideas to those underlying the ENQUIRE system to create the World Wide Web, for which he designed and his software also functioned as an editor, and the first Web server, CERN HTTPd. The first web site was built at CERN, despite this being an international organisation hosted by Switzerland, the office that Berners-Lee used was just across the border in France. It was put online on 6 August 1991 for the first time, It provided an explanation of what the World Wide Web was and we can connect with each other instantly, all over the world. In 1994, Berners-Lee founded the W3C at the Massachusetts Institute of Technology and it comprised various companies that were willing to create standards and recommendations to improve the quality of the Web
Sir Tim Berners-Lee
–
Berners-Lee in 2014.
Sir Tim Berners-Lee
–
Berners-Lee, 2005
Sir Tim Berners-Lee
–
Berners-Lee using his laptop in 2003
Sir Tim Berners-Lee
–
Berners-Lee's tweet, "This is for everyone", at the
2012 Summer Olympic Games in London
35.
CERN
–
The European Organization for Nuclear Research, known as CERN, is a European research organization that operates the largest particle physics laboratory in the world. Established in 1954, the organization is based in a northwest suburb of Geneva on the Franco–Swiss border, Israel is the only non-European country granted full membership. The main site at Meyrin hosts a large computing facility, which is used to store and analyse data from experiments. Researchers need remote access to facilities, so the lab has historically been a major wide area network hub. CERN is also the birthplace of the World Wide Web, the convention establishing CERN was ratified on 29 September 1954 by 12 countries in Western Europe. The acronym was retained for the new laboratory after the council was dissolved. CERNs first president was Sir Benjamin Lockspeiser, edoardo Amaldi was the general secretary of CERN at its early stages when operations were still provisional, while the first Director-General was Felix Bloch. The laboratory was originally devoted to study of nuclei, but was soon applied to higher-energy physics. Therefore, the laboratory operated by CERN is commonly referred to as the European laboratory for particle physics, several important achievements in particle physics have been made through experiments at CERN. The 1984 Nobel Prize for Physics was awarded to Carlo Rubbia, the 1992 Nobel Prize for Physics was awarded to CERN staff researcher Georges Charpak for his invention and development of particle detectors, in particular the multiwire proportional chamber. The World Wide Web began as a CERN project named ENQUIRE, initiated by Tim Berners-Lee in 1989, Berners-Lee and Cailliau were jointly honoured by the Association for Computing Machinery in 1995 for their contributions to the development of the World Wide Web. Based on the concept of hypertext, the project was intended to facilitate sharing of information among researchers, the first website was activated in 1991. On 30 April 1993, CERN announced that the World Wide Web would be free to anyone, a copy of the original first webpage, created by Berners-Lee, is still published on the World Wide Web Consortiums website as a historical document. Prior to the Webs development, CERN had pioneered the introduction of Internet technology, a short history of this period can be found at CERN. ch. More recently, CERN has become a facility for the development of computing, hosting projects including the Enabling Grids for E-sciencE. It also hosts the CERN Internet Exchange Point, one of the two main internet exchange points in Switzerland. 48×10−5, a measurement with 6. 0-sigma significance. However, on 23 February, CERN stated in a release that the results were flawed due to an incorrectly connected GPS-synchronization cable. In March 2012, the ICARUS Collaboration reported that the measurement would be reproduced by both OPERA and ICARUS, further tests, after fixing the GPS connector, showed speed measurements consistent with the speed of light from four experiments at Gran Sasso, including OPERA
CERN
–
European Organization for Nuclear Research Organisation européenne pour la recherche nucléaire
CERN
–
The 12 founding member states of CERN in 1954 (map borders from 1954-1990)
CERN
–
This
NeXT Computer used by British scientist
Sir Tim Berners-Lee at CERN became the first
Web server.
CERN
–
This
Cisco Systems router at CERN was one of the first
IP routers deployed in Europe.
36.
Hypertext
–
Hypertext documents are interconnected by hyperlinks, which are typically activated by a mouse click, keypress sequence or by touching the screen. Apart from text, the hypertext is also sometimes used to describe tables, images. Hypertext is one of the key underlying concepts of the World Wide Web, as implemented on the Web, hypertext enables the easy-to-use publication of information over the Internet. The English prefix hyper- comes from the Greek prefix ὑπερ- and means over or beyond and it signifies the overcoming of the previous linear constraints of written text. The term hypertext is often used where the term hypermedia might seem appropriate, instead they use the strange term interactive multimedia, this is four syllables longer, and does not express the idea of extending hypertext. Hypertext documents can either be static or dynamic, static hypertext can be used to cross-reference collections of data in documents, software applications, or books on CDs. A well-constructed system can also incorporate other user-interface conventions, such as menus, links used in a hypertext document usually replace the current piece of hypertext with the destination document. A lesser known feature is StretchText, which expands or contracts the content in place, Hypertext can be used to support very complex and dynamic systems of linking and cross-referencing. The most famous implementation of hypertext is the World Wide Web, written in the months of 1990. In 1941, Jorge Luis Borges published The Garden of Forking Paths, in 1945, Vannevar Bush wrote an article in The Atlantic Monthly called As We May Think, about a futuristic proto-hypertext device he called a Memex. The coded symbols would enable the Memex to index, search, in 1963, Ted Nelson coined the terms hypertext and hypermedia as part of a model he developed for creating and using linked content. He later worked with Andries van Dam to develop the Hypertext Editing System in 1967 at Brown University, in December of that year, Engelbart demonstrated a hypertext interface to the public for the first time, in what has come to be known as The Mother of All Demos. The first hypermedia application is considered to be the Aspen Movie Map. The Movie Map allowed users to choose which way they wished to drive in a virtual cityscape. In 1980, Tim Berners-Lee created ENQUIRE, an early hypertext database system somewhat like a wiki but without hypertext punctuation, which was not invented until 1987. The early 1980s also saw a number of experimental hyperediting functions in word processors and hypermedia programs, many of whose features, guide, the first significant hypertext system for personal computers, was developed by Peter J. Brown at UKC in 1982. Sponsored by the founder of IBM, Thomas J, in 1983, Ben Shneiderman at the University of Maryland Human - Computer Interaction Lab led a group that developed the HyperTies system that was commercialized by Cognetics Corporation. Hyperties was used to create the July 1988 issue of the Communications of the ACM as a hypertext document, in August 1987, Apple Computer released HyperCard for the Macintosh line at the MacWorld convention
Hypertext
–
Engineer
Vannevar Bush wrote "
As We May Think " in 1945 describing his conception of the
Memex, a machine that could implement what we now call hypertext. His aim was to help humanity achieve a
collective memory with such a machine and avoid the use of scientific discoveries for destruction and war
Hypertext
–
Douglas Engelbart in 2008, at the 40th anniversary celebrations of "
The Mother of All Demos " in San Francisco, a 90-minute 1968 presentation of the
NLS computer system which was a combination of hardware and software that demonstrated many hyper text ideas
Hypertext
–
Ted Nelson gives a presentation on
Project Xanadu, a theoretical hyper text model conceived in the 1960s whose first and incomplete implementation was first published in 1998
Hypertext
–
Hypertext Editing System (HES)
IBM 2250 Display console – Brown University 1969
37.
WorldWideWeb
–
WorldWideWeb was the first web browser and editor. At the time it was written, it was the web browser in existence. The source code was released into the domain on April 30,1993. Some of the code still resides on Tim Berners-Lees NeXT Computer in the CERN museum and has not been recovered due to the status as a historical artifact. Berners-Lee wrote what would become known as WorldWideWeb on a NeXT Computer during the half of 1990. The first successful build was completed by December 25,1990, successive builds circulated among Berners-Lees colleagues at CERN before being released to the public, by way of Internet newsgroups, in August 1991. By this time, several others, including Bernd Pollermann, Robert Cailliau, Jean-François Groff, Berners-Lee proposed different names for his new application, The Mine of Information and The Information Mesh were proposals. At the end WorldWideWeb was chosen, but later renamed to Nexus to avoid confusion between the World Wide Web and the web browser. The team created so called passive browsers which do not have the ability to edit because it was hard to port this feature from the NeXT system to operating systems. A number of early browsers appeared, notably ViolaWWW and they were all eclipsed by Mosaic in terms of popularity, which by 1993 had replaced the WorldWideWeb program. Those involved in its creation had moved on to other tasks, such as defining standards, on April 30,1993, the CERN directorate released the source code of WorldWideWeb into the public domain. Several versions of the software are available on the web. Berners-Lee initially considered releasing it under the GNU General Public License, since WorldWideWeb was developed on and for the NeXTSTEP platform, the program uses many of NeXTSTEPs components – WorldWideWebs layout engine was built around NeXTSTEPs Text class. WorldWideWeb is capable of displaying basic style sheets, downloading and opening any file supported by the NeXT system, browsing newsgroups. In earlier versions, images are displayed in windows, until NeXTSTEPs Text class gained support for Image objects. WorldWideWeb is able to use different protocols, FTP, HTTP, NNTP, later versions are able to display inline images. The browser is also a WYSIWYG editor and it allows the simultaneous editing and linking of many pages in different windows. The functions Mark Selection, which creates an anchor, and Link to Marked, editing pages remotely is not possible, as the HTTP PUT method had not yet been implemented during the period of the applications active development
WorldWideWeb
–
WorldWideWeb, c. 1993
38.
CERN httpd
–
CERN httpd was a web server daemon originally developed at CERN from 1990 onwards by Tim Berners-Lee, Ari Luotonen and Henrik Frystyk Nielsen. Implemented in C, it was the first ever web server software and it could also be configured as a web proxy server. Version 0.1 was released in June 1991, in August 1991, Berners-Lee announced in the Usenet newsgroup alt. hypertext the availability of the source code of the server daemon and other World Wide Web software from the CERN FTP site. The server was presented on the Hypertext 91 conference in San Antonio and was part of the CERN Program Library, later versions of the server are based on the libwww library. The development of CERN httpd was later taken over by W3C, from 1996 onwards, W3C focused on the development of the Java-based Jigsaw server. The initial version was public domain software, the last one was under an MIT license
CERN httpd
–
This
NeXT Computer used by
Tim Berners-Lee at CERN became the world's first web server
39.
NeXTSTEP
–
NeXTSTEP is a discontinued object-oriented, multitasking operating system based on UNIX. Although relatively unsuccessful at the time, it attracted interest from computer scientists and it was also the platform on which Tim Berners-Lee created the first web browser. After the purchase of NeXT by Apple, it became the source of the operating systems macOS, iOS, watchOS and tvOS. Many bundled macOS applications, such as TextEdit, Mail and Chess, are descendants of NeXTSTEP applications, the toolkits offer considerable power, and are the canonical development system for all of the software on the machine. NeXTSTEPs user interface is considered to be refined and consistent and it introduced the idea of the Dock and the Shelf. Additional kits were added to the line to make the system more attractive. These include Portable Distributed Objects, which allow easy remote invocation, and Enterprise Objects Framework, the kits made the system particularly interesting to custom application programmers, and NeXTSTEP had a long history in the financial programming community. A preview release of NeXTSTEP was shown with the launch of the NeXT Computer on October 12,1988, the first full release, NeXTSTEP1.0, shipped on September 18,1989. NeXTSTEP was later modified to separate the underlying operating system from the higher-level object libraries, the result was the OpenStep API, which ran on multiple underlying operating systems, including NeXTs own OPENSTEP, Windows NT and SUN Solaris. NeXTSTEPs legacy stands today in the form of its direct descendents, from day one, the operating system of NeXTSTEP was built upon Mach/BSD. It was built on 4. 3BSD Tahoe and it changed to 4. 3BSD Reno after the release of NeXTSTEP3.0. It changed to 4. 4BSD during the development of Rhapsody, the first web browser, WorldWideWeb, and the first ever app store were all invented on the NeXTSTEP platform. Some features and keyboard shortcuts now commonly found in web browsers can be traced back to NeXTSTEP conventions, the basic layout options of HTML1.0 and 2.0 are attributable to those features available in NeXTs Text class. Other games based on the Doom engine such as Heretic and its sequel Hexen by Raven Software as well as Strife by Rogue Entertainment were also developed on NeXT hardware using ids tools. Altsys made a NeXTSTEP application called Virtuoso, version 2 of which was ported to Mac OS, the modern Notebook interface for Mathematica, and the advanced spreadsheet Lotus Improv, were developed using NeXTSTEP. The software that controlled MCIs Friends and Family calling plan program was developed using NeXTSTEP, about the time of the release of NeXTSTEP3.2, NeXT partnered with Sun Microsystems to develop OpenStep. It is the product of an effort to separate the underlying operating system from the higher-level object libraries to create a cross-platform object-oriented API standard derived from NeXTSTEP, the OpenStep API targets multiple underlying operating systems, including NeXTs own OPENSTEP. Implementations of that standard were released for Suns Solaris, Windows NT, NeXTs implementation is called OPENSTEP for Mach and its first release superseded NeXTSTEP3.3 on NeXT, Sun and Intel IA-32 systems
NeXTSTEP
–
NeXTSTEP
graphical user interface
40.
World Wide Web Consortium
–
The World Wide Web Consortium is the main international standards organization for the World Wide Web. As of 1 April 2017, the World Wide Web Consortium has 461 members, the W3C also engages in education and outreach, develops software and serves as an open forum for discussion about the Web. The World Wide Web Consortium was founded by Tim Berners-Lee after he left the European Organization for Nuclear Research in October,1994, the organization tries to foster compatibility and agreement among industry members in the adoption of new standards defined by the W3C. Incompatible versions of HTML are offered by different vendors, causing inconsistency in how web pages are displayed, the consortium tries to get all those vendors to implement a set of core principles and components which are chosen by the consortium. It was originally intended that CERN host the European branch of W3C, however, CERN wished to focus on particle physics, not information technology. In April 1995, the French Institute for Research in Computer Science and Automation became the European host of W3C, starting in 1997, W3C created regional offices around the world. In October 2012, W3C convened a community of major web players and publishers to establish a MediaWiki wiki that seeks to document open web standards called the WebPlatform and WebPlatform Docs. Sometimes, when a specification becomes too large, it is split into independent modules which can mature at their own pace, subsequent editions of a module or specification are known as levels and are denoted by the first integer in the title. Subsequent revisions on each level are denoted by a following an decimal point. The W3C standard formation process is defined within the W3C process document, after enough content has been gathered from editor drafts and discussion, it may be published as a working draft for review by the community. A WD document is the first form of a standard that is publicly available, commentary by virtually anyone is accepted, though no promises are made with regard to action on any particular element commented upon. At this stage, the document may have significant differences from its final form. As such, anyone who implements WD standards should be ready to significantly modify their implementations as the standard matures, a candidate recommendation is a version of a standard that is more mature than the WD. At this point, the responsible for the standard is satisfied that the standard meets its goal. The purpose of the CR is to aid from the development community as to how implementable the standard is. The standard document may change further, but at this point, significant features are mostly decided, the design of those features can still change due to feedback from implementors. A proposed recommendation is the version of a standard that has passed the two levels. The users of the standard provide input, at this stage, the document is submitted to the W3C Advisory Council for final approval
World Wide Web Consortium
–
World Wide Web Consortium
41.
Uniform Resource Locator
–
A Uniform Resource Locator, commonly informally termed a web address is a reference to a web resource that specifies its location on a computer network and a mechanism for retrieving it. A URL is a type of Uniform Resource Identifier, although many people use the two terms interchangeably. A URL implies the means to access a resource and is denoted by a protocol or an access mechanism. Thus http, //www. example. com is an URL, URLs occur most commonly to reference web pages, but are also used for file transfer, email, database access, and many other applications. Most web browsers display the URL of a web page above the page in an address bar, a typical URL could have the form http, //www. example. com/index. html, which indicates a protocol, a hostname, and a file name. The format combines the pre-existing system of names with file path syntax. Conventions already existed where server names could be prefixed to complete file paths, every HTTP URL conforms to the syntax of a generic URI. Although schemes are case-insensitive, the form is lowercase and documents that specify schemes must do so with lowercase letters. It is followed by a colon, examples of popular schemes include http, ftp, mailto, file, data, and irc. URI schemes should be registered with the Internet Assigned Numbers Authority, two slashes, This is required by some schemes and not required by some others. When the authority component is absent, the path component cannot begin with two slashes, iPv4 addresses must be in dot-decimal notation, and IPv6 addresses must be enclosed in brackets. An optional port number, separated from the hostname by a colon A path, which contains data, usually organized in hierarchical form, such a sequence may resemble or map exactly to a file system path, but does not always imply a relation to one. The path must begin with a single slash if an authority part was present, and may also if one was not, but must not begin with a double slash. The path is defined, though the defined path may be empty An optional query, separated from the preceding part by a question mark. Its syntax is not well defined, but by convention is most often a sequence of attribute–value pairs separated by a delimiter, an optional fragment, separated from the preceding part by a hash. The fragment contains a fragment identifier providing direction to a secondary resource, when the primary resource is an HTML document, the fragment is often an id attribute of a specific element, and web browsers will scroll this element into view. A web browser will usually dereference a URL by performing an HTTP request to the specified host, URLs using the https scheme require that requests and responses will be made over a secure connection to the website. Internet users are distributed throughout the world using a variety of languages and alphabets
Uniform Resource Locator
–
This
Euler diagram shows that a Uniform Resource Identifier (URI) is either a Uniform Resource Locator (URL), a
Uniform Resource Name (URN), or both.
42.
File system
–
In computing, a file system or filesystem is used to control how data is stored and retrieved. Without a file system, information placed in a storage medium would be one large body of data with no way to tell where one piece of information stops, by separating the data into pieces and giving each piece a name, the information is easily isolated and identified. Taking its name from the way paper-based information systems are named, the structure and logic rules used to manage the groups of information and their names is called a file system. There are many different kinds of file systems, each one has different structure and logic, properties of speed, flexibility, security, size and more. Some file systems have been designed to be used for specific applications, for example, the ISO9660 file system is designed specifically for optical discs. File systems can be used on different types of storage devices that use different kinds of media. The most common device in use today is a hard disk drive. Other kinds of media that are used include flash memory, magnetic tapes, in some cases, such as with tmpfs, the computers main memory is used to create a temporary file system for short-term use. Some file systems are used on local storage devices, others provide file access via a network protocol. Some file systems are virtual, meaning that the files are computed on request or are merely a mapping into a different file system used as a backing store. The file system access to both the content of files and the metadata about those files. It is responsible for arranging storage space, reliability, efficiency, before the advent of computers the term file system was used to describe a method of storing and retrieving paper documents. By 1961 the term was being applied to computerized filing alongside the original meaning, by 1964 it was in general use. A file system consists of two or three layers, sometimes the layers are explicitly separated, and sometimes the functions are combined. The logical file system is responsible for interaction with the user application and it provides the application program interface for file operations — OPEN, CLOSE, READ, etc. and passes the requested operation to the layer below it for processing. The logical file system manage open file table entries and per-process file descriptors and this layer provides file access, directory operations, security and protection. The second optional layer is the file system. This interface allows support for multiple concurrent instances of physical file systems, the third layer is the physical file system
File system
–
Directory listing in a
Windows command shell
43.
Apache server
–
The Apache HTTP Server, colloquially called Apache, is the worlds most used web server software. Originally based on the NCSA HTTPd server, development of Apache began in early 1995 after work on the NCSA code stalled. Apache played a key role in the growth of the World Wide Web, quickly overtaking NCSA HTTPd as the dominant HTTP server. In 2009, it became the first web server software to more than 100 million websites. Apache is developed and maintained by a community of developers under the auspices of the Apache Software Foundation. Most commonly used on a Unix-like system, the software is available for a variety of operating systems besides Unix, version 2.0 improved support for non-Unix, e. g. Windows and OS/2. Old versions of Apache were ported to run on e. g. OpenVMS, released under the Apache License, Apache is free and open-source software. As of July 2016, Apache was estimated to serve 46. 41% of all websites and 43. 18% of the top million websites. According to the FAQ in the Apache project website, the name Apache was chosen out of respect to the Native American tribe Apache and their skills in warfare. The name was believed to be a pun on A Patchy Server. I wish I could say that it was something fantastic, I put it on a page and then a few months later when this project started, I pointed people to this page and said, Hey, what do you think of that idea. Someone said they liked the name and that it was a good pun. He said, Well, were building a server out of a bunch of software patches, so its a patchy Web server. When I thought of the name, no and it just sort of connotated, Take no prisoners. Be kind of aggressive and kick some ass, when Apache is running, its process name is sometimes httpd, which is short for HTTP daemon. Apache supports a variety of features, many implemented as compiled modules which extend the core functionality and these can range from server-side programming language support to authentication schemes. Some common language interfaces support Perl, Python, Tcl, popular authentication modules include mod_access, mod_auth, mod_digest, and mod_auth_digest, the successor to mod_digest. A sample of other features include Secure Sockets Layer and Transport Layer Security support, a module, a URL rewriting module, custom log files
Apache server
–
Apache HTTP Server
44.
Unix
–
Among these is Apples macOS, which is the Unix version with the largest installed base as of 2014. Many Unix-like operating systems have arisen over the years, of which Linux is the most popular, Unix was originally meant to be a convenient platform for programmers developing software to be run on it and on other systems, rather than for non-programmer users. The system grew larger as the system started spreading in academic circles, as users added their own tools to the system. Unix was designed to be portable, multi-tasking and multi-user in a time-sharing configuration and these concepts are collectively known as the Unix philosophy. By the early 1980s users began seeing Unix as a universal operating system. Under Unix, the system consists of many utilities along with the master control program. To mediate such access, the kernel has special rights, reflected in the division between user space and kernel space, the microkernel concept was introduced in an effort to reverse the trend towards larger kernels and return to a system in which most tasks were completed by smaller utilities. In an era when a standard computer consisted of a disk for storage and a data terminal for input and output. However, modern systems include networking and other new devices, as graphical user interfaces developed, the file model proved inadequate to the task of handling asynchronous events such as those generated by a mouse. In the 1980s, non-blocking I/O and the set of inter-process communication mechanisms were augmented with Unix domain sockets, shared memory, message queues, and semaphores. In microkernel implementations, functions such as network protocols could be moved out of the kernel, Multics introduced many innovations, but had many problems. Frustrated by the size and complexity of Multics but not by the aims and their last researchers to leave Multics, Ken Thompson, Dennis Ritchie, M. D. McIlroy, and J. F. Ossanna, decided to redo the work on a much smaller scale. The name Unics, a pun on Multics, was suggested for the project in 1970. Peter H. Salus credits Peter Neumann with the pun, while Brian Kernighan claims the coining for himself, in 1972, Unix was rewritten in the C programming language. Bell Labs produced several versions of Unix that are referred to as Research Unix. In 1975, the first source license for UNIX was sold to faculty at the University of Illinois Department of Computer Science, UIUC graduate student Greg Chesson was instrumental in negotiating the terms of this license. During the late 1970s and early 1980s, the influence of Unix in academic circles led to adoption of Unix by commercial startups, including Sequent, HP-UX, Solaris, AIX. In the late 1980s, AT&T Unix System Laboratories and Sun Microsystems developed System V Release 4, in the 1990s, Unix-like systems grew in popularity as Linux and BSD distributions were developed through collaboration by a worldwide network of programmers
Unix
–
Ken Thompson (sitting) and
Dennis Ritchie working together at a
PDP-11
Unix
–
Evolution of Unix and Unix-like systems
Unix
–
Ken Thompson and
Dennis Ritchie, principal developers of
Research Unix
Unix
–
Photo from
USENIX 1984, including
Dennis Ritchie (center)
45.
Computer file
–
A computer file is a computer resource for recording data discretely in a computer storage device. Just as words can be written to paper, so can information be written to a computer file, there are different types of computer files, designed for different purposes. A file may be designed to store a picture, a message, a video. Some types of files can store different several types of information at once, by using computer programs, a person can open, read, change, and close a computer file. Computer files may be reopened, modified, and copied a number of times. Typically, computer files are organised in a system, which keeps track of where the files are. The word file derives from the Latin filum, such a file now exists in a memory tube developed at RCA Laboratories. Electronically it retains figures fed into calculating machines, holds them in storage while it memorizes new ones - speeds intelligent solutions through mazes of mathematics, in 1952, file denoted, inter alia, information stored on punched cards. In early use, the hardware, rather than the contents stored on it, was denominated a file. For example, the IBM350 disk drives were denominated disk files, although the contemporary register file demonstrates the early concept of files, its use has greatly decreased. On most modern operating systems, files are organized into one-dimensional arrays of bytes, for example, the bytes of a plain text file are associated with either ASCII or UTF-8 characters, while the bytes of image, video, and audio files are interpreted otherwise. Most file types also allocate a few bytes for metadata, which allows a file to some basic information about itself. Some file systems can store arbitrary file-specific data outside of the file format, on other file systems this can be done via sidecar files or software-specific databases. All those methods, however, are susceptible to loss of metadata than are container. At any instant in time, a file might have a size, normally expressed as number of bytes, in most modern operating systems the size can be any non-negative whole number of bytes up to a system limit. Many older operating systems kept track only of the number of blocks or tracks occupied by a file on a storage device. In such systems, software employed other methods to track the exact byte count, the general definition of a file does not require that its size have any real meaning, however, unless the data within the file happens to correspond to data within a pool of persistent storage. A special case is a zero byte file, these files can be newly created files that have not yet had any data written to them, or may serve as some kind of flag in the file system, or are accidents
Computer file
–
A
punched card file
Computer file
–
The twin
disk files of an
IBM 305 system
46.
Kernel (computing)
–
The kernel is a computer program that is the core of a computers operating system, with complete control over everything in the system. It is the first program loaded on start-up and it handles the rest of start-up as well as input/output requests from software, translating them into data-processing instructions for the central processing unit. It handles memory and peripherals like keyboards, monitors, printers, the critical code of the kernel is usually loaded into a protected area of memory, which prevents it from being overwritten by applications or other, more minor parts of the operating system. The kernel performs its tasks, such as running processes and handling interrupts, in contrast, everything a user does is in user space, writing text in a text editor, running programs in a GUI, etc. This separation prevents user data and kernel data from interfering with other and causing instability. The kernels interface is an abstraction layer. When a process makes requests of the kernel, it is called a system call, Kernel designs differ in how they manage these system calls and resources. A monolithic kernel runs all the operating instructions in the same address space. A microkernel runs most processes in space, for modularity. The kernel takes responsibility for deciding at any time which of the running programs should be allocated to the processor or processors. Random-access memory Random-access memory is used to both program instructions and data. Typically, both need to be present in memory in order for a program to execute, often multiple programs will want access to memory, frequently demanding more memory than the computer has available. The kernel is responsible for deciding which memory each process can use, input/output devices I/O devices include such peripherals as keyboards, mice, disk drives, printers, network adapters, and display devices. The kernel allocates requests from applications to perform I/O to an appropriate device, key aspects necessary in resource management are the definition of an execution domain and the protection mechanism used to mediate the accesses to the resources within a domain. Kernels also usually provide methods for synchronization and communication between processes called inter-process communication, finally, a kernel must provide running programs with a method to make requests to access these facilities. The kernel has full access to the memory and must allow processes to safely access this memory as they require it. Often the first step in doing this is virtual addressing, usually achieved by paging and/or segmentation, virtual addressing allows the kernel to make a given physical address appear to be another address, the virtual address. This allows every program to behave as if it is the one running
Kernel (computing)
–
A kernel connects the
application software to the hardware of a computer
47.
User-mode
–
In computer science, hierarchical protection domains, often called protection rings, are mechanisms to protect data and functionality from faults and malicious behaviour. This approach is diametrically opposite to that of capability-based security, computer operating systems provide different levels of access to resources. A protection ring is one of two or more levels or layers of privilege within the architecture of a computer system. This is generally hardware-enforced by some CPU architectures that provide different CPU modes at the hardware or microcode level, rings are arranged in a hierarchy from most privileged to least privileged. On most operating systems, Ring 0 is the level with the most privileges and interacts most directly with the hardware such as the CPU. Special gates between rings are provided to allow an outer ring to access an inner rings resources in a predefined manner, correctly gating access between rings can improve security by preventing programs from one ring or privilege level from misusing resources intended for programs in another. Programs such as web browsers running in higher numbered rings must request access to the network, multiple rings of protection were among the most revolutionary concepts introduced by the Multics operating system, a highly secure predecessor of todays Unix family of operating systems. However, most general-purpose systems use only two rings, even if the hardware they run on provides more CPU modes than that, many modern CPU architectures include some form of ring protection, although the Windows NT operating system, like Unix, does not fully utilize this feature. OS/2 did to some extent, using three rings, ring 0 for kernel code and device drivers, ring 2 for privileged code, under DOS, the kernel, drivers and applications typically run on ring 3, whereas 386 memory managers such as EMM386 run at ring 0. In addition to this, DR-DOS EMM3863. xx can optionally run some modules on ring 1 instead, openVMS uses four modes called Kernel, Executive, Supervisor and User. The original Multics system had eight rings, but many systems have fewer. The hardware remains aware of the current ring of the executing instruction thread at all times, in some systems, areas of virtual memory are instead assigned ring numbers in hardware. One example is the Data General Eclipse MV/8000, in which the top three bits of the program served as the ring register. The hardware severely restricts the ways in which control can be passed from one ring to another, the hardware restrictions are designed to limit opportunities for accidental or malicious breaches of security. In addition, the most privileged ring may be given special capabilities, the ARM v7 architecture implements three privilege levels, application, operating system, and hypervisor. Unusually, level 0 is the level, while level 2 is the most-privileged level. Ring protection can be combined with processor modes in some systems, operating systems running on hardware supporting both may use both forms of protection or only one. Effective use of ring architecture requires close cooperation between hardware and the operating system, operating systems designed to work on multiple hardware platforms may make only limited use of rings if they are not present on every supported platform
User-mode
–
Privilege rings for the
x86 available in
protected mode
48.
IP address
–
An IP address is an identifier assigned to each computer and other device connected to a TCP/IP network that is used to locate and identify the node in communications with other nodes on the network. IP addresses are written and displayed in human-readable notations, such as 172.16.254.1 in IPv4. Version 4 of the Internet Protocol defines an IP address as a 32-bit number and its deployment commenced in the mid-2000s and is ongoing. Addresses have been distributed by IANA to the RIRs in blocks of approximately 16.8 million addresses each, each ISP or private network administrator assigns an IP address to each device connected to its network. Such assignments may be on a static or dynamic basis, depending on its software, an IP address serves two principal functions, host or network interface identification and location addressing. Its role has been characterized as follows, A name indicates what we seek, an address indicates where it is. A route indicates how to get there, the header of each IP packet sent over the Internet must contain the IP address of both the destination server or website and of the sender. The Domain Name System translates domain names to the corresponding destination IP address, both the source address and the destination address may be changed in transit by a network address translation device. The senders IP address is available to the server and becomes the destination address when the server responds to a client request. A sender wanting to remain anonymous to the server may use a proxy server, when the destination server responds to the proxy server, it would forward it on to the true client—ie. Change the IP address to that of the originator of the request, a reverse DNS lookup involves the querying of DNS to determine the domain name associated with an IP address. There are two versions of the Internet Protocol, IP version 4 and IP version 6, each version defines an IP address differently. Because of its prevalence, the generic term IP address typically still refers to the addresses defined by IPv4. The gap in version sequence between IPv4 and IPv6 resulted from the assignment of number 5 to the experimental Internet Stream Protocol in 1979, an IP address in IPv4 is 32-bits in size, which limits the address space to 4294967296 IP addresses. Of this number, IPv4 reserves some addresses for special purposes such as private networks or multicast addresses. IPv4 addresses are usually represented in dot-decimal notation, consisting of four numbers, each ranging from 0 to 255, separated by dots. Each part represents a group of 8 bits of the address, in some cases of technical writing, IPv4 addresses may be presented in various hexadecimal, octal, or binary representations. In the early stages of development of the Internet Protocol, network administrators interpreted an IP address in two parts, network number portion and host number portion
IP address
–
Decomposition of an IPv4 address from
dot-decimal notation to its binary value.
49.
Personal computer hardware
–
Computer hardware is the collection of physical components that constitute a computer system. By contrast, software is instructions that can be stored and run by hardware, hardware is directed by the software to execute any command or instruction. A combination of hardware and software forms a usable computing system, the template for all modern computers is the Von Neumann architecture, detailed in a 1945 paper by Hungarian mathematician John von Neumann. The meaning of the term has evolved to mean a stored-program computer in which an instruction fetch and this is referred to as the Von Neumann bottleneck and often limits the performance of the system. For the third year, U. S. business-to-business channel sales increased. The impressive growth was the fastest sales increase since the end of the recession, sales growth accelerated in the second half of the year peaking in fourth quarter with a 6.9 percent increase over the fourth quarter of 2012. There are a number of different types of system in use today. The personal computer, also known as the PC, is one of the most common types of computer due to its versatility, laptops are generally very similar, although they may use lower-power or reduced size components, thus lower performance. The computer case is a plastic or metal enclosure that houses most of the components, a case can be either big or small, but the form factor of motherboard for which it is designed matters more. A power supply unit converts alternating current electric power to low-voltage DC power for the components of the computer. Laptops are capable of running from a battery, normally for a period of hours. The motherboard is the component of a computer. It is usually cooled by a heatsink and fan, or water-cooling system, most newer CPUs include an on-die Graphics Processing Unit. The clock speed of CPUs governs how fast it executes instructions, many modern computers have the option to overclock the CPU which enhances performance at the expense of greater thermal output and thus a need for improved cooling. The chipset, which includes the bridge, mediates communication between the CPU and the other components of the system, including main memory. Random-Access Memory, which stores the code and data that are being accessed by the CPU. For example, when a web browser is opened on the computer it takes up memory, RAM usually comes on DIMMs in the sizes 2GB, 4GB, and 8GB, but can be much larger. Read-Only Memory, which stores the BIOS that runs when the computer is powered on or otherwise begins execution, the BIOS includes boot firmware and power management firmware
Personal computer hardware
–
PDP-11 CPU board.
Personal computer hardware
–
Inside a custom-built computer: power supply at the bottom has its own cooling fan.
Personal computer hardware
–
An
IBM System z9 mainframe.
.svg)
