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Software
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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
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Computer hardware
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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
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Operating system
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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
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Web browser
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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
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Abstraction (software engineering)
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In software engineering and computer science, abstraction is a technique for arranging complexity of computer systems. It works by establishing a level of complexity on which a person interacts with the system, the programmer works with an idealized interface and can add additional levels of functionality that would otherwise be too complex to handle. In addition, a task of sending a message across continents would be extremely complex if the programmer had to start with a piece of fiber optic cable. By using layers of complexity that have created to abstract away the physical cables and network layout, and presenting the programmer with a virtual data channel. Abstraction can apply to control or to data, Control abstraction is the abstraction of actions while data abstraction is that of data structures, Control abstraction involves the use of subroutines and control flow abstractions Data abstraction allows handling pieces of data in meaningful ways. For example, it is the motivation behind the datatype. The notion of an object in object-oriented programming can be viewed as a way to combine abstractions of data, the same abstract definition can be used as a common interface for a family of objects with different implementations and behaviors but which share the same meaning. The inheritance mechanism in object-oriented programming can be used to define a class as the common interface. The recommendation that programmers use abstractions whenever suitable in order to avoid duplication is known as the abstraction principle, the requirement that a programming language provide suitable abstractions is also called the abstraction principle. Computing mostly operates independently of the world, The hardware implements a model of computation that is interchangeable with others. The software is structured in architectures to enable humans to create the enormous systems by concentrating on a few issues at a time and these architectures are made of specific choices of abstractions. Greenspuns Tenth Rule is an aphorism on how such an architecture is both inevitable and complex, a central form of abstraction in computing is language abstraction, new artificial languages are developed to express specific aspects of a system. Computer languages can be processed with a computer, an example of this abstraction process is the generational development of programming languages from the machine language to the assembly language and the high-level language. Each stage can be used as a stone for the next stage. The language abstraction continues for example in scripting languages and domain-specific programming languages, within a programming language, some features let the programmer create new abstractions. These include subroutines, modules, polymorphism, and software components, some other abstractions such as software design patterns and architectural styles remain invisible to a translator and operate only in the design of a system. Some abstractions try to limit the range of concepts a programmer needs to be aware of, some abstractions are designed to interoperate with other abstractions - for example, a programming language may contain a foreign function interface for making calls to the lower-level language. Different programming languages provide different types of abstraction, depending on the applications for the language
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Computer architecture
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In computer engineering, computer architecture is a set of rules and methods that describe the functionality, organization, and implementation of computer systems. Some definitions of architecture define it as describing the capabilities and programming model of a computer, in other definitions computer architecture involves instruction set architecture design, microarchitecture design, logic design, and implementation. The first documented computer architecture was in the correspondence between Charles Babbage and Ada Lovelace, describing the analytical engine, johnson had the opportunity to write a proprietary research communication about the Stretch, an IBM-developed supercomputer for Los Alamos National Laboratory. Brooks went on to develop the IBM System/360 line of computers. Later, computer users came to use the term in many less-explicit ways, the earliest computer architectures were designed on paper and then directly built into the final hardware form. The discipline of architecture has three main subcategories, Instruction Set Architecture, or ISA. The ISA defines the code that a processor reads and acts upon as well as the word size, memory address modes, processor registers. Microarchitecture, or computer organization describes how a processor will implement the ISA. The size of a computers CPU cache for instance, is an issue that generally has nothing to do with the ISA, system Design includes all of the other hardware components within a computing system. These include, Data processing other than the CPU, such as memory access Other issues such as virtualization, multiprocessing. There are other types of computer architecture, E. g. the C, C++, or Java standards define different Programmer Visible Macroarchitecture. UISA —a group of machines with different hardware level microarchitectures may share a common microcode architecture, pin Architecture, The hardware functions that a microprocessor should provide to a hardware platform, e. g. the x86 pins A20M, FERR/IGNNE or FLUSH. Also, messages that the processor should emit so that external caches can be invalidated, pin architecture functions are more flexible than ISA functions because external hardware can adapt to new encodings, or change from a pin to a message. The term architecture fits, because the functions must be provided for compatible systems, the purpose is to design a computer that maximizes performance while keeping power consumption in check, costs low relative to the amount of expected performance, and is also very reliable. For this, many aspects are to be considered which includes Instruction Set Design, Functional Organization, Logic Design, the implementation involves Integrated Circuit Design, Packaging, Power, and Cooling. Optimization of the design requires familiarity with Compilers, Operating Systems to Logic Design, an instruction set architecture is the interface between the computers software and hardware and also can be viewed as the programmers view of the machine. Computers do not understand high level languages such as Java, C++, a processor only understands instructions encoded in some numerical fashion, usually as binary numbers. Software tools, such as compilers, translate those high level languages into instructions that the processor can understand, besides instructions, the ISA defines items in the computer that are available to a program—e. g
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Software development process
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In software engineering, a software development methodology is splitting of software development work into distinct phases containing activities with the intent of better planning and management. It is often considered a subset of the development life cycle. The methodology may include the pre-definition of specific deliverables and artifacts that are created and completed by a team to develop or maintain an application. For example, there are many software development processes that fit the spiral life-cycle model. A variety of such frameworks have evolved over the years, each with its own recognized strengths, one software development methodology framework is not necessarily suitable for use by all projects. Each of the available methodology frameworks are best suited to specific kinds of projects, based on technical, organizational, project. Software development organizations implement process methodologies to ease the process of development, sometimes, contractors may require methodologies employed, an example is the U. S. defense industry, which requires a rating based on process models to obtain contracts. The international standard for describing the method of selecting, implementing and monitoring the life cycle for software is ISO/IEC12207, a decades-long goal has been to find repeatable, predictable processes that improve productivity and quality. Some try to systematize or formalize the seemingly unruly task of designing software, others apply project management techniques to designing software. Organizations may create a Software Engineering Process Group, which is the point for process improvement. These details are not dictated by the choice of model or general methodology. The software development methodology framework didnt emerge until the 1960s, according to Elliott the systems development life cycle can be considered to be the oldest formalized methodology framework for building information systems. The main target of this framework in the 1960s was to develop large scale functional business systems in an age of large scale business conglomerates. Information systems activities revolved around heavy data processing and number crunching routines, in some cases a sponsor or maintenance organization distributes an official set of documents that describe the process. Specific examples include, 1970s Structured programming since 1969 Cap Gemini SDM, originally from PANDATA, several software development approaches have been used since the origin of information technology, in two main categories. Typically an approach or a combination of approaches is chosen by management or a development team, Royce in 1970 although Royce did not use the term waterfall in this article. The basic principles are, Project is divided into phases, with some overlap. Emphasis is on planning, time schedules, target dates, budgets, written documentation is an explicit deliverable of each phase
