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. Files can be transferred through the internet. There are different types of computer files, designed for different purposes. A file may be designed to store a picture, a written message, a video, a computer program, or a wide variety of other kinds of data; some types of files can store several types of information at once. By using computer programs, a person can open, change and close a computer file. Computer files may be reopened and copied an arbitrary number of times. Files are organised in a file system, which keeps track of where the files are located on disk and enables user access; the word "file" derives from the Latin filum."File" was used in the context of computer storage as early as January 1940. In Punched Card Methods in Scientific Computation, W. J. Eckert stated, "The first extensive use of the early Hollerith Tabulator in astronomy was made by Comrie.
He used it for building a table from successive differences, for adding large numbers of harmonic terms". "Tables of functions are constructed from their differences with great efficiency, either as printed tables or as a file of punched cards." In February 1950: In a Radio Corporation of America advertisement in Popular Science Magazine describing a new "memory" vacuum tube it had developed, RCA stated: "the results of countless computations can be kept'on file' and taken out again. 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, information stored on punched cards. In early use, the underlying hardware, rather than the contents stored on it, was denominated a "file". For example, the IBM 350 disk drives were denominated "disk files"; the introduction, circa 1961, by the Burroughs MCP and the MIT Compatible Time-Sharing System of the concept of a "file system" that managed several virtual "files" on one storage device is the origin of the contemporary denotation of the word.
Although the contemporary "register file" demonstrates the early concept of files, its use has decreased. On most modern operating systems, files are organized into one-dimensional arrays of bytes; the format of a file is defined by its content since a file is a container for data, although, on some platforms the format is indicated by its filename extension, specifying the rules for how the bytes must be organized and interpreted meaningfully. For example, the bytes of a plain text file are associated with either ASCII or UTF-8 characters, while the bytes of image and audio files are interpreted otherwise. Most file types allocate a few bytes for metadata, which allows a file to carry some basic information about itself; some file systems can store arbitrary file-specific data outside of the file format, but linked to the file, for example extended attributes or forks. On other file systems this can be done via software-specific databases. All those methods, are more susceptible to loss of metadata than are container and archive file formats.
At any instant in time, a file might have a size expressed as number of bytes, that indicates how much storage is associated with the file. 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 physical 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, 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. For example, the file to which the link /bin/ls points in a typical Unix-like system has a defined size that changes. Compare this with /dev/null, a file, but its size may be obscure. Information in a computer file can consist of smaller packets of information that are individually different but share some common traits. For example, a payroll file might contain information concerning all the employees in a company and their payroll details.
A text file may contain lines of corresponding to printed lines on a piece of paper. Alternatively, a file may contain an arbitrary binary image or it may contain an executable; the way information is grouped into a file is up to how it is designed. This has led to a plethora of more or less standardized file structures for all imaginable purposes, from the simplest to the most complex. Most computer files are used by computer programs which create, modify or delete the files for their own use on an as-needed basis; the programmers who create the programs decide what files are needed, how they are to be used and their names. In some cases, computer pr
XWD, an acronym for Cross-Wheel Drive, is an advanced all-wheel drive system designed by Haldex in partnership with Saab. Known as Haldex Generation 4, it is an intelligent permanent all-wheel drive system that can pre-emptively and continuously change torque distribution before wheel slip occurs. To achieve optimum take-off performance, Saab XWD is capable of locking the front and rear axles, but can adapt as little as 4% of torque to the rear wheels during highway cruising, thus maximizing fuel economy. To ensure immediate traction, torque distribution can be transferred to the wheel with the most grip in fractions of a second, using the two couplings the XWD system can send 85% of available torque to a single rear wheel; the ability to transfer torque laterally between the rear wheels is similar to Mitsubishi's Super Active Yaw Control. An ECU continuously collects various data from the car's onboard systems, in conjunction with the ESC, ABS and TCS calculates the best torque distribution in the driveline.
The XWD system debuted on the 2008 limited edition Saab Turbo X, equipped with an electronically controlled limited slip differential and was made available through the rest of the 9-3 line. XWD was to be the standard drivetrain for the 2010-2012 Saab 9-5, would have underpinned Saab's upcoming cross-over utility vehicle, the 2011 Saab 9-4X, if it had reached production, as well as the Saab 9-3X, an XUV version of the 9-3 SportCombi; the XWD system is used in the Opel Insignia. While the Haldex Generation 4 system will be made available to other automobile manufacturers starting 2009, the XWD moniker was a trademark owned by Saab Automobile AB, thus cannot be used by any other make; as of the bankruptcy of Saab Automobile AB in 2011, the XWD name will no longer be used in any production vehicle
O'Reilly Media is an American media company established by Tim O'Reilly that publishes books and Web sites and produces conferences on computer technology topics. Their distinctive brand features a woodcut of an animal on many of their book covers; the company began in 1978 as a private consulting firm doing technical writing, based in the Cambridge, Massachusetts area. In 1984, it began to retain publishing rights on manuals created for Unix vendors. A few 70-page "Nutshell Handbooks" were well-received, but the focus remained on the consulting business until 1988. After a conference displaying O'Reilly's preliminary Xlib manuals attracted significant attention, the company began increasing production of manuals and books; the original cover art consisted of animal designs developed by Edie Freedman because she thought that Unix program names sounded like "weird animals". In 1993 O'Reilly Media created the first web portal, when they launched one of the first Web-based resources, Global Network Navigator.
GNN was sold to AOL in one of the first large transactions of the dot-com bubble. GNN was the first site on the World Wide Web to feature paid advertising. Although O'Reilly Media got its start in publishing two decades after its genesis the company expanded into event production. In 1997, O'Reilly launched The Perl Conference to cross-promote its books on the Perl programming language. Many of the company's other software bestsellers were on topics that were off the radar of the commercial software industry. In 1998, O'Reilly invited many of the leaders of software projects to a meeting. Called the freeware summit, the meeting became known as the Open Source Summit; the O'Reilly Open Source Convention is now one of O'Reilly's flagship events. Other key events include the Strata Conference on big data, the Velocity Conference on Web Performance and Operations, FOO Camp. Past events of note include the Web 2.0 Summit. Overall, O'Reilly describes its business not as publishing or conferences, but as "changing the world by spreading the knowledge of innovators."Today, the company offers over one dozen conferences: Strata + Hadoop World OSCON Fluent Velocity The Next:Economy Summit The Next:Money Summit The Solid Conference The O'Reilly Software Architecture Conference The O'Reilly Design Conference O'Reilly Emerging Technology Conference Tools of Change Conference Web 2.0 Summit Web 2.0 Expo MySQL Conference and Expo RailsConf Where 2.0 Money:Tech Gov 2.0 Expo and Gov 2.0 Summit O'Reilly school of technology will be discontinued as of January 6, 2016, new enrollments are no longer accepted.
In the late 1990s, O'Reilly founded the O'Reilly Network, which grew to include sites such as: LinuxDevCenter.com MacDevCenter.com WindowsDevCenter.com ONLamp.com O'Reilly RadarIn 2008 the company revised its online model and stopped publishing on several of its sites. The company produced dev2dev in association with BEA and java.net in association with Sun Microsystems and CollabNet. In 2001, O'Reilly launched Safari Books Online, a subscription-based service providing access to ebooks as a joint venture with the Pearson Technology Group. Safari Books Online includes books and video from Adobe Press, Alpha Books, Cisco Press, FT Press, Microsoft Press, New Riders Publishing, O'Reilly, Peachpit Press, Prentice Hall, Prentice Hall PTR, Que and Sams Publishing. In 2014, O'Reilly Media acquired Pearson's stake, making Safari Books Online a wholly owned subsidiary of O'Reilly Media. O'Reilly did a redesign of the site and has some success in the attempt to expand beyond Safari's core B2C market into the B2B Enterprise market.
In 2017, O'Reilly Media announced they were no longer selling books including eBooks. Instead, everyone was encouraged to sign up to Safari. In 2003, after the dot com bust, O'Reilly's corporate goal was to reignite enthusiasm in the computer industry. To do this, Dale Dougherty and Tim O'Reilly decided to use the term "Web 2.0" coined in January 1999 by Darcy DiNucci. The term was used for the Web 2.0 Summit run by O'Reilly TechWeb. CMP registered Web 2.0 as a Service Mark "for arranging and conducting live events, namely trade shows, business conferences and educational conferences in various fields of computers and information technology." Web 2.0 framed what distinguished the companies that survived the dot com bust from those that died, identified key drivers of future success, including what is now called “cloud computing,” big data, new approaches to iterative, data-driven software development. In May 2006 CMP Media learned of an impending event called the "Web 2.0 Half day conference."
Concerned over their obligation to take reasonable means to enforce their trade and service marks CMP sent a cease and desist letter to the non-profit Irish organizers of the event. This attempt to restrict through legal mechanisms the use of the term was criticized by some; the legal issue was resolved by O'Reilly's apologizing for the early and aggressive involvement of attorneys, rather than calling the organizers, allowing them to use the service mark for this single event. In January 2005 the compan
X Window System
The X Window System is a windowing system for bitmap displays, common on Unix-like operating systems. X provides the basic framework for a GUI environment: drawing and moving windows on the display device and interacting with a mouse and keyboard. X does not mandate the user interface – this is handled by individual programs; as such, the visual styling of X-based environments varies greatly. X originated at the Massachusetts Institute of Technology in 1984; the X protocol has been version 11 since September 1987. The X. Org Foundation leads the X project, with the current reference implementation, X. Org Server, available as free and open source software under the MIT License and similar permissive licenses. X is an architecture-independent system for remote graphical user interfaces and input device capabilities; each person using a networked terminal has the ability to interact with the display with any type of user input device. In its standard distribution it is a complete, albeit simple and interface solution which delivers a standard toolkit and protocol stack for building graphical user interfaces on most Unix-like operating systems and OpenVMS, has been ported to many other contemporary general purpose operating systems.
X provides the basic framework, or primitives, for building such GUI environments: drawing and moving windows on the display and interacting with a mouse, keyboard or touchscreen. X does not mandate the user interface. Programs may use X's graphical abilities with no user interface; as such, the visual styling of X-based environments varies greatly. Unlike most earlier display protocols, X was designed to be used over network connections rather than on an integral or attached display device. X features network transparency, which means an X program running on a computer somewhere on a network can display its user interface on an X server running on some other computer on the network; the X server is the provider of graphics resources and keyboard/mouse events to X clients, meaning that the X server is running on the computer in front of a human user, while the X client applications run anywhere on the network and communicate with the user's computer to request the rendering of graphics content and receive events from input devices including keyboards and mice.
The fact that the term "server" is applied to the software in front of the user is surprising to users accustomed to their programs being clients to services on remote computers. Here, rather than a remote database being the resource for a local app, the user's graphic display and input devices become resources made available by the local X server to both local and remotely hosted X client programs who need to share the user's graphics and input devices to communicate with the user. X's network protocol is based on X command primitives; this approach allows both 2D and 3D operations by an X client application which might be running on a different computer to still be accelerated on the X server's display. For example, in classic OpenGL, display lists containing large numbers of objects could be constructed and stored in the X server by a remote X client program, each rendered by sending a single glCallList across the network. X provides no native support for audio. X uses a client–server model: an X server communicates with various client programs.
The server sends back user input. The server may function as: an application displaying to a window of another display system a system program controlling the video output of a PC a dedicated piece of hardwareThis client–server terminology – the user's terminal being the server and the applications being the clients – confuses new X users, because the terms appear reversed, but X takes the perspective of the application, rather than that of the end-user: X provides display and I/O services to applications, so it is a server. The communication protocol between server and client operates network-transparently: the client and server may run on the same machine or on different ones with different architectures and operating systems. A client and server can communicate securely over the Internet by tunneling the connection over an encrypted network session. An X client itself may emulate an X server by providing display services to other clients; this is known as "X nesting". Open-source clients such as Xnest and Xephyr support such X nesting.
To use an X client application on a remote machine, the user may do the following: on the local machine, open a terminal window use ssh with the X forwarding argument to connect to the remote machine request local display/input service The remote X client application will make a connection to the user's local X server, providing display and input to the user. Alternatively, the local machine may run a small program that connects to the remote machine and starts the client application. Practical examples of remote clients include: administering a remote machine graphically using a client application to join with large numbers of other terminal users in collaborative workgroups running a computationally intensive simulation on a remote machine and displaying the results on
High color graphics is a method of storing image information in a computer's memory such that each pixel is represented by two bytes. The color is represented by all 16 bits, but some devices support 15-bit high color. More high color has been used by Microsoft to distinguish display systems that can make use of more than 8-bits per color channel from traditional 8-bit per color channel formats; this is a distinct usage from the 15-bit or 16-bit formats traditionally associated with the phrase high color. In 15-bit high color, one of the bits of the two bytes is ignored or set aside for an alpha channel, the remaining 15 bits are split between the red and blue components of the final color, like this: Each of the RGB components has 5 bits associated, giving 2⁵ = 32 intensities of each component; this allows 32768 possible colors for each pixel. The popular Cirrus Logic graphics chips of the early 1990s made use of the spare high-order bit for their so-called "mixed" video modes: with bit 15 clear, bits 0 through 14 would be treated as an RGB value as described above, while with bit 15 set, bit 0 through 7 would be interpreted as an 8-bit index into a 256-color palette This would have enabled display of high-quality color images side by side with palette-animated screen elements, but in practice, this feature was hardly used by any software.
When all 16 bits are used, one of the components gets an extra bit, allowing 64 levels of intensity for that component, a total of 65536 available colors. This can lead to small discrepancies in encoding, e.g. when one wishes to encode the 24-bit colour RGB with 16 bits. Forty in binary is 00101000; the red and blue channels will take the five most significant bits, will have a value of 00101, or 5 on a scale from 0 to 31. The green channel, with six bits of precision, will have a binary value of 001010, or 10 on a scale from 0 to 63; because of this, the colour RGB will have a slight purple tinge. Note that 40 on a scale from 0 to 255 is 15.7%. Green is chosen for the extra bit in 16 bits because the human eye has its highest sensitivity for green shades. For a demonstration, look at the following picture where dark shades of red and blue are shown using 128 levels of intensities for each component. Readers with normal vision should see the individual shades of green easily, while the shades of red should be difficult to see, the shades of blue are indistinguishable.
More some systems support having the extra bit of colour depth on the red or blue channel in applications where that colour is more prevalent. There is no need for a color look up table when in high color mode, because there are enough available colors per pixel to represent graphics and photos reasonably satisfactorily. However, the lack of precision decreases image fidelity. 24-bit color 30/36/48-bit color Color depth Planar Packed pixel List of monochrome and RGB palettes — 15-bit RGB and 16-bit RGB sections
International standards are technical standards developed by international standards organizations. International standards are available for use worldwide; the most prominent organization is the International Organization for Standardization. International standards may be used either by direct application or by a process of modifying an international standard to suit local conditions; the adoption of international standards results in the creation of equivalent, national standards that are the same as international standards in technical content, but may have editorial differences as to appearance, use of symbols and measurement units, substitution of a point for a comma as the decimal marker, differences resulting from conflicts in governmental regulations or industry-specific requirements caused by fundamental climatic, technological, or infrastructural factors, or the stringency of safety requirements that a given standard authority considers appropriate. International standards are one way of overcoming technical barriers in international commerce caused by differences among technical regulations and standards developed independently and separately by each nation, national standards organization, or company.
Technical barriers arise when different groups come together, each with a large user base, doing some well established thing that between them is mutually incompatible. Establishing international standards is one way of preventing or overcoming this problem; the implementation of standards in industry and commerce became important with the onset of the Industrial Revolution and the need for high-precision machine tools and interchangeable parts. Henry Maudslay developed the first industrially practical screw-cutting lathe in 1800, which allowed for the standardisation of screw thread sizes for the first time. Maudslay's work, as well as the contributions of other engineers, accomplished a modest amount of industry standardization. Joseph Whitworth's screw thread measurements were adopted as the first national standard by companies around the country in 1841, it came to be known as the British Standard Whitworth, was adopted in other countries. By the end of the 19th century differences in standards between companies were making trade difficult and strained.
The Engineering Standards Committee was established in London in 1901 as the world's first national standards body. After the First World War, similar national bodies were established in other countries; the Deutsches Institut für Normung was set up in Germany in 1917, followed by its counterparts, the American National Standard Institute and the French Commission Permanente de Standardisation, both in 1918. By the mid to late 19th century, efforts were being made to standardize electrical measurement. An important figure was R. E. B. Crompton, who became concerned by the large range of different standards and systems used by electrical engineering companies and scientists in the early 20th century. Many companies had entered the market in the 1890s and all chose their own settings for voltage, frequency and the symbols used on circuit diagrams. Adjacent buildings would have incompatible electrical systems because they had been fitted out by different companies. Crompton could see the lack of efficiency in this system and began to consider proposals for an international standard for electric engineering.
In 1904, Crompton represented Britain at the Louisiana Purchase Exposition in St. Louis as part of a delegation by the Institute of Electrical Engineers, he presented a paper on standardisation, so well received that he was asked to look into the formation of a commission to oversee the process. By 1906 his work was complete and he drew up a permanent constitution for the first international standards organization, the International Electrotechnical Commission; the body held its first meeting that year with representatives from 14 countries. In honour of his contribution to electrical standardisation, Lord Kelvin was elected as the body's first President; the International Federation of the National Standardizing Associations was founded in 1926 with a broader remit to enhance international cooperation for all technical standards and specifications. The body was suspended in 1942 during World War II. After the war, ISA was approached by the formed United Nations Standards Coordinating Committee with a proposal to form a new global standards body.
In October 1946, ISA and UNSCC delegates from 25 countries met in London and agreed to join forces to create the new International Organization for Standardization. List of international common standards List of technical standard organisations
Cursor (user interface)
In computer user interfaces, a cursor is an indicator used to show the current position for user interaction on a computer monitor or other display device that will respond to input from a text input or pointing device. The mouse cursor is called a pointer, owing to its resemblance in usage to a pointing stick. Cursor is Latin for'runner.' A cursor is the name given to the transparent slide engraved with a hairline, used for marking a point on a slide rule. The term was transferred to computers through analogy. In most command-line interfaces or text editors, the text cursor known as a caret, is an underscore, a solid rectangle, or a vertical line, which may be flashing or steady, indicating where text will be placed when entered. In text mode displays, it was not possible to show a vertical bar between characters to show where the new text would be inserted, so an underscore or block cursor was used instead. In situations where a block was used, the block was created by inverting the pixels of the character using the boolean math exclusive or function.
On text editors and word processors of modern design on bitmapped displays, the vertical bar is used instead. In a typical text editing application, the cursor can be moved by pressing various keys; these include the four arrow keys, the Page Up and Page Down keys, the Home key, the End key, various key combinations involving a modifier key such as the Control key. The position of the cursor may be changed by moving the mouse pointer to a different location in the document and clicking; the blinking of the text cursor is temporarily suspended when it is being moved. Some interfaces use an underscore or thin vertical bar to indicate that the user is in insert mode, a mode where text will be inserted in the middle of the existing text, a larger block to indicate that the user is in overtype mode, where inserted text will overwrite existing text. In this way, a block cursor may be seen as a piece of selected text one character wide, since typing will replace the text "in" the cursor with the new text.
A vertical line text cursor with a small left-pointing or right-pointing appendage are for indicating the direction of text flow on systems that support bi-directional text, is thus known among programmers as a'bidi cursor'. In some cases, the cursor may split into two parts, each indicating where left-to-right and right-to-left text would be inserted; the pointer or mouse cursor echoes movements of the pointing device a mouse, touchpad or trackball. This kind of cursor is used to manipulate elements of graphical user interfaces such as menus, scrollbars or any other widget, it may be called a "mouse pointer," because the mouse is the dominant type of pointing device used with desktop computers. The I-beam pointer is a cursor shaped like a serifed capital letter "I"; the purpose of this cursor is to indicate that the text beneath the cursor can be highlighted, sometimes inserted or changed. The idea of a cursor being used as a marker or insertion point for new data or transformations, such as rotation, can be extended to a 3D modeling environment.
Blender, for instance, uses a 3D cursor to determine. Susan Kare, designer of several of the common cursor shapes Creating and controlling browser cursors Cross-browser CSS custom cursors Installing A Cursor On Your Computer