Computing is any activity that uses computers. It includes developing hardware and software, using computers to manage and process information and entertain. Computing is a critically important, integral component of modern industrial technology. Major computing disciplines include computer engineering, software engineering, computer science, information systems, information technology; the ACM Computing Curricula 2005 defined "computing" as follows: "In a general way, we can define computing to mean any goal-oriented activity requiring, benefiting from, or creating computers. Thus, computing includes designing and building hardware and software systems for a wide range of purposes; the list is endless, the possibilities are vast." and it defines five sub-disciplines of the computing field: computer science, computer engineering, information systems, information technology, software engineering. However, Computing Curricula 2005 recognizes that the meaning of "computing" depends on the context: Computing has other meanings that are more specific, based on the context in which the term is used.
For example, an information systems specialist will view computing somewhat differently from a software engineer. Regardless of the context, doing computing well can be complicated and difficult; because society needs people to do computing well, we must think of computing not only as a profession but as a discipline. The term "computing" has sometimes been narrowly defined, as in a 1989 ACM report on Computing as a Discipline: The discipline of computing is the systematic study of algorithmic processes that describe and transform information: their theory, design, efficiency and application; the fundamental question underlying all computing is "What can be automated?" The term "computing" is synonymous with counting and calculating. In earlier times, it was used in reference to the action performed by mechanical computing machines, before that, to human computers; the history of computing is longer than the history of computing hardware and modern computing technology and includes the history of methods intended for pen and paper or for chalk and slate, with or without the aid of tables.
Computing is intimately tied to the representation of numbers. But long before abstractions like the number arose, there were mathematical concepts to serve the purposes of civilization; these concepts include one-to-one correspondence, comparison to a standard, the 3-4-5 right triangle. The earliest known tool for use in computation was the abacus, it was thought to have been invented in Babylon circa 2400 BC, its original style of usage was by lines drawn in sand with pebbles. Abaci, of a more modern design, are still used as calculation tools today; this was the first known calculation aid - preceding Greek methods by 2,000 years. The first recorded idea of using digital electronics for computing was the 1931 paper "The Use of Thyratrons for High Speed Automatic Counting of Physical Phenomena" by C. E. Wynn-Williams. Claude Shannon's 1938 paper "A Symbolic Analysis of Relay and Switching Circuits" introduced the idea of using electronics for Boolean algebraic operations. A computer is a machine that manipulates data according to a set of instructions called a computer program.
The program has an executable form. The same program in its human-readable source code form, enables a programmer to study and develop a sequence of steps known as an algorithm; because the instructions can be carried out in different types of computers, a single set of source instructions converts to machine instructions according to the central processing unit type. The execution process carries out the instructions in a computer program. Instructions express, they trigger sequences of simple actions on the executing machine. Those actions produce effects according to the semantics of the instructions. Computer software or just "software", is a collection of computer programs and related data that provides the instructions for telling a computer what to do and how to do it. Software refers to one or more computer programs and data held in the storage of the computer for some purposes. In other words, software is a set of programs, procedures and its documentation concerned with the operation of a data processing system.
Program software performs the function of the program it implements, either by directly providing instructions to the computer hardware or by serving as input to another piece of software. The term was coined to contrast with the old term hardware. In contrast to hardware, software is intangible. Software is sometimes used in a more narrow sense, meaning application software only. Application software known as an "application" or an "app", is a computer software designed to help the user to perform specific tasks. Examples include enterprise software, accounting software, office suites, graphics software and media players. Many application programs deal principally with documents. Apps may be published separately; some users need never install one. Application software is contrasted with system software and middleware, which manage and integrate a computer's capabilities, but
Desktop Window Manager
Desktop Window Manager is the window manager in Windows Vista, Windows 7, Windows 8 and Windows 10 that enables the use of hardware acceleration to render the graphical user interface of Windows. It was created to enable portions of the new "Windows Aero" user experience, which allowed for effects such as transparency, 3D window switching and more, it is included with Windows Server 2008, but requires the "Desktop Experience" feature and compatible graphics drivers to be installed. The Desktop Window Manager is a compositing window manager; this means. By comparison, the stacking window manager in Windows XP and earlier comprises a single display buffer to which all programs write. DWM works in different ways depending on the operating system and on the version of the graphics drivers it uses. Under Windows 7 and with WDDM 1.1 drivers, DWM only writes the program's buffer to the video RAM if it is a graphics device interface program. This is because Windows 7 supports hardware acceleration for GDI and in doing so does not need to keep a copy of the buffer in system RAM so that the CPU can write to it.
Because the compositor has access to the graphics of all applications, it allows visual effects that string together visuals from multiple applications, such as transparency. DWM uses DirectX 9 to perform the function of compositing and rendering in the GPU, freeing the CPU of the task of managing the rendering from the off-screen buffers to the display. However, it does not affect applications painting to the off-screen buffers – depending on the technologies used for that, this might still be CPU-bound. DWM-agnostic rendering techniques like GDI are redirected to the buffers by rendering the user interface as bitmaps. DWM-aware rendering technologies like WPF directly make the internal data structures available in a DWM-compatible format; the window contents in the buffers are converted to DirectX textures. The desktop itself is a full-screen Direct3D surface, with windows being represented as a mesh consisting of two adjacent triangles, which are transformed to represent a 2D rectangle; the texture, representing the UI chrome, is mapped onto these rectangles.
Window transitions are implemented as transformations of the meshes. With Windows Vista, the transitions are limited to the set of built-in shaders that implement the transformations. Greg Schechter, a developer at Microsoft has suggested that this might be opened up for developers and users to plug in their own effects in a future release. DWM only maps the primary desktop object as a 3D surface; because all applications render to an off-screen buffer, they can be read off the buffer embedded in other applications as well. Since the off-screen buffer is updated by the application, the embedded rendering will be a dynamic representation of the application window and not a static rendering; this is how the live thumbnail previews and Windows Flip work in Windows Vista and Windows 7. DWM exposes a public API; the size of the thumbnail is not fixed. Windows Flip 3D does not use the public thumbnail APIs as they do not allow for directly accessing the Direct3D textures. Instead, Flip 3D is implemented directly in the DWM engine.
The Desktop Window Manager uses Media Integration Layer, the unmanaged compositor which it shares with Windows Presentation Foundation, to represent the windows as composition nodes in a composition tree. The composition tree represents the desktop and all the windows hosted in it, which are rendered by MIL from the back of the scene to the front. Since all the windows contribute to the final image, the color of a resultant pixel can be decided by more than one window; this is used to implement effects such as per-pixel transparency. DWM allows custom shaders to be invoked to control how pixels from multiple applications are used to create the displayed pixel; the DWM includes built-in Pixel Shader 2.0 programs which compute the color of a pixel in a window by averaging the color of the pixel as determined by the window behind it and its neighboring pixels. These shaders are used by DWM to achieve the blur effect in the window borders of windows managed by DWM, optionally for the areas where it is requested by the application.
Since MIL provides a retained mode graphics system by caching the composition trees, the job of repainting and refreshing the screen when windows are moved is handled by DWM and MIL, freeing the application of the responsibility. The background data is in the composition tree and the off-screen buffers and is directly used to render the background. In pre-Vista Windows OSs, background applications had to be requested to re-render themselves by sending them the WM_PAINT message. DWM uses double-buffered graphics to prevent tearing when moving windows; the compositing engine uses optimizations such as culling to improve performance, as well as not redrawing areas that have not changed. Because the compositor is multi-monitor aware, DWM natively supports this too. During full-screen applications, such as games, DWM does not perform window compositing and therefore performance will not appreciably decrease. On Wind
Microsoft Gadgets are lightweight single-purpose applications, or software widgets, that can sit on a Microsoft Windows user's computer desktop, or are hosted on a web page. According to Microsoft, it will be possible for the different types of gadgets to run on different environments without modification, but this is not the case; the gadgets and the Windows desktop Sidebar were a hallmark feature in Windows Vista and Windows 7 editions of the operating system. Subsequently, Microsoft deemed them to be security vulnerabilities and discontinued developing and providing Microsoft Gadgets, which were no longer available by the time Windows 8 and 10 rolled out. Independent third party gadgets like Rainmeter continue to be developed and provided for versions of Windows. Microsoft gadgets can work on Windows XP Service Pack 3 but it needs Alky for Applications. Web gadgets - run on a web site, such as Bing.com or Spaces. Sidebar gadgets - run on the desktop or be docked onto, run on the Windows Sidebar.
SideShow gadgets - run on auxiliary external displays, such as on the outside of a laptop or on an LCD panel in a keyboard, mobile phones and other devices. Web gadgets run on Web sites such as Live.com and Windows Live Spaces Live.com lets users add RSS feeds in order to view news at a glance. Building off Microsoft's start.com experimental page, Live.com can be customized with Web Gadgets, mini-applications that can serve any purpose. Some gadgets integrate with other Windows Live services, including Mail and Favorites. Users can create multiple site tabs and customize each with different feeds, gadgets and color schemes. Desktop gadgets are desktop widgets, they can be used to control external applications such as Windows Media Center. A panel, or sidebar, is found on either the right side or the left side of the Windows desktop in the Windows Vista operating system. Gadgets can be placed on this sidebar, they are automatically aligned on it. Gadgets can be placed elsewhere on the screen, which causes them to expand and display more information.
In Windows 7, the sidebar is removed, although gadgets can somewhat be aligned on any side of the screen. Gadgets are toggled between the two sizes via a button in Windows 7. Windows SideShow is a new technology that lets Windows Vista drive small auxiliary displays of various form factors, offering bite-size pieces of information; these include displays embedded on the outside of a laptop lid or on a detachable device, enabling access to information and media when the main system is in a standby mode. Data can be displayed on cell phones and other network-connected devices via Bluetooth and other connectivity options; the display can be updated with a number of different kinds of information, such as contacts, maps and email. This can be consulted while the mobile PC is otherwise powered down. Since the underlying platform is so power-efficient, it can run for hundreds of hours without draining a notebook battery, while still providing always-on access to data and multimedia content. SideShow is coupled to the Windows Vista Sidebar capability – that is, Sidebar Gadgets are ported to be compatible with SideShow secondary display applications.
However and silicon providers can provide native capabilities to allow for richer multimedia applications such as text, image and video decode / playback. For example, a notebook with an in-lid display could be used as an MP3 player while powered down, with the notebook battery providing hundreds of hours of playback time because of the low power footprint that the Sideshow platform maintains. According to Microsoft, Gadgets were discontinued because they have "serious vulnerabilities", "could be exploited to harm your computer, access your computer's files, show you objectionable content, or change their behavior at any time". Gadgets were removed in Windows 8. However, with the launch of Windows 10, widespread support for Gadgets led to their revival as third-party enhancements to the new operating system, which adjusted to take account of them, including a link to the Gadgets Sidebar in the Windows Control Panel. Many hundreds are now more are in active development. Dashboard Widget engine Live.com Windows Sidebar Windows SideShow Windows Desktop Gadgets Scott Isaacs Lal, Rajesh.
DBase was one of the first database management systems for microcomputers, the most successful in its day. The dBase system includes the core database engine, a query system, a forms engine, a programming language that ties all of these components together. DBase's underlying file format, the.dbf file, is used in applications needing a simple format to store structured data. DBase was published by Ashton-Tate for microcomputer operating system CP/M in 1980, ported to Apple II and IBM PC computers running DOS. On the PC platform, in particular, dBase became one of the best-selling software titles for a number of years. A major upgrade was released as dBase III, ported to a wider variety of platforms, adding UNIX, VMS. By the mid-1980s, Ashton-Tate was one of the "big three" software publishers in the early business software market, the others being Lotus Development and WordPerfect. Starting in the mid-1980s, several companies produced their own variations on the dBase product and the dBase programming language.
These included FoxBASE+, other so-called xBase products. Many of these could not push it aside in the market; this changed with the disastrous introduction of dBase IV, whose design and stability were so poor that many users switched to other products. At the same time, there was growing use of IBM-invented SQL in database products. Another factor was user adoption of Microsoft Windows on desktop computers; the shift toward SQL and Windows put pressure on the makers of xBase products to invest in major redesign to provide new capabilities. In the early 1990s xBase products constituted the leading database platform for implementing business applications; the size and impact of the xBase market did not go unnoticed, within one year, the three top xBase firms were acquired by larger software companies: Borland purchased Ashton-Tate Microsoft bought Fox Software, Computer Associates acquired Nantucket. By the following decade most of the original xBase products had faded from prominence and several disappeared.
Products known as dBase still exist, owned by dBase LLC. In the late 1960s, Fred Thompson at the Jet Propulsion Laboratory was using a Tymshare product named RETRIEVE to manage a database of electronic calculators, which were at that time expensive products. In 1971 Thompson collaborated with Jack Hatfield, a programmer at JPL, to write an enhanced version of RETRIEVE which became the JPLDIS project. JPLDIS was written in FORTRAN on the UNIVAC 1108 mainframe, was presented publicly in 1973; when Hatfield left JPL in 1974, Jeb Long took over his role. While working at JPL as a contractor, C. Wayne Ratliff entered the office football pool, he had no interest in the game, but felt he could win the pool by processing the post-game statistics found in newspapers. In order to do this, he turned his attention to a database system and, by chance, came across the documentation for JPLDIS, he used this as the basis for a port to PTDOS on his kit-built IMSAI 8080 microcomputer, called the resulting system Vulcan.
George Tate and Hal Lashlee had built two successful start-up companies: Discount Software, one of the first to sell PC software programs through the mail to consumers, Software Distributors, one of the first wholesale distributors of PC software in the world. They entered into an agreement with Ratliff to market Vulcan, formed Ashton-Tate to do so. Ratliff ported Vulcan from PTDOS to CP/M. Hal Pawluk, who handled marketing for the nascent company, decided to change the name to the more business-like "dBase". Pawluk all-caps "BASE" to create a distinctive name. Pawluk suggested calling the new product version two to suggest it was less buggy than an initial release. DBASE II became a standard CP/M application along with WordStar and SuperCalc. In 1981, IBM commissioned a port of dBase for the then-in-development PC; the resultant program was one of the initial pieces of software available when the IBM PC went on sale the fall of 1981. DBase was one of a few "professional" programs on the platform at that time, became a huge success.
The customer base included not only end-users, but an increasing number of "value added resellers", or VARs, who purchased dBase, wrote applications with it, sold the completed systems to their customers. The May 1983 release of dBase II RunTime further entrenched dBase in the VAR market by allowing the VARs to deploy their products using the lower-cost RunTime system. Although some critics stated that dBase was difficult to learn, its success created many opportunities for third parties. By 1984 more than 1,000 companies offered dBase-related application development, libraries of code to add functionality, applications using dBase II Runtime, consulting and how-to books. A company in San Diego premiered a magazine devoted to professional use of dBase, Data Based Advisor. All of these activities fueled the rapid rise of dBase as the leading product of its type. Adam B. Green helped popularize dBase II via his "dBase II User's Guide" - which he authored and self-published courses he taught on the subject his Boston-based SoftwareBanc - one of the first software-only mail-order housesThere were some legal "difficulties" with Ashton-Tate, publisher of the dBase II software.
As platforms and operating systems proliferated in the early 1980s, the company found it difficult to port the assembly language-based dBase to target systems. This led to a re-writ
Microsoft Corporation is an American multinational technology company with headquarters in Redmond, Washington. It develops, licenses and sells computer software, consumer electronics, personal computers, related services, its best known software products are the Microsoft Windows line of operating systems, the Microsoft Office suite, the Internet Explorer and Edge web browsers. Its flagship hardware products are the Xbox video game consoles and the Microsoft Surface lineup of touchscreen personal computers; as of 2016, it is the world's largest software maker by revenue, one of the world's most valuable companies. The word "Microsoft" is a portmanteau of "microcomputer" and "software". Microsoft is ranked No. 30 in the 2018 Fortune 500 rankings of the largest United States corporations by total revenue. Microsoft was founded by Bill Gates and Paul Allen on April 4, 1975, to develop and sell BASIC interpreters for the Altair 8800, it rose to dominate the personal computer operating system market with MS-DOS in the mid-1980s, followed by Microsoft Windows.
The company's 1986 initial public offering, subsequent rise in its share price, created three billionaires and an estimated 12,000 millionaires among Microsoft employees. Since the 1990s, it has diversified from the operating system market and has made a number of corporate acquisitions, their largest being the acquisition of LinkedIn for $26.2 billion in December 2016, followed by their acquisition of Skype Technologies for $8.5 billion in May 2011. As of 2015, Microsoft is market-dominant in the IBM PC-compatible operating system market and the office software suite market, although it has lost the majority of the overall operating system market to Android; the company produces a wide range of other consumer and enterprise software for desktops and servers, including Internet search, the digital services market, mixed reality, cloud computing and software development. Steve Ballmer replaced Gates as CEO in 2000, envisioned a "devices and services" strategy; this began with the acquisition of Danger Inc. in 2008, entering the personal computer production market for the first time in June 2012 with the launch of the Microsoft Surface line of tablet computers.
Since Satya Nadella took over as CEO in 2014, the company has scaled back on hardware and has instead focused on cloud computing, a move that helped the company's shares reach its highest value since December 1999. In 2018, Microsoft surpassed Apple as the most valuable publicly traded company in the world after being dethroned by the tech giant in 2010. Childhood friends Bill Gates and Paul Allen sought to make a business utilizing their shared skills in computer programming. In 1972 they founded their first company, named Traf-O-Data, which sold a rudimentary computer to track and analyze automobile traffic data. While Gates enrolled at Harvard, Allen pursued a degree in computer science at Washington State University, though he dropped out of school to work at Honeywell; the January 1975 issue of Popular Electronics featured Micro Instrumentation and Telemetry Systems's Altair 8800 microcomputer, which inspired Allen to suggest that they could program a BASIC interpreter for the device. After a call from Gates claiming to have a working interpreter, MITS requested a demonstration.
Since they didn't yet have one, Allen worked on a simulator for the Altair while Gates developed the interpreter. Although they developed the interpreter on a simulator and not the actual device, it worked flawlessly when they demonstrated the interpreter to MITS in Albuquerque, New Mexico. MITS agreed to distribute it, marketing it as Altair BASIC. Gates and Allen established Microsoft on April 4, 1975, with Gates as the CEO; the original name of "Micro-Soft" was suggested by Allen. In August 1977 the company formed an agreement with ASCII Magazine in Japan, resulting in its first international office, "ASCII Microsoft". Microsoft moved to a new home in Bellevue, Washington in January 1979. Microsoft entered the operating system business in 1980 with its own version of Unix, called Xenix. However, it was MS-DOS. After negotiations with Digital Research failed, IBM awarded a contract to Microsoft in November 1980 to provide a version of the CP/M OS, set to be used in the upcoming IBM Personal Computer.
For this deal, Microsoft purchased a CP/M clone called 86-DOS from Seattle Computer Products, which it branded as MS-DOS, though IBM rebranded it to PC DOS. Following the release of the IBM PC in August 1981, Microsoft retained ownership of MS-DOS. Since IBM had copyrighted the IBM PC BIOS, other companies had to reverse engineer it in order for non-IBM hardware to run as IBM PC compatibles, but no such restriction applied to the operating systems. Due to various factors, such as MS-DOS's available software selection, Microsoft became the leading PC operating systems vendor; the company expanded into new markets with the release of the Microsoft Mouse in 1983, as well as with a publishing division named Microsoft Press. Paul Allen resigned from Microsoft in 1983 after developing Hodgkin's disease. Allen claimed that Gates wanted to dilute his share in the company when he was diagnosed with Hodgkin's disease because he didn't think he was working hard enough. After leaving Microsoft, Allen lost billions of dollars on ill-conceived or mistimed technology investments.
He invested in low-tech sectors, sports teams, commercial real estate. Despite having begun jointly developing a new operating system, OS/2, with IBM in
Delphi is an integrated development environment for rapid application development of desktop, mobile and console software, developed by Embarcadero Technologies. It is an event-driven language. Delphi's compilers use their own Object Pascal dialect of Pascal and generate native code for Microsoft Windows, macOS, iOS, Android and Linux. Since 2016, there have been new releases of Delphi every six months, with new platforms being added every second release. Delphi includes a code editor, a visual designer, an integrated debugger, a source code control component, support for third-party plugins; the code editor features Code Insight, Error Insight, refactoring. The visual forms designer has traditionally used Visual Component Library for native Windows development, but the FireMonkey platform was added for cross-platform development. Database support in Delphi is strong. A Delphi project of a million lines to compile in a few seconds – one benchmark gave 170,000 lines per second. Delphi was developed by Borland as a rapid application development tool for Windows as the successor of Turbo Pascal.
Delphi added full object-oriented programming to the existing language, since the language has grown to support generics and anonymous methods, native Component Object Model support. In 2006, Borland’s developer tools section was transferred from Borland to a wholly owned subsidiary known as CodeGear, sold to Embarcadero Technologies in 2008. In 2015, Embarcadero was purchased by Idera Software, but the Embarcadero mark was retained for the developer tools division. Delphi and its C++ counterpart, C++Builder, are interoperable, they share many core components, notably the IDE, VCL, much of the runtime library. In addition, they can be used jointly in a project. For example, C++Builder 6 and can consume Delphi source code and C++ in one project, while packages compiled with C++Builder can be used from within Delphi. In 2007, the products were released jointly as RAD Studio, a shared host for Delphi and C++Builder, which can be purchased with either or both. Delphi supports rapid application development.
Among the features supporting RAD are the visual designer. Delphi uses, it supports native cross-compilation. Its visual designer has traditionally used Visual Component Library for RAD. To better support development for Microsoft Windows and interoperate with code developed with other software development tools, Delphi supports independent interfaces of Component Object Model with reference counted class implementations, support for many third-party components. Interface implementations can be delegated to properties of classes. Message handlers are implemented by tagging a method of a class with the integer constant of the message to handle. Database connectivity is extensively supported through the many VCL database-aware and database access components. Versions have included upgraded and enhanced runtime library routines provided by the community group FastCode, established in 2003. Delphi is a typed high-level programming language, intended to be easy to use and based on the earlier Object Pascal language.
Pascal was developed as a general-purpose language "suitable for expressing the fundamental constructs known at the time in a concise and logical way", "its implementation was to be efficient and competitive with existing FORTRAN compilers" but without low-level programming facilities or access to hardware. Turbo Pascal and its descendants, including Delphi, support access to hardware and low-level programming, with the facility to incorporate code written in assembly language and other languages. Delphi's object orientation features only class- and interface-based polymorphism. Metaclasses are first class objects. Objects are references to the objects, which Delphi implicitly de-references, so there is no need to manually allocate memory for pointers to objects or use similar techniques that some other languages need. There are dedicated reference-counted string types, null-terminated strings. Strings can be concatenated by using the'+' operator, rather than using functions. For dedicated string types Delphi handles memory management without programmer intervention.
Since Borland Developer Studio 2006 there are functions to locate memory leaks. Delphi includes an integrated IDE; the Delphi products all ship including most of its source code. Third-party components and tools to enhance the IDE or for other Delphi related development tasks are available, some free of charge; the IDE includes a GUI for localization and translation of created programs that may be deployed to a translator. The VCL framework maintains a high level of source compatibility between versions, which simplifies updating existing source code to a newer Delphi version. Third-party libraries may need updates from the vendor but, if source code is supplied, recompilation with the newer version may be sufficient; the VCL was an early adopter of dependency inversion of control. With class helpers new functionality can be introduced to core RTL and VCL classes without changing the original source code of the RTL or VCL; the compiler is single pass. It can optionally compile to a single executable.
Delphi can generate standard DLLs, ActiveX DLLs, COM automation serv
A database is an organized collection of data stored and accessed electronically from a computer system. Where databases are more complex they are developed using formal design and modeling techniques; the database management system is the software that interacts with end users and the database itself to capture and analyze the data. The DBMS software additionally encompasses; the sum total of the database, the DBMS and the associated applications can be referred to as a "database system". The term "database" is used to loosely refer to any of the DBMS, the database system or an application associated with the database. Computer scientists may classify database-management systems according to the database models that they support. Relational databases became dominant in the 1980s; these model data as rows and columns in a series of tables, the vast majority use SQL for writing and querying data. In the 2000s, non-relational databases became popular, referred to as NoSQL because they use different query languages.
Formally, a "database" refers to the way it is organized. Access to this data is provided by a "database management system" consisting of an integrated set of computer software that allows users to interact with one or more databases and provides access to all of the data contained in the database; the DBMS provides various functions that allow entry and retrieval of large quantities of information and provides ways to manage how that information is organized. Because of the close relationship between them, the term "database" is used casually to refer to both a database and the DBMS used to manipulate it. Outside the world of professional information technology, the term database is used to refer to any collection of related data as size and usage requirements necessitate use of a database management system. Existing DBMSs provide various functions that allow management of a database and its data which can be classified into four main functional groups: Data definition – Creation and removal of definitions that define the organization of the data.
Update – Insertion 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 made available in a form the same as it is stored in the database or in a new form obtained by altering or combining existing data from the database. Administration – Registering and monitoring users, enforcing data security, monitoring performance, maintaining data integrity, dealing with concurrency control, recovering information, corrupted by some event such as an unexpected system failure. Both a database and its DBMS conform to the principles of a particular database model. "Database system" refers collectively to the database model, database management system, database. Physically, database servers are dedicated computers that hold the actual databases and run only the DBMS and related software. Database servers are multiprocessor computers, with generous memory and RAID disk arrays used for stable storage.
RAID is used for recovery of data. Hardware database accelerators, connected to one or more servers via a high-speed channel, are 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 rely on a standard operating system to provide these functions. Since DBMSs comprise a significant market and storage vendors take into account DBMS requirements in their own development plans. Databases and DBMSs can be categorized according to the database model that they support, the type of computer they run on, the query language used to access the database, their internal engineering, which affects performance, scalability and security; the sizes and performance of databases and their respective DBMSs have grown in orders of magnitude. These performance increases were enabled by the technology progress in the areas of processors, computer memory, computer storage, computer networks.
The development of database technology can be divided into three eras based on data model or structure: navigational, SQL/relational, post-relational. The two main early navigational data models were the hierarchical model and the CODASYL model The relational model, first proposed in 1970 by Edgar F. Codd, departed from this tradition by insisting that applications should search for data by content, rather than by following links; the relational model employs sets of ledger-style tables, each used for a different type of entity. Only in the mid-1980s did computing hardware become powerful enough to allow the wide deployment of relational systems. By the early 1990s, relational systems dominated in all large-scale data processing applications, as of 2018 they remain dominant: IBM DB2, Oracle, MySQL, Microsoft SQL Server are the most searched DBMS; the dominant database language, standardised SQL for the relational model, has influenced database languages for other data models. Object databases were developed in the 1980s to overcome the inconvenience of object-relational impedance mismatch, which led to the coining of the term "post-relational" and the development of hybrid object-relational databas