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    Computer Types

    Wikipedia. (2013, September 15). Classes of computers. Retrieved from http://en.wikipedia.org/wiki/Classes_of_computers


    Microcomputers (personal computers)

    Microcomputers are the most common kind of computers used by people today, whether in a workplace, at school or on the desk at home. The term “microcomputer” was introduced with the advent of single chip microprocessors. The term "microcomputer" itself is now practically an anachronism.

    These computers include:


    • Desktop computers
    • In-car computers
    • Game consoles


    A separate class is that of mobile devices:



    Mainframe computers

    The term mainframe computer was created to distinguish the traditional, large, institutional computer intended to service multiple users from the smaller, single user machines. These computers are capable of handling and processing very large amounts of data quickly. Mainframe computers are used in large institutions such as government, banks and large corporations. They are measured in MIPS (million instructions per second) and respond to up to 100s of millions of users at a time.


    Supercomputers

    A supercomputer is focused on performing tasks involving intense numerical calculations such as weather forecasting, fluid dynamics, nuclear simulations, theoretical astrophysics, and complex scientific computations. A supercomputer is a computer that is at the frontline of current processing capacity, particularly speed of calculation. The term supercomputer itself is rather fluid, and the speed of today's supercomputers tends to become typical of tomorrow's ordinary computer. Supercomputer processing speeds are measured in floating point operations per second, or FLOPS. An example of a floating point operation is the calculation of mathematical equations in real numbers. In terms of computational capability, memory size and speed, I/O technology, and topological issues such as bandwidth and latency, supercomputers are the most powerful, are very expensive, and not cost-effective just to perform batch or transaction processing. Transaction processing is handled by less powerful computers such as server computers or mainframes.

    Servers

    Server usually refers to a computer that is dedicated to provide a service. For example, a computer dedicated to a databasemay be called a "database server". "File servers" manage a large collection of computer files. "Web servers" process web pagesand web applications. Many smaller servers are actually personal computers that have been dedicated to provide services for other computers.


    Workstations

    Workstations are computers that are intended to serve one user and may contain special hardware enhancements not found on a personal computer.


    Information appliances

    Information appliances are computers specially designed to perform a specific user-friendly function—such as playing music,photography, or editing text. The term is most commonly applied to mobile devices, though there are also portable and desktop devices of this class.


    Embedded computers

    Embedded computers are computers that are a part of a machine or device. Embedded computers generally execute a program that is stored in non-volatile memory and is only intended to operate a specific machine or device. Embedded computers are very common. Embedded computers are typically required to operate continuously without being reset or rebooted, and once employed in their task the software usually cannot be modified. An automobile may contain a number of embedded computers; however, a washing machine and a DVD player would contain only one. The central processing units(CPUs) used in embedded computers are often sufficient only for the computational requirements of the specific application and may be slower and cheaper than CPUs found in a personal computer.



    Supercomputer

    From Wikipedia, the free encyclopedia


    Wikipedia. (2013, September 15). Supercomputer. Retrieved from http://en.wikipedia.org/wiki/Supercomputer


    A supercomputer is a computer at the frontline of contemporary processing capacity--particularly speed of calculation.


    Supercomputers were introduced in the 1960s, designed initially and, for decades, primarily by Seymour Cray at Control Data Corporation(CDC), Cray Research and subsequent companies bearing his name or monogram. While the supercomputers of the 1970s used only a few processors, in the 1990s machines with thousands of processors began to appear and, by the end of the 20th century, massively parallel supercomputers with tens of thousands of "off-the-shelf" processors were the norm.[2][3] As of June 2013, China's Tianhe-2 supercomputer is the fastest in the world at 33.86 petaFLOPS.


    Systems with massive numbers of processors generally take one of two paths: In one approach (e.g., in distributed computing), a large number of discrete computers (e.g., laptops) distributed across a network (e.g., the internet) devote some or all of their time to solving a common problem; each individual computer (client) receives and completes many small tasks, reporting the results to a central server which integrates the task results from all the clients into the overall solution.[4][5] In another approach, a large number of dedicated processors are placed in close proximity to each other (e.g. in a computer cluster); this saves considerable time moving data around and makes it possible for the processors to work together (rather than on separate tasks), for example in mesh and hypercube architectures.


    The use of multi-core processors combined with centralization is an emerging trend; one can think of this as a small cluster (the multicore processor in a smartphone, tablet, laptop, etc.) that both depends upon and contributes to the cloud.[6][7]


    Supercomputers play an important role in the field of computational science, and are used for a wide range of computationally intensive tasks in various fields, including quantum mechanics, weather forecasting, climate research, oil and gas exploration,molecular modeling (computing the structures and properties of chemical compounds, biological macromolecules, polymers, and crystals), and physical simulations (such as simulations of the early moments of the universe, airplane and spacecraft aerodynamics, the detonation of nuclear weapons, and nuclear fusion). Throughout their history, they have been essential in the field of counter-cryptography.[8]


    Hardware and architecture

    Approaches to supercomputer architecture have taken dramatic turns since the earliest systems were introduced in the 1960s. Early supercomputer architectures pioneered bySeymour Cray relied on compact innovative designs and local parallelism to achieve superior computational peak performance.[9] However, in time the demand for increased computational power ushered in the age of massively parallel systems.


    While the supercomputers of the 1970s used only a few processors, in the 1990s, machines with thousands of processors began to appear and by the end of the 20th century, massively parallel supercomputers with tens of thousands of "off-the-shelf" processors were the norm. Supercomputers of the 21st century can use over 100,000 processors (some being graphic units) connected by fast connections.[2][3]


    Throughout the decades, the management of heat density has remained a key issue for most centralized supercomputers.[22][23][24] The large amount of heat generated by a system may also have other effects, e.g. reducing the lifetime of other system components.[25] There have been diverse approaches to heat management, from pumping Fluorinert through the system, to a hybrid liquid-air cooling system or air cooling with normal air conditioning temperatures.[15][26]



    The CPU share of TOP500

    Systems with a massive number of processors generally take one of two paths: in one approach, known as grid computing, the processing power of a large number of computers in distributed, diverse administrative domains, is opportunistically used whenever a computer is available. In another approach, a large number of processors are used in close proximity to each other, e.g. in a computer cluster. In such a centralized massively parallel system the speed and flexibility of the interconnect becomes very important and modern supercomputers have used various approaches ranging from enhanced Infiniband systems to three-dimensional torus interconnects. 


    A number of "special-purpose" systems have been designed, dedicated to a single problem. This allows the use of specially programmed FPGA chips or even custom VLSI chips, allowing better price/performance ratios by sacrificing generality. Examples of special-purpose supercomputers include Belle, Deep Blue, and Hydra, for playing chess, Gravity Pipe for astrophysics,[37] MDGRAPE-3 for protein structure computation molecular dynamics and Deep Crack, for breaking theDES cipher.


    Operating systems

    Since the end of the 20th century, supercomputer operating systems have undergone major transformations, as sea changes have taken place in supercomputer architecture. While early operating systems were custom tailored to each supercomputer to gain speed, the trend has been to move away from in-house operating systems to the adaptation of generic software such asLinux.


    Given that modern massively parallel supercomputers typically separate computations from other services by using multiple types of nodes, they usually run different operating systems on different nodes, e.g. using a small and efficient lightweight kernel such as CNK or CNL on compute nodes, but a larger system such as a Linux-derivative on server and I/O nodes.


    Opportunistic approaches

    Opportunistic Supercomputing is a form of networked grid computing whereby a “super virtual computer” of many loosely coupled volunteer computing machines performs very large computing tasks. Grid computing has been applied to a number of large-scale embarrassingly parallel problems that require supercomputing performance scales. However, basic grid and cloud computing approaches that rely on volunteer computing can not handle traditional supercomputing tasks such as fluid dynamic simulations.


    Performance metrics

    Top supercomputer speeds: logscale speed over 60 years

    In general, the speed of supercomputers is measured and benchmarked in "FLOPS" (FLoating Point Operations Per Second), and not in terms of MIPS, i.e. as "instructions per second", as is the case with general purpose computers.[69] These measurements are commonly used with an SI prefix such as tera-, combined into the shorthand "TFLOPS" (1012 FLOPS, pronounced teraflops), or peta-, combined into the shorthand "PFLOPS" (1015 FLOPS, pronouncedpetaflops.) "Petascale" supercomputers can process one quadrillion (1015) (1000 trillion) FLOPS. Exascale is computing performance in the exaflops range. An exaflop is one quintillion (1018) FLOPS (one million teraflops).


    No single number can reflect the overall performance of a computer system.


    The TOP500 list

    Pie Chart of Supercomputer Countries Share as of Nov 2012

    Since 1993, the fastest supercomputers have been ranked on the TOP500 list according to their LINPACK benchmark results. The list does not claim to be unbiased or definitive, but it is a widely cited current definition of the "fastest" supercomputer available at any given time.


    Year

    Supercomputer

    Peak speed

    (Rmax)

    Location

    2011

    Fujitsu K computer

    10.51 PFLOPS

    Kobe, Japan

    2012

    Cray Titan

    17.59 PFLOPS

    Oak Ridge, USA

    2013

    NUDT Tianhe-2

    33.86 PFLOPS

    Guangzhou, China


    Applications of supercomputers

    The stages of supercomputer application may be summarized in the following table:

    Decade

    Uses and computer involved

    1970s

    Weather forecasting, aerodynamic research (Cray-1).[72]

    1980s

    Probabilistic analysis,[73] radiation shielding modeling[74] (CDC Cyber).

    1990s

    Brute force code breaking (EFF DES cracker),[75]

    2000s

    3D nuclear test simulations as a substitute for legal conduct Nuclear Proliferation Treaty (ASCI Q).[76]

    2010s

    Molecular Dynamics Simulation (Tianhe-1A)[77]


    The IBM Blue Gene/P computer has been used to simulate a number of artificial neurons equivalent to approximately one percent of a human cerebral cortex, containing 1.6 billion neurons with approximately 9 trillion connections. The same research group also succeeded in using a supercomputer to simulate a number of artificial neurons equivalent to the entirety of a rat's brain.


    Modern-day weather forecasting also relies on supercomputers. The National Oceanic and Atmospheric Administration uses supercomputers to crunch hundreds of millions of observations to help make weather forecasts more accurate.


    In 2011, the challenges and difficulties in pushing the envelope in supercomputing were underscored by IBM's abandonment of the Blue Waters petascale project.



    Mainframe computer

    From Wikipedia, the free encyclopedia


    Wikipedia. (2013, September 18). Mainframe computer. Retrieved from https://en.wikipedia.org/wiki/Mainframe_computer


    Mainframe computers (colloquially referred to as "big iron"[1]) are computers used primarily by corporate and governmental organizations for critical applications, bulk data processing such as census, industry and consumer statistics, enterprise resource planning and transaction processing. The term originally referred to the large cabinets that housed the central processing unit and main memory of early computers.[2][3] Later, the term was used to distinguish high-end commercial machines from less powerful units.[4] Most large-scale computer system architectures were established in the 1960s, but continue to evolve.


    Description

    Modern mainframe design is generally less defined by single-task computational speed (typically defined as MIPS rate or FLOPS in the case of floating point calculations), and more by:


    • Redundant internal engineering resulting in high reliability and security
    • Extensive input-output facilities with the ability to offload to separate engines
    • Strict backward compatibility with older software
    • High hardware and computational utilization rates through virtualization to support massive throughput


    In the late 1950s, most mainframes had no explicitly interactive interface. They accepted sets of punched cards, paper tape, or magnetic tape to transfer data and programs. They operated in batch mode to support back office functions, such as customer billing, and supported interactive terminals almost exclusively for applications rather than program development. 


    Historically, mainframes acquired their name in part because of their substantial size, and because of requirements for specialized heating, ventilation, and air conditioning (HVAC), and electrical power, essentially posing a "main framework.”


    Characteristics

    Mainframes can add or hot swap system capacity without disrupting system function, with specificity and granularity to a level of sophistication not usually available with most server solutions Modern mainframes, notably the IBM zSeries, System z9 and System z10 servers, offer two levels of virtualization: logical partitions (LPARs, via the PR/SM facility) and virtual machines (via the z/VM operating system). Many mainframe customers run two machines: one in their primary data center, and one in their backup data center—fully active, partially active, or on standby—in case there is a catastrophe affecting the first building. 


    Market

    IBM mainframes dominate the mainframe market at well over 90% market share.[8] Unisys manufactures ClearPath mainframes, based on earlier Burroughs products and ClearPath mainframes based on Sperry Univac OS 1100 product lines. In 2002, Hitachi co-developed the zSeries z800 with IBM to share expenses, but subsequently the two companies have not collaborated on new Hitachi models. Hewlett-Packard sells its unique NonStop systems, which it acquired with Tandem Computers and which some analysts classify as mainframes. Groupe Bull's DPS, Fujitsu (formerly Siemens) BS2000, and Fujitsu-ICL VME mainframes are still available in Europe. Fujitsu, Hitachi, and NEC (the "JCMs") still maintain mainframe hardware businesses in the Japanese market.


    Differences from supercomputers

    A supercomputer is a computer that is at the frontline of current processing capacity, particularly speed of calculation. Supercomputers are used for scientific and engineering problems (high-performance computing) which are data crunching and number crunching, while mainframes are used for transaction processing. The differences are as follows:


    • Mainframes are often approximately measured in millions of instructions per second (MIPS), but supercomputers are measured in floating point operations per second (FLOPS) and more recently by traversed edges per second or TEPS.
    • Mainframes are built to be reliable for transaction processing as it is commonly understood in the business world: a commercial exchange of goods, services, or money. A typical transaction, as defined by the Transaction Processing Performance Council,[24] would include the updating to a database system for such things as inventory control (goods), airline reservations (services), or banking (money). 




    Personal computer

    From Wikipedia, the free encyclopedia


    Wikipedia. (2013, September 19). Personal computer. Retrieved from http://en.wikipedia.org/wiki/Personal_computer


    A personal computer (PC) is a general-purpose computer, whose size, capabilities, and original sale price makes it useful for individuals, and which is intended to be operated directly by an end-user with no intervening computer operator. This contrasted with the batch processing or time-sharing models which allowed larger, more expensive minicomputer and mainframe systems to be used by many people, usually at the same time. Large data processing systems require a full-time staff to operate efficiently.

    Software applications for most personal computers include, but are not limited to, word processing, spreadsheets, databases, Web browsers and e-mail clients, digital media playback, games, and myriad personal productivity and special-purpose software applications. Modern personal computers often have connections to the Internet, allowing access to the World Wide Web and a wide range of other resources. 


    Today's users have access to a wide range of commercial software, freeware and free and open-source software, which is provided in ready-to-run or ready-to-compile form. Since the early 1990s, Microsoft operating systems and Intel hardware have dominated much of the personal computer market, first with MS-DOS and then with the "Wintel" (Windows + Intel) combination. Popular alternatives to Microsoft's Windows operating systems include Apple's OS X and the free open-source Linux and BSD operating systems. 


    Workstation

    A workstation is a high-end personal computer designed for technical, mathematical, or scientific applications. Intended primarily to be used by one person at a time, they are commonly connected to a local area network and run multi-user operating systems. Workstations are used for tasks such as computer-aided design, drafting and modeling, computation-intensive scientific and engineering calculations, image processing,architectural modeling, and computer graphics for animation and motion picture visual effects.[38]


    Desktop computer

    Prior to the wide spread usage of PCs, a computer that could fit on a desk was remarkably small. Today the phrase usually indicates a particular style of computer case. Desktop computers come in a variety of styles ranging from large vertical tower cases to small form factor models that can be tucked behind an LCD monitor. In this sense, the term 'desktop' refers specifically to a horizontally oriented case, usually intended to have the display screen placed on top to save space on the desk top. Most modern desktop computers have separate screens and keyboards.


    Gaming computer

    A gaming computer is a standard desktop computer that typically has high-performance hardware, such as a more powerful video card, processor, and memory, in order to handle the requirements of demanding video games. A number of companies, such as Alienware, manufacture prebuilt gaming computers, and companies such as Razer and Logitechmarket mice, keyboards, and headsets geared towards gamers.


    Single unit

    Single unit PCs (also known as all-in-one PCs) are a subtype of desktop computers, which combine the monitor and case of the computer within a single unit. The monitor often utilizes a touchscreen as an optional method of user input, however detached keyboards and mice are normally still included. The inner components of the PC are often located directly behind the monitor, and many are built similarly to laptops.


    Laptop

    A laptop computer or simply laptop, also called a notebook computer, is a small personal computer designed for portability. Usually all of the interface hardware needed to operate the laptop, such as USB ports (previously parallel and serial ports), graphics card, sound channel, etc., are built in to a single unit. Laptops contain high capacity batteries that can power the device for extensive periods of time, enhancing portability. Once the battery charge is depleted, it will have to be recharged through a power outlet. In the interest of saving power, weight and space, they usually share RAM with the video channel, slowing their performance compared to an equivalent desktop machine. For this reason, Desktop or Gaming computers are generally preferred to laptop PCs for gaming purposes.


    One main drawback of the laptop is sometimes, due to the size and configuration of components, relatively little can be done to upgrade the overall computer from its original design. Internal upgrades are either not manufacturer recommended, can damage the laptop if done with poor care or knowledge, or in some cases impossible, making the desktop PC more modular. Some internal upgrades, such as memory and hard disks upgrades are often easy, a display or keyboard upgrade is usually impossible. The laptop has the same access as the desktop to the wide variety of devices, such as external displays, mice, cameras, storage devices and keyboards, which may be attached externally through USB ports and other less common ports such as external video.


    A subtype of notebooks, called subnotebooks, are computers with most of the features of a standard laptop computer but smaller. They are larger than hand-held computers, and usually run full versions of desktop/laptop operating systems. Ultra-Mobile PCs(UMPC) are usually considered subnotebooks, or more specifically, subnotebook Tablet PCs (see below). 


    Netbook

    Netbooks (also called mini notebooks or subnotebooks) are a rapidly evolving category of small, light and inexpensive laptop computers suited for general computing and accessing web-based applications; they are often marketed as "companion devices," that is, to augment a user's other computer access.  Walt Mossberg called them a "relatively new category of small, light, minimalist and cheap laptops." By August 2009, CNET called netbooks "nothing more than smaller, cheaper notebooks.".


    Initially, their primary defining characteristic was the lack of an optical disc drive, requiring it to be a separate and external device. This has become less important as flash memory devices have gradually increased in capacity, replacing the writable optical disc (e.g. CD-RW, DVD-RW) as a transportable storage medium.


    At their inception in late 2007 — as smaller notebooks optimized for low weight and low cost[42] — netbooks omitted key features (e.g., the optical drive), featured smaller screens and keyboards, and offered reduced specification and computing power. Over the course of their evolution, netbooks have ranged in size from below 5 in[43] to over 13 in,[44] and from ~1 kg (2-3 pounds). Often significantly less expensive than other laptops,[45] by mid-2009, netbooks had been offered to users "free of charge", with an extended service contract purchase of a cellular data plan.[46]


    Tablet PC

    A tablet PC is a notebook or slate-shaped mobile computer. Its touchscreen or graphics tablet/screen hybrid technology allows the user to operate the computer with a stylus or digital pen, or a fingertip, instead of a keyboard or mouse. The form factor offers a more mobile way to interact with a computer. Tablet PCs are often used where normal notebooks are impractical or unwieldy, or do not provide the needed functionality. Recently, tablet PCs have been given operating systems normally used on phones, like Android or iOS. This gives them many of the same uses as a phone, but with more power and functionality.


    Ultra-mobile PC

    The ultra-mobile PC (UMPC) is a specification for a small form factor of tablet PCs. It was developed as a joint development exercise by Microsoft, Intel, and Samsung, among others. Current UMPCs typically feature the Windows XP, Windows Vista, Windows 7, or Linux operating system and low-voltage Intel Atom or VIA C7-M processors.


    Hardware

    Hardware is a comprehensive term for all of the physical parts of a computer, as distinguished from the data it contains or operates on, and the software that provides instructions for the hardware to accomplish tasks. The boundary between hardware and software is slightly blurry - firmware is software that is "built-in" to the hardware.

    Mass-market consumer computers use highly standardized components and so are simple for an end user to assemble into a working system. A typical desktop computer consists of a computer case which holds the power supply,motherboard, hard disk and often an optical disc drive. External devices such as a computer monitor or visual display unit, keyboard, and a pointing device are usually found in a personal computer.


    The motherboard connects all processor, memory and peripheral devices together. The RAM, graphics card and processor are mounted directly onto the motherboard. The central processing unit microprocessor chip plugs into a socket. Expansion memory plugs into memory sockets. Some motherboards have the video display adapter, sound and other peripherals integrated onto the motherboard, while others use expansion slots for graphics cards, network cards, or other I/O devices. 


    The hardware capabilities of personal computers can sometimes be extended by the addition of expansion cards connected via an expansion bus. Some standard peripheral buses often used for adding expansion cards in personal computers as of 2005 are PCI,AGP (a high-speed PCI bus dedicated to graphics adapters), and PCI Express. Most personal computers as of 2005 have multiple physical PCI expansion slots. Many also include an AGP bus and expansion slot or a PCI Express bus and one or more expansion slots, but few PCs contain both buses.


    Processor

    The central processing unit, or CPU, is that part of a computer which executes software program instructions. In newer PCs the CPU is about a million transistors in one integrated circuit chip called the microprocessor. The microprocessor plugs into the motherboard. The chip generates so much heat that the PC builder is required to attach a special cooling device to its surface. Modern CPUs are equipped with a fan attached via heat sink.


    IBM PC compatible computers use an x86-compatible microprocessor. Intel, AMD, VIA Technologies or Transmeta manufacture them. Apple Macintosh computers were initially built with the Motorola 680x0 family of processors, then switched to the PowerPC series. In 2006 they switched to x86-compatible processors by Intel.


    Motherboard

    A motherboard without processor, memory and extension cards, cables

    The motherboard, also referred to as system board or main board, is the primary circuit board within a personal computer. Other major system components plug directly onto or cable into the motherboard. A motherboard will contain a microprocessor, the CPU supporting circuitry (mostly integrated circuits) that provide the interface between memory and input/output peripheral circuits, main memory, and facilities for initial setup of the computer immediately after power-on (often called boot firmware or, in IBM PC compatible computers, a BIOS). In many portable and embedded personal computers, the motherboard houses nearly all of the PC's core components. Often a motherboard will also contain one or more peripheral buses and physical connectors for expansion purposes. Sometimes a secondary daughter board is connected to the motherboard to provide further expandability or to satisfy space constraints.


    Main memory

    A PC's main memory is fast storage that is directly accessible by the CPU, and is used to store the currently executing program and immediately needed data. PCs use semiconductor random access memory (RAM) of various kinds such as DRAM, SDRAM orSRAM as their primary storage. Which exact kind depends on cost/performance issues at any particular time. Main memory is much faster than mass storage devices like hard disksor optical discs, but is usually volatile, meaning it does not retain its contents (instructions or data) in the absence of power, and is much more expensive for a given capacity than is most mass storage. Main memory is generally not suitable for long-term or archival data storage.


    Hard disk

    Mass storage devices store programs and data even when the power is off; they do require power to perform read and write functions during usage. Although flash memory has dropped in cost, the prevailing form of mass storage in personal computers is still the hard disk. The disk drives use a sealed head/disk assembly (HDA) which was first introduced by IBM's "Winchester" disk system. The use of a sealed assembly allowed the use of positive air pressure to drive out particles from the surface of the disk, which improves reliability.


    If the mass storage controller provides for expandability, a PC may also be upgraded by the addition of extra hard disk or optical disc drives. For example, BD-ROMs, DVD-RWs, and various optical disc recorders may all be added by the user to certain PCs. Standard internal storage device connection interfaces are PATA, Serial ATA, and SCSI.

    Solid state drives or SSD has begun replacing traditional mechanical hard drives.


    Visual display unit

    A visual display unit, or "computer monitor", or just display, is a piece of electrical equipment, usually separate from the computer case, which displays visual images without producing a permanent computer record. A display device is usually either a CRT or some form of flat panel such as a TFT LCD.


    The display unit houses the circuitry that generates its picture from signals sent from the computer. Within the computer, either integral to the motherboard, or plugged into it as an Expansion card, there is pre-processing circuitry to convert the microprocessor's output data to a format compatible with the display unit's circuitry.

    The images from computer monitors originally contained only text, but as graphical user interfaces emerged and became common, they began to display more images and multimedia content.


    Video card

    The video card—otherwise called a graphics card, graphics adapter or video adapter—processes the graphics output from the motherboard and transmits it to the display. It is an essential part of modern multimedia computing.

    On older models, and today on budget models, graphics circuitry may be integrated with the motherboard, but for modern and flexible machines, they are connected by the PCI,AGP, or PCI Express interface.


    Keyboard

    A "Model M" IBM computer keyboard from the early 1980s. Commonly called the "Clicky Keyboard" due to its buckling spring key spring design, which gives the keyboard its iconic 'Click' sound with each keystroke.

    In computing, a keyboard is an arrangement of buttons that each correspond to a function, letter, or number. They are the primary devices of inputting text. In most cases, they contain an array of keys specifically organized with the corresponding letters, numbers, and functions printed or engraved on the button. They are generally designed around an operators language, and many different versions for different languages exist. In English, the most common layout is the QWERTY layout, which was originally used in typewriters


    Mouse

    A Mouse on a computer is a small, slideable device that users hold and slide around to point at, click on, and sometimes drag objects on screen in a graphical user interface using a pointer on screen. Almost all Personal Computers have mice. It may be plugged into a computer's rear mouse socket, or as a USB device, or, more recently, may be connected wirelessly via a USB antenna or Bluetooth antenna. In the past, they had a single button that users could press down on the device to "click" on whatever the pointer on the screen was hovering over. Now, however, many Mice have two or three buttons(possibly more); a "right click" function button on the mouse, which performs a secondary action on a selected object, and a scroll wheel, which users can rotate using their fingers to "scroll" up or down. 


    Mice traditionally detected movement and communicated with the computer with an internal "mouse ball"; and used optical encoders to detect rotation of the ball and tell the computer where the mouse has moved. However, these systems were subject to low durability, accuracy and required internal cleaning. Modern mice use optical technology to directly trace movement of the surface under the mouse and are much more accurate, durable and almost maintenance free. They work on a wider variety of surfaces and can even operate on walls, ceilings or other non-horizontal surfaces.


    Mass storage

    All computers require either fixed or removable storage for their operating system, programs and user generated material.


    Formerly the 5¼ inch and 3½ inch floppy drive were the principal forms of removable storage for backup of user files and distribution of software.


    As memory sizes increased, the capacity of the floppy did not keep pace; the Zip drive and other higher-capacity removable media were introduced but never became as prevalent as the floppy drive.


    By the late 1990s the optical drive, in CD and later DVD and Blu-ray Disc, became the main method for software distribution, and writeable media provided backup and file interchange. Floppy drives have become uncommon in desktop personal computers since about 2000, and were dropped from many laptop systems even earlier.[note 1]

    Early home computers used compact audio cassettes for file storage; these were at the time a very low cost storage solution, but were displaced by floppy disk drives when manufacturing costs dropped, by the mid-1980s.

    Interchange of data such as photographs from digital cameras is greatly expedited by installation of a card reader, which often is compatible with several forms of flash memory. It is usually faster and more convenient to move large amounts of data by removing the card from the mobile device, instead of communicating with the mobile device through aUSB interface.


    A USB flash drive today performs much of the data transfer and backup functions formerly done with floppy drives, Zip disks and other devices. Main-stream current operating systems for personal computers provide standard support for flash drives, allowing interchange even between computers using different processors and operating systems. The compact size and lack of moving parts or dirt-sensitive media, combined with low cost for high capacity, have made flash drives a popular and useful accessory for any personal computer user.


    Computer communications


    Common peripherals and adapter cards


    Toxicity

    Toxic chemicals found in computer hardware include lead, mercury, cadmium, chromium, plastic (PVC), and barium. A computer is about 17% lead, copper, zinc, mercury, and cadmium; 23% is plastic, 14% is aluminum, and 20% is iron.


    Lead is found in a cathode ray tube (CRT) display, and on all of the printed circuit boards and most expansion cards. Mercury is located in the screen's fluorescent lamp, in the laser light generators in the optical disk drive, and in the round, silver batteries on the motherboard. Plastic found mostly in the housing of the computation and display circuitry.


    Software

    Computer software is any kind of computer program, procedure, or documentation that performs some task on a computer system.[49] The term includes application software such as word processors which perform productive tasks for users, system software such as operating systems, which interface with computer hardware to provide the necessary services for application software, and middleware which controls and co-ordinates distributed systems.


    Software applications for word processing, Internet browsing, Internet faxing, e-mail and other digital messaging, multimedia playback, computer game play and computer programming are common. The user of a modern personal computer may have significant knowledge of the operating environment and application programs, but is not necessarily interested in programming nor even able to write programs for the computer. Therefore, most software written primarily for personal computers tends to be designed with simplicity of use, or "user-friendliness" in mind. However, the software industry continuously provide a wide range of new products for use in personal computers, targeted at both the expert and the non-expert user.


    Operating system

    An operating system (OS) manages computer resources and provides programmers with an interface used to access those resources. An operating system processes system data and user input, and responds by allocating and managing tasks and internal system resources as a service to users and programs of the system. An operating system performs basic tasks such as controlling and allocating memory, prioritizing system requests, controlling input and output devices, facilitating computer networking and managing files.


    Common contemporary desktop OSs are Microsoft Windows, OS X, Linux, Solaris and FreeBSD. Windows, Mac, and Linux all have server and personal variants. With the exception of Microsoft Windows, the designs of each of the aforementioned OSs were inspired by, or directly inherited from, the Unix operating system. Unix was developed at Bell Labs beginning in the late 1960s and spawned the development of numerous free and proprietary operating systems.


    Microsoft Windows

    Main article: Microsoft Windows

    Microsoft Windows is the collective brand name of several software operating systems by Microsoft. Microsoft first introduced an operating environment named Windows in November 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces (GUIs)[50][51] generated by Apple's 1984 introduction of the Macintosh. The most recent client and server version of Windows are Windows 8 and Windows Server 2012, respectively, which have been available at retail since 26 October '12. This includes Windows XP, Vista. 7 and 8. Also all the severs.


    OS X

    OS X (formerly Mac OS X) is a line of operating systems developed, marketed, and sold by Apple Inc.. OS X is the successor to the original Mac OS, which had been Apple's primary operating system since 1984. OS X is a Unix-based graphical operating system. The most recent version of OS X is OS X Mountain Lion. This includes Snow Leopard, Leopard, Lion, Mountain Lion and the new Mavericks.


    Linux

    Linux is a family of Unix-like computer operating systems. Linux is one of the most prominent examples of free software and open source development: typically all underlying source code can be freely modified, used, and redistributed by anyone.[52] The name "Linux" comes from the Linux kernel, started in 1991 by Linus Torvalds. The system'sutilities and libraries usually come from the GNU operating system, announced in 1983 byRichard Stallman. The GNU contribution is the basis for the alternative nameGNU+Linux.[53]


    Known for its use in servers as part of the LAMP application stack, Linux is supported by corporations such as Dell, Hewlett-Packard, IBM, Novell, Oracle Corporation, Red Hat,Canonical Ltd. and Sun Microsystems. It is used as an operating system for a wide variety of computer hardware, including desktop computers, netbooks, supercomputers,[54] video game systems, such as the PlayStation 3 (until this option was removed remotely by Sony in 2010[55]), several arcade games, and embedded devices such as mobile phones, portable media players, routers, and stage lighting systems.


    Applications

    A computer user will apply application software to carry out a specific task. System software supports applications and provides common services such as memory management, network connectivity, or device drivers; all of which may be used by applications but which are not directly of interest to the end user. A simple, if imperfect analogy in the world of hardware would be the relationship of an electric light bulb (an application) to an electric power generation plant (a system). The power plant merely generates electricity, not itself of any real use until harnessed to an application like the electric light that performs a service that benefits the user.


    Typical examples of software applications are word processors, spreadsheets, and media players. Multiple applications bundled together as a package are sometimes referred to as an application suite. Microsoft Office and OpenOffice.org, which bundle together a word processor, a spreadsheet, and several other discrete applications, are typical examples. The separate applications in a suite usually have a user interface that has some commonality making it easier for the user to learn and use each application. And often they may have some capability to interact with each other in ways beneficial to the user. For example, a spreadsheet might be able to be embedded in a word processor document even though it had been created in the separate spreadsheet application.




    Smartphone

    From Wikipedia, the free encyclopedia


    Wikipedia. (2013, September 19). Smartphone. Retrieved from https://en.wikipedia.org/wiki/Smartphone


    A smartphone, or smart phone, is a mobile phone built on a mobile operating system, with more advanced computing capability and connectivity than a feature phone.[1][2][3] The first smartphones combined the functions of a personal digital assistant (PDA) with a mobile phone. Later models added the functionality of portable media players, low-end compact digital cameras, pocket video cameras, and GPS navigation units to form one multi-use device. Many modern smartphones also include high-resolution touchscreens and web browsers that display standard web pages as well as mobile-optimized sites. High-speed data access is provided by Wi-Fi and mobile broadband. In recent years, the rapid development of mobile app markets and of mobile commerce have been drivers of smartphone adoption.


    The mobile operating systems (OS) used by modern smartphones include Google's Android, Apple's iOS, Nokia's Symbian, Blackberry Ltd's BlackBerry OS, Samsung's Bada, Microsoft's Windows Phone, Hewlett-Packard's webOS, and embedded Linux distributions such as Maemo and MeeGo. Such operating systems can be installed on many different phone models, and typically each device can receive multiple OS software updates over its lifetime. A few other upcoming operating systems are Mozilla's Firefox OS, Canonical Ltd.'s Ubuntu Phone, and Tizen.


    Worldwide sales of smartphones exceeded those of feature phones in early 2013.[4] As of July 18, 2013, 90 percent of global handset sales are attributed to the purchase of Android and iPhone smartphones.[5]


    Display

    Screens on smartphones vary largely in both display size and display resolution. The most common screen sizes range from 3 inches to over 5 inches (measured diagonally). Some 6- to 8-inch screen devices exist that run on mobile OSes and have the ability to make phone calls, such as Huawei Ascend Mate (6.1 in), Sony Xperia Z Ultra (6.4 in), Huawei MediaPad 7 Vogue (7 in), Asus Fonepad (7 in) and Samsung Galaxy Note 8.0 (8 in).


    Common resolutions for smartphone screens vary from 240×320 (QVGA) pixels to 1080×1920 (Full HD), with flagship Android phones commonly sporting full HD, 1080p displays and the iPhone 5 at 640×1136. By late-2012 and early 2013, the trend was for full HD 1080p smartphone screens for the highest-end handsets.


    With the passing of the years, Pixel density of smartphone screen is getting higher. Apple branded high-density display as Retina. High-density display is worthwhile for small complex characters (especially East Asian text) and sharp edges (especially Line arts and Aliased fonts).

    Android[68]

    iPhone

    Windows Phone[69]

    note

    ldpi (120dpi, Android 1.6 or later)


    Windows Phone 7 96dpi



    Windows Phone 7 131dpi


    mdpi (160dpi)

    iPhone 1/3/3GS (163dpi)



    tvdpi (213dpi, Android 3.2 or later)


    Windows Phone 7 192dpi

    Lumia 820/900 (217dpi)


    hdpi (240dpi, Android 1.6 or later)

    Nexus One (254dpi)/Nexus S (235dpi)


    Windows Phone 7 262dpi

    Lumia 710/Lumia 800 (252dpi)


    xhdpi (320dpi, Android 2.2 or later)

    Galaxy Nexus (316dpi)/Nexus 4 (320dpi)

    iPhone 4/4S/5 (326dpi)

    Lumia 920 (332dpi)


    xxhdpi (480dpi, Android 4.1 or later)



    5-inch Full-HD (440ppi)

    4.7-inch Full-HD (468ppi)


    Camera

    Smartphone cameras are progressively improving: Higher pixel resolution and ISO speed sensor, lower F-number (bright and fast) lens, and better digital image processing for noise reduction.

    pixel resolution

    device (pixel resolution, sensor size, 35 mm equiv. focal length, F-number)

    40MP

    Nokia Lumia 1020 (41MP, 1/1.5”, 25mm, f/2.2), Nokia 808 Pureview (41MP, 1/1.2”, 26mm, f/2.4)

    20MP

    Sony Xperia Z1 (20.7MP, 1/2.3”, 27mm, f/2.0)

    10MP

    Lenovo K900 (13MP, ?”, ?mm, f/1.8), Samsung Galaxy S4 (13MP, 1/3.06”, 31mm, f/2.2), Motorola Moto X (10MP, 1/2.6”, 30mm, f/2.4)

    8MP

    iPhone 5S (8MP, 1/3”, 29.7mm, f/2.2)[74]

    4MP

    HTC One (4MP, 1/3”, 28mm, f/2.0)


    Radio and television

    Some smartphones support FM radio, but noise-sensitive AM radio is usually not supported. In some regions, such as Japan and Korea, most smartphones support mobile digital broadcasts (1seg or T-DMB), while some smartphones support regular digital broadcasts.


    Smartphone usage

    For several years, the demand for smartphones has outpaced other products on the mobile phone market.[83] According to a 2012 survey, around half of U.S. mobile consumers own smartphones. They could account for around 70% of all U.S. mobile devices by 2013;[84] in the 25 to 34 age group, smartphone ownership is so far reported at 62%.[85] For the third quarter of 2011, the NPD Group reported that in the U.S., the proportion of handset sales that were made up of smartphones reached 59% for consumers aged 18 and over.[86]


    Until the end of November 2011, 27% of all photographs were taken with camera-equipped smartphones, a significant increase from 17% in 2010. For many people, smartphones have replaced Point-and-shoot cameras.[91] A study conducted in September 2012 concluded that 4 out of 5 smartphone owners (85.9 million U.S. users) use the device to shop.[92]



    By manufacturer

    Smartphone Customer Satisfaction

    by J.D. Power and Associates

    Apple 2010

      

    810

    Apple 2011

      

    838

    HTC 2010

      

    727

    HTC 2011

      

    801

    Industry Average 2010

      

    753

    Industry Average 2011

      

    788

    Samsung 2010

      

    724

    Samsung 2011

      

    777

    Motorola 2010


    N/A

    Motorola 2011

      

    775

    RIM 2010

      

    741

    RIM 2011

      

    762

    LG 2010


    N/A

    LG 2011

      

    760

    HP/Palm 2010

      

    712

    HP/Palm 2011

      

    733

    Nokia 2010

      

    720

    Nokia 2011

      

    721

    Rankings are based on a possible top score of 1000


    Starting with the launch of their Communicator model in 1996, until 2011 Nokia was dominant in the smartphone market, though the company has more recently been joined by other competitors in the market. Based on a report by Strategy Analytics, Samsung overtook Nokia in smartphone shipments with an estimated 27.8 million units shipped in Q3 2011[96] (Samsung does not publicly disclose the numbers of their smartphone shipments and sales).

    For the first time in Q2 2011, Apple surpassed Nokia worldwide by revenue and profit, with Apple's profit share of the total worldwide smartphone market increasing to 66.3% while Nokia reported a loss.[97]


    Data released by StatCounter, a research group that tracks Internet usage by browser, platform and device, on September 9, 2013 showed that Samsung is more widely used than Apple's handsets for mobile web browsing. For the month of August, Samsung worldwide accounted for 26.59% of mobile Internet use, compared to 23.39% for Apple.[102]


    By operating system

    2010 saw the rapid rise of the Google Android operating system from 4% of new deployments in 2009 to 33% at the beginning of 2011 making it share the top position with the since long dominating Symbian OS. The smaller rivals include Blackberry OS, iOS, Samsung's recently introduced Bada, HP's heir of Palm webOS and the Microsoft Windows Phone OS, which is now supported by Nokia. In the UK, which currently has one of the highest penetrations of smartphones in the World, Android achieved 50% market share in October 2011.[103] As of the end of Q1 2013, Android was the top operating system worldwide smartphone market, with a 75% market share, followed by iOS with 17.3%, and Windows Phone with 3.2%.[104][105] Forecasts show that by 2017 Windows Phone will be approaching second place, with 12.7% market share, while Android and iOS will remain in their previous positions, with 67.1% and 14.1% respectively.[106]


    Historical sales figures (in millions of units)


    Year

    Android (Google)

    Blackberry (RIM)

    iOS (Apple)

    Linux (other than Android)

    Palm/WebOS (Palm/HP)

    Symbian (Nokia)

    Asha Full Touch (Nokia)

    Windows Mobile/Phone (Microsoft)

    Bada (Samsung)

    Other

    2007[107]


    11.77

    3.3

    11.76

    1.76

    77.68


    14.7



    2008[107]


    23.15

    11.42

    11.26

    2.51

    72.93


    16.5



    2009[108]

    6.8

    34.35

    24.89

    8.13

    1.19

    80.88


    15.03



    2010[109]

    67.22

    47.45

    46.6



    111.58


    12.38




    2011[110]

    219.52

    51.54

    89.26



    93.41


    8.77


    14.24


    2012-Q1[111]

    81.07

    9.94

    33.12



    12.47


    2.71

    3.84

    1.24

    2012-Q2[112]

    104.8

    7.4

    26.0

    3.5


    6.8


    5.4


    0.1

    2012-Q3[113]

    122.5

    9.0

    23.6



    4.4

    6.5[114]

    4.1

    5.1

    0.7

    2012-Q4[115]

    144.7

    7.3

    43.5



    2.6

    9.3[116]

    6.2

    2.7

    0.7

    2013-Q1[117]

    162.1

    6.3

    37.4



    __

    --

    7.0

    --

    --

    2013-Q2[118]

    177.9

    6.2

    31.9



    .631

    --

    7.4

    .838

    .471


    Malicious software attacks

    As smartphone adoption increases, these devices become more appealing to attackers who try to infect them with malicious software(malware).[123][124] Smartphone security literature suggests that smartphone malware can be written even by average developers.[125]


    Smartphone malware is more easily distributed through application stores that have minimal or no security mechanisms, such as app kill switch (aka remote app removal), review process for their content, etc.[126][127] Often malware is hidden in pirated versions of legitimate apps, which are then distributed through 3rd party app stores.[128][129] Malware risk also comes from what's known as an "update attack," where a legitimate application is later changed to include a malware component, which users then install when they are notified that the app has been updated. Additionally, the ability to acquire software directly from links on the web results in a distribution vector called "malvertizing," where users are directed to click on links, such as on ads that look legitimate, which then open in the device's web browser and download and install malware automatically.[130]


    Typical smartphone malware leverages platform vulnerabilities that allow it to gain root access on the device in the background. Using this access the malware installs additional software to target communications, location, or other personal identifying information. A common form of malware on mobile phones is the SMS trojan, which sends premium SMS messages, possibly while unknowingly running in the background of a legitimate application. These premium SMS messages run up charges on the owner's phone bill that cannot be recovered.


    In August 2010, Kaspersky Lab reported detection of the first malicious program for smartphones running on Google's Android operating system, named Trojan-SMS.AndroidOS.FakePlayer.a, an SMS trojan that had already infected a number of devices using that OS.[131] Over the spring of 2011 Android malware increased 76%, according to McAfee.[123][132] A report from Juniper Global Threat Center notes that malware on the Android platform increased 400% from 2009 to the summer of 2010, and then saw a 472% increase between July and November 2011.[126] The Juniper report indicates that 55% of Android malware acts as spyware, and 44% are SMS trojans.

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