computer computer system redirects here for other uses see computer disambiguation and computer system disambiguation computer computers and computing devices from different eras a computer is a device that can be instructed to carry out sequences of arithmetic or logical operations automatically via computer programming modern computers have the ability to follow generalized sets of operations called programs these programs enable computers to perform an extremely wide range of tasks computers are used as control systems for a wide variety of industrial and consumer devices this includes simple special purpose devices like microwave ovens and remote controls factory devices such as industrial robots and computeraided design and also general purpose devices like personal computers and mobile devices such as smartphones early computers were only conceived as calculating devices since ancient times simple manual devices like the abacus aided people in doing calculations early in the industrial revolution some mechanical devices were built to automate long tedious tasks such as guiding patterns for looms more sophisticated electrical machines did specialized analog calculations in the early 20th century the first digital electronic calculating machines were developed during world war ii the speed power and versatility of computers have been increasing dramatically ever since then conventionally a modern computer consists of at least one processing element typically a central processing unit cpu and some form of memory the processing element carries out arithmetic and logical operations and a sequencing and control unit can change the order of operations in response to stored information peripheral devices include input devices keyboards mice joystick etc output devices monitor screens printers etc and inputoutput devices that perform both functions eg the 2000sera touchscreen peripheral devices allow information to be retrieved from an external source and they enable the result of operations to be saved and retrieved etymology a female computer with microscope and calculator 1952 according to the oxford english dictionary the first known use of the word computer was in 1613 in a book called the yong mans gleanings by english writer richard braithwait i haue the online etymology dictionary gives the first attested use of computer in the 1640s history history of computing hardware pre20th century the ishango bone devices have been used to aid computation for thousands of years mostly using onetoone correspondence with fingers the earliest counting device was probably a form of tally stick later record keeping aids throughout the fertile crescent included calculi clay spheres cones etc which represented counts of items probably livestock or grains sealed in hollow unbaked clay containers the use of counting rods is one example the chinese suanpan the number represented on this abacus is 6302715408 the abacus was initially used for arithmetic tasks the roman abacus was developed from devices used in babylonia as early as 2400 bc since then many other forms of reckoning boards or tables have been invented in a medieval european counting house a checkered cloth would be placed on a table and markers moved around on it according to certain rules as an aid to calculating sums of money the ancient greekdesigned antikythera mechanism dating between 150 and 100 bc is the worlds oldest analog computer the antikythera mechanism is believed to be the earliest mechanical analog computer according to derek j de solla price it was designed to calculate astronomical positions it was discovered in 1901 in the antikythera wreck off the greek island of antikythera between kythera and crete and has been dated to c100 bc devices of a level of complexity comparable to that of the antikythera mechanism would not reappear until a thousand years later many mechanical aids to calculation and measurement were constructed for astronomical and navigation use the planisphere was a star chart invented by ab rayhn albrn in the early 11th century c1000 ad the sector a calculating instrument used for solving problems in proportion trigonometry multiplication and division and for various functions such as squares and cube roots was developed in the late 16th century and found application in gunnery surveying and navigation the planimeter was a manual instrument to calculate the area of a closed figure by tracing over it with a mechanical linkage a slide rule the slide rule was invented around 16201630 shortly after the publication of the concept of the logarithm it is a handoperated analog computer for doing multiplication and division as slide rule development progressed added scales provided reciprocals squares and square roots cubes and cube roots as well as transcendental functions such as logarithms and exponentials circular and hyperbolic trigonometry and other functions slide rules with special scales are still used for quick performance of routine calculations such as the e6b circular slide rule used for time and distance calculations on light aircraft in the 1770s pierre jaquetdroz a swiss watchmaker built a mechanical doll automaton that could write holding a quill pen by switching the number and order of its internal wheels different letters and hence different messages could be produced in effect it could be mechanically programmed to read instructions along with two other complex machines the doll is at the muse dart et dhistoire of neuchtel switzerland and still operates the tidepredicting machine invented by sir william thomson in 1872 was of great utility to navigation in shallow waters it used a system of pulleys and wires to automatically calculate predicted tide levels for a set period at a particular location the differential analyser a mechanical analog computer designed to solve differential equations by integration used wheelanddisc mechanisms to perform the integration in 1876 lord kelvin had already discussed the possible construction of such calculators but he had been stymied by the limited output torque of the ballanddisk integrators in a differential analyzer the output of one integrator drove the input of the next integrator or a graphing output the torque amplifier was the advance that allowed these machines to work starting in the 1920s vannevar bush and others developed mechanical differential analyzers first computing device a portion of babbages difference engine charles babbage an english mechanical engineer and polymath originated the concept of a programmable computer considered the father of the computer the machine was about a century ahead of its time all the parts for his machine had to be made by hand this was a major problem for a device with thousands of parts eventually the project was dissolved with the decision of the british government to cease funding babbages failure to complete the analytical engine can be chiefly attributed to difficulties not only of politics and financing but also to his desire to develop an increasingly sophisticated computer and to move ahead faster than anyone else could follow nevertheless his son henry babbage completed a simplified version of the analytical engines computing unit the mill in 1888 he gave a successful demonstration of its use in computing tables in 1906 analog computers sir william thomsons third tidepredicting machine design 187981 during the first half of the 20th century many scientific computing needs were met by increasingly sophisticated analog computers which used a direct mechanical or electrical model of the problem as a basis for computation however these were not programmable and generally lacked the versatility and accuracy of modern digital computers the art of mechanical analog computing reached its zenith with the differential analyzer built by h l hazen and vannevar bush at mit starting in 1927 this built on the mechanical integrators of james thomson and the torque amplifiers invented by h w nieman a dozen of these devices were built before their obsolescence became obvious by the 1950s the success of digital electronic computers had spelled the end for most analog computing machines but analog computers remained in use during the 1950s in some specialized applications such as education control systems and aircraft slide rule digital computers electromechanical by 1938 the united states navy had developed an electromechanical analog computer small enough to use aboard a submarine this was the torpedo data computer which used trigonometry to solve the problem of firing a torpedo at a moving target during world war ii similar devices were developed in other countries as well replica of zuses z3 the first fully automatic digital electromechanical computer early digital computers were electromechanical electric switches drove mechanical relays to perform the calculation these devices had a low operating speed and were eventually superseded by much faster allelectric computers originally using vacuum tubes the z2 created by german engineer konrad zuse in 1939 was one of the earliest examples of an electromechanical relay computer in 1941 zuse followed his earlier machine up with the z3 the worlds first working electromechanical programmable fully automatic digital computer vacuum tubes and digital electronic circuits purely electronic circuit elements soon replaced their mechanical and electromechanical equivalents at the same time that digital calculation replaced analog the engineer tommy flowers working at the post office research station in london in the 1930s began to explore the possible use of electronics for the telephone exchange experimental equipment that he built in 1934 went into operation five years later converting a portion of the telephone exchange network into an electronic data processing system using thousands of vacuum tubes colossus the first electronic digital programmable computing device was used to break german ciphers during world war ii during world war ii the british at bletchley park achieved a number of successes at breaking encrypted german military communications the german encryption machine enigma was first attacked with the help of the electromechanical bombes which were often run by women colossus was the worlds first electronic digital programmable computer eniac was the first electronic turingcomplete device and performed ballistics trajectory calculations for the united states army the usbuilt eniac it combined the high speed of electronics with the ability to be programmed for many complex problems it could add or subtract 5000 times a second a thousand times faster than any other machine it also had modules to multiply divide and square root high speed memory was limited to 20 words about 80 bytes built under the direction of john mauchly and j presper eckert at the university of pennsylvania eniacs development and construction lasted from 1943 to full operation at the end of 1945 the machine was huge weighing 30 tons using 200 kilowatts of electric power and contained over 18000 vacuum tubes 1500 relays and hundreds of thousands of resistors capacitors and inductors modern computers concept of modern computer the principle of the modern computer was proposed by alan turing in his seminal 1936 paper turing machines are to this day a central object of study in theory of computation except for the limitations imposed by their finite memory stores modern computers are said to be turingcomplete which is to say they have algorithm execution capability equivalent to a universal turing machine stored programs a section of the manchester baby the first electronic storedprogram computer early computing machines had fixed programs changing its function required the rewiring and restructuring of the machine the manchester baby was the worlds first storedprogram computer it was built at the victoria university of manchester by frederic c williams tom kilburn and geoff tootill and ran its first program on 21 june 1948 the mark 1 in turn quickly became the prototype for the ferranti mark 1 the worlds first commercially available generalpurpose computer and ran the worlds first regular routine office computer job transistors a bipolar junction transistor the bipolar transistor was invented in 1947 from 1955 onwards transistors replaced vacuum tubes in computer designs giving rise to the second generation of computers compared to vacuum tubes transistors have many advantages they are smaller and require less power than vacuum tubes so give off less heat silicon junction transistors were much more reliable than vacuum tubes and had longer indefinite service life transistorized computers could contain tens of thousands of binary logic circuits in a relatively compact space at the university of manchester a team under the leadership of tom kilburn designed and built a machine using the newly developed transistors instead of valves integrated circuits the next great advance in computing power came with the advent of the integrated circuit the idea of the integrated circuit was first conceived by a radar scientist working for the royal radar establishment of the ministry of defence geoffrey wa dummer dummer presented the first public description of an integrated circuit at the symposium on progress in quality electronic components in washingtondc on 7 may 1952 the first practical ics were invented by jack kilby at texas instruments and robert noyce at fairchild semiconductor his chip solved many practical problems that kilbys had not produced at fairchild semiconductor it was made of silicon whereas kilbys chip was made of germanium this new development heralded an explosion in the commercial and personal use of computers and led to the invention of the microprocessor while the subject of exactly which device was the first microprocessor is contentious partly due to lack of agreement on the exact definition of the term microprocessor it is largely undisputed that the first singlechip microprocessor was the intel 4004 mobile computers the first mobile computers were heavy and ran from mains power the 50lb ibm 5100 was an early example later portables such as the osborne 1 and compaq portable were considerably lighter but still needed to be plugged in the first laptops such as the grid compass removed this requirement by incorporating batteries and with the continued miniaturization of computing resources and advancements in portable battery life portable computers grew in popularity in the 2000s the same developments allowed manufacturers to integrate computing resources into cellular phones these smartphones and tablets run on a variety of operating systems and soon became the dominant computing device on the market with manufacturers reporting having shipped an estimated 237 million devices in 2q 2013 types computers are typically classified based on their uses based on uses analog computer digital computer hybrid computer based on sizes smartphone microcomputer workstation personal computer laptop minicomputer mainframe computer supercomputer hardware computer hardware personal computer hardware central processing unit and microprocessorplay media video demonstrating the standard components of a slimline computer the term hardware covers all of those parts of a computer that are tangible physical objects circuits computer chips graphic cards sound cards memory ram motherboard displays power supplies cables keyboards printers and mice input devices are all hardware history of computing hardware history of computing hardware first generation mechanicalelectromechanical calculators pascals calculator arithmometer difference engine quevedos analytical machines programmable devices jacquard loom analytical engine ibm asccharvard mark i harvard mark ii ibm ssec z1 z2 z3 second generation vacuum tubes calculators atanasoffberry computer ibm 604 univac 60 univac 120 programmable devices colossus eniac manchester baby edsac manchester mark 1 ferranti pegasus ferranti mercury csirac edvac univac i ibm 701 ibm 702 ibm 650 z22 third generation discrete transistors and ssi msi lsi integrated circuits mainframes ibm 7090 ibm 7080 ibm system360 bunch minicomputer hp 2116a ibm system32 ibm system36 linc pdp8 pdp11 desktop computer programma 101 hp 9100 fourth generation vlsi integrated circuits minicomputer vax ibm system i 4bit microcomputer intel 4004 intel 4040 8bit microcomputer intel 8008 intel 8080 motorola 6800 motorola 6809 mos technology 6502 zilog z80 16bit microcomputer intel 8088 zilog z8000 wdc 6581665802 32bit microcomputer intel 80386 pentium motorola 68000 arm 64bit microcomputer alpha mips parisc powerpc sparc x8664 armv8a embedded computer intel 8048 intel 8051 personal computer desktop computer home computer laptop computer personal digital assistant pda portable computer tablet pc wearable computer theoreticalexperimental quantum computer chemical computer dna computing optical computer spintronicsbased computer other hardware topics peripheral device inputoutput input mouse keyboard joystick image scanner webcam graphics tablet microphone output monitor printer loudspeaker both floppy disk drive hard disk drive optical disc drive teleprinter computer buses short range rs232 scsi pci usb long range computer networking ethernet atm fddi a general purpose computer has four main components the arithmetic logic unit alu the control unit the memory and the input and output devices collectively termed io these parts are interconnected by buses often made of groups of wires inside each of these parts are thousands to trillions of small electrical circuits which can be turned off or on by means of an electronic switch each circuit represents a bit binary digit of information so that when the circuit is on it represents a 1 and when off it represents a 0 in positive logic representation the circuits are arranged in logic gates so that one or more of the circuits may control the state of one or more of the other circuits input devices when unprocessed data is sent to the computer with the help of input devices the data is processed and sent to output devices the input devices may be handoperated or automated the act of processing is mainly regulated by the cpu some examples of input devices are computer keyboard digital camera digital video graphics tablet image scanner joystick microphone mouse overlay keyboard realtime clock trackball touchscreen output devices the means through which computer gives output are known as output devices some examples of output devices are computer monitor printer pc speaker projector sound card video card control unit cpu design and control unit diagram showing how a particular mips architecture instruction would be decoded by the control system the control unit often called a control system or central controller manages the computers various components it reads and interprets decodes the program instructions transforming them into control signals that activate other parts of the computer control systems in advanced computers may change the order of execution of some instructions to improve performance a key component common to all cpus is the program counter a special memory cell a register that keeps track of which location in memory the next instruction is to be read from the control systems function is as followsnote that this is a simplified description and some of these steps may be performed concurrently or in a different order depending on the type of cpu read the code for the next instruction from the cell indicated by the program counter decode the numerical code for the instruction into a set of commands or signals for each of the other systems increment the program counter so it points to the next instruction read whatever data the instruction requires from cells in memory or perhaps from an input device the location of this required data is typically stored within the instruction code provide the necessary data to an alu or register if the instruction requires an alu or specialized hardware to complete instruct the hardware to perform the requested operation write the result from the alu back to a memory location or to a register or perhaps an output device jump back to step 1 since the program counter is conceptually just another set of memory cells it can be changed by calculations done in the alu adding 100 to the program counter would cause the next instruction to be read from a place 100 locations further down the program instructions that modify the program counter are often known as jumps and allow for loops instructions that are repeated by the computer and often conditional instruction execution both examples of control flow the sequence of operations that the control unit goes through to process an instruction is in itself like a short computer program and indeed in some more complex cpu designs there is another yet smaller computer called a microsequencer which runs a microcode program that causes all of these events to happen central processing unit cpu the control unit alu and registers are collectively known as a central processing unit cpu early cpus were composed of many separate components but since the mid1970s cpus have typically been constructed on a single integrated circuit called a microprocessor arithmetic logic unit alu arithmetic logic unit the alu is capable of performing two classes of operations arithmetic and logic the set of arithmetic operations that a particular alu supports may be limited to addition and subtraction or might include multiplication division trigonometry functions such as sine cosine etc and square roots some can only operate on whole numbers integers while others use floating point to represent real numbers albeit with limited precision however any computer that is capable of performing just the simplest operations can be programmed to break down the more complex operations into simple steps that it can perform therefore any computer can be programmed to perform any arithmetic operationalthough it will take more time to do so if its alu does not directly support the operation an alu may also compare numbers and return boolean truth values true or false depending on whether one is equal to greater than or less than the other is 64 greater than 65 logic operations involve boolean logic and or xor and not these can be useful for creating complicated conditional statements and processing boolean logic superscalar computers may contain multiple alus allowing them to process several instructions simultaneously graphics processors and computers with simd and mimd features often contain alus that can perform arithmetic on vectors and matrices memory computer data storage magnetic core memory was the computer memory of choice throughout the 1960s until it was replaced by semiconductor memory a computers memory can be viewed as a list of cells into which numbers can be placed or read each cell has a numbered address and can store a single number the computer can be instructed to put the number 123 into the cell numbered 1357 or to add the number that is in cell 1357 to the number that is in cell 2468 and put the answer into cell 1595 the information stored in memory may represent practically anything letters numbers even computer instructions can be placed into memory with equal ease since the cpu does not differentiate between different types of information it is the softwares responsibility to give significance to what the memory sees as nothing but a series of numbers in almost all modern computers each memory cell is set up to store binary numbers in groups of eight bits called a byte each byte is able to represent 256 different numbers 28 256 either from 0 to 255 or 128 to 127 to store larger numbers several consecutive bytes may be used typically two four or eight when negative numbers are required they are usually stored in twos complement notation other arrangements are possible but are usually not seen outside of specialized applications or historical contexts a computer can store any kind of information in memory if it can be represented numerically modern computers have billions or even trillions of bytes of memory the cpu contains a special set of memory cells called registers that can be read and written to much more rapidly than the main memory area there are typically between two and one hundred registers depending on the type of cpu registers are used for the most frequently needed data items to avoid having to access main memory every time data is needed as data is constantly being worked on reducing the need to access main memory which is often slow compared to the alu and control units greatly increases the computers speed computer main memory comes in two principal varieties randomaccess memory or ram readonly memory or rom ram can be read and written to anytime the cpu commands it but rom is preloaded with data and software that never changes therefore the cpu can only read from it rom is typically used to store the computers initial startup instructions in general the contents of ram are erased when the power to the computer is turned off but rom retains its data indefinitely in a pc the rom contains a specialized program called the bios that orchestrates loading the computers operating system from the hard disk drive into ram whenever the computer is turned on or reset in embedded computers which frequently do not have disk drives all of the required software may be stored in rom software stored in rom is often called firmware because it is notionally more like hardware than software flash memory blurs the distinction between rom and ram as it retains its data when turned off but is also rewritable it is typically much slower than conventional rom and ram however so its use is restricted to applications where high speed is unnecessary in more sophisticated computers there may be one or more ram cache memories which are slower than registers but faster than main memory generally computers with this sort of cache are designed to move frequently needed data into the cache automatically often without the need for any intervention on the programmers part inputoutput io inputoutput hard disk drives are common storage devices used with computers io is the means by which a computer exchanges information with the outside world on a typical personal computer peripherals include input devices like the keyboard and mouse and output devices such as the display and printer hard disk drives floppy disk drives and optical disc drives serve as both input and output devices computer networking is another form of io io devices are often complex computers in their own right with their own cpu and memory a graphics processing unit might contain fifty or more tiny computers that perform the calculations necessary to display 3d graphics modern desktop computers contain many smaller computers that assist the main cpu in performing io a 2016era flat screen display contains its own computer circuitry multitasking computer multitasking while a computer may be viewed as running one gigantic program stored in its main memory in some systems it is necessary to give the appearance of running several programs simultaneously this is achieved by multitasking ie having the computer switch rapidly between running each program in turn before the era of inexpensive computers the principal use for multitasking was to allow many people to share the same computer seemingly multitasking would cause a computer that is switching between several programs to run more slowly in direct proportion to the number of programs it is running but most programs spend much of their time waiting for slow inputoutput devices to complete their tasks if a program is waiting for the user to click on the mouse or press a key on the keyboard then it will not take a time slice until the event it is waiting for has occurred this frees up time for other programs to execute so that many programs may be run simultaneously without unacceptable speed loss multiprocessing multiprocessing cray designed many supercomputers that used multiprocessing heavily some computers are designed to distribute their work across several cpus in a multiprocessing configuration a technique once employed only in large and powerful machines such as supercomputers mainframe computers and servers multiprocessor and multicore multiple cpus on a single integrated circuit personal and laptop computers are now widely available and are being increasingly used in lowerend markets as a result supercomputers in particular often have highly unique architectures that differ significantly from the basic storedprogram architecture and from general purpose computers they often feature thousands of cpus customized highspeed interconnects and specialized computing hardware such designs tend to be useful only for specialized tasks due to the large scale of program organization required to successfully utilize most of the available resources at once supercomputers usually see usage in largescale simulation graphics rendering and cryptography applications as well as with other socalled embarrassingly parallel tasks software computer software software refers to parts of the computer which do not have a material form such as programs data protocols etc software is that part of a computer system that consists of encoded information or computer instructions in contrast to the physical hardware from which the system is built computer software includes computer programs libraries and related nonexecutable data such as online documentation or digital media it is often divided into system software and application software computer hardware and software require each other and neither can be realistically used on its own when software is stored in hardware that cannot easily be modified such as with bios rom in an ibm pc compatible computer it is sometimes called firmware operating system system software unix and bsd unix system v ibm aix hpux solaris sunos irix list of bsd operating systems gnulinux list of linux distributions comparison of linux distributions microsoft windows windows 95 windows 98 windows nt windows 2000 windows me windows xp windows vista windows 7 windows 8 windows 81 windows 10 dos 86dos qdos ibm pc dos msdos drdos freedos macintosh operating systems classic mac os macos previously os x and mac os x embedded and realtime list of embedded operating systems experimental amoeba oberonbluebottle plan 9 from bell labs library multimedia directx opengl openal vulkan api programming library c standard library standard template library data protocol tcpip kermit ftp http smtp file format html xml jpeg mpeg png user interface graphical user interface wimp microsoft windows gnome kde qnx photon cde gem aqua textbased user interface commandline interface text user interface application software office suite word processing desktop publishing presentation program database management system scheduling time management spreadsheet accounting software internet access browser email client web server mail transfer agent instant messaging design and manufacturing computeraided design computeraided manufacturing plant management robotic manufacturing supply chain management graphics raster graphics editor vector graphics editor 3d modeler animation editor 3d computer graphics video editing image processing audio digital audio editor audio playback mixing audio synthesis computer music software engineering compiler assembler interpreter debugger text editor integrated development environment software performance analysis revision control software configuration management educational edutainment educational game serious game flight simulator games strategy arcade puzzle simulation firstperson shooter platform massively multiplayer interactive fiction misc artificial intelligence antivirus software malware scanner installerpackage management systems file manager languages there are thousands of different programming languagessome intended to be general purpose others useful only for highly specialized applications programming languages lists of programming languages timeline of programming languages list of programming languages by category generational list of programming languages list of programming languages nonenglishbased programming languages commonly used assembly languages arm mips x86 commonly used highlevel programming languages ada basic c c c cobol fortran pl1 rexx java lisp pascal object pascal commonly used scripting languages bourne script javascript python ruby php perl application software programs the defining feature of modern computers which distinguishes them from all other machines is that they can be programmed that is to say that some type of instructions the program can be given to the computer and it will process them modern computers based on the von neumann architecture often have machine code in the form of an imperative programming language in practical terms a computer program may be just a few instructions or extend to many millions of instructions as do the programs for word processors and web browsers for example a typical modern computer can execute billions of instructions per second gigaflops and rarely makes a mistake over many years of operation large computer programs consisting of several million instructions may take teams of programmers years to write and due to the complexity of the task almost certainly contain errors stored program architecture computer program and computer programming replica of the manchester baby the worlds first electronic storedprogram computer at the museum of science and industry in manchester england this section applies to most common ram machinebased computers in most cases computer instructions are simple add one number to another move some data from one location to another send a message to some external device etc these instructions are read from the computers memory and are generally carried out executed in the order they were given however there are usually specialized instructions to tell the computer to jump ahead or backwards to some other place in the program and to carry on executing from there these are called jump instructions or branches furthermore jump instructions may be made to happen conditionally so that different sequences of instructions may be used depending on the result of some previous calculation or some external event many computers directly support subroutines by providing a type of jump that remembers the location it jumped from and another instruction to return to the instruction following that jump instruction program execution might be likened to reading a book while a person will normally read each word and line in sequence they may at times jump back to an earlier place in the text or skip sections that are not of interest similarly a computer may sometimes go back and repeat the instructions in some section of the program over and over again until some internal condition is met this is called the flow of control within the program and it is what allows the computer to perform tasks repeatedly without human intervention comparatively a person using a pocket calculator can perform a basic arithmetic operation such as adding two numbers with just a few button presses but to add together all of the numbers from 1 to 1000 would take thousands of button presses and a lot of time with a near certainty of making a mistake on the other hand a computer may be programmed to do this with just a few simple instructions the following example is written in the mips assembly language begin addi 8 0 0 initialize sum to 0 addi 9 0 1 set first number to add 1 loop slti 10 9 1000 check if the number is less than 1000 beq 10 0 finish if odd number is greater than n then exit add 8 8 9 update sum addi 9 9 1 get next number j loop repeat the summing process finish add 2 8 0 put sum in output register once told to run this program the computer will perform the repetitive addition task without further human intervention it will almost never make a mistake and a modern pc can complete the task in a fraction of a second machine code in most computers individual instructions are stored as machine code with each instruction being given a unique number its operation code or opcode for short the command to add two numbers together would have one opcode the command to multiply them would have a different opcode and so on the simplest computers are able to perform any of a handful of different instructions the more complex computers have several hundred to choose from each with a unique numerical code since the computers memory is able to store numbers it can also store the instruction codes this leads to the important fact that entire programs which are just lists of these instructions can be represented as lists of numbers and can themselves be manipulated inside the computer in the same way as numeric data the fundamental concept of storing programs in the computers memory alongside the data they operate on is the crux of the von neumann or stored program architecture in some cases a computer might store some or all of its program in memory that is kept separate from the data it operates on this is called the harvard architecture after the harvard mark i computer modern von neumann computers display some traits of the harvard architecture in their designs such as in cpu caches while it is possible to write computer programs as long lists of numbers machine language and while this technique was used with many early computers it is extremely tedious and potentially errorprone to do so in practice especially for complicated programs instead each basic instruction can be given a short name that is indicative of its function and easy to remember a mnemonic such as add sub mult or jump these mnemonics are collectively known as a computers assembly language converting programs written in assembly language into something the computer can actually understand machine language is usually done by a computer program called an assembler a 1970s punched card containing one line from a fortran program the card reads z1 y w1 and is labeled proj039 for identification purposes programming language programming language programming languages provide various ways of specifying programs for computers to run unlike natural languages programming languages are designed to permit no ambiguity and to be concise they are purely written languages and are often difficult to read aloud they are generally either translated into machine code by a compiler or an assembler before being run or translated directly at run time by an interpreter sometimes programs are executed by a hybrid method of the two techniques lowlevel languages lowlevel programming language machine languages and the assembly languages that represent them collectively termed lowlevel programming languages tend to be unique to a particular type of computer for instance an arm architecture computer such as may be found in a smartphone or a handheld videogame cannot understand the machine language of an x86 cpu that might be in a pc highlevel languagesthird generation language highlevel programming language although considerably easier than in machine language writing long programs in assembly language is often difficult and is also error prone therefore most practical programs are written in more abstract highlevel programming languages that are able to express the needs of the programmer more conveniently and thereby help reduce programmer error high level languages are usually compiled into machine language or sometimes into assembly language and then into machine language using another computer program called a compiler high level languages are less related to the workings of the target computer than assembly language and more related to the language and structure of the problems to be solved by the final program it is therefore often possible to use different compilers to translate the same high level language program into the machine language of many different types of computer this is part of the means by which software like video games may be made available for different computer architectures such as personal computers and various video game consoles fourthgeneration languages fourthgeneration programming language fourthgeneration languages 4gl are less procedural than 3g languages the benefit of 4gl is that they provide ways to obtain information without requiring the direct help of a programmer program design this section does not cite any sources please help improve this section by adding citations to reliable sources unsourced material may be challenged and removed july 2012 learn how and when to remove this template message program design of small programs is relatively simple and involves the analysis of the problem collection of inputs using the programming constructs within languages devising or using established procedures and algorithms providing data for output devices and solutions to the problem as applicable as problems become larger and more complex features such as subprograms modules formal documentation and new paradigms such as objectoriented programming are encountered large programs involving thousands of line of code and more require formal software methodologies the task of developing large software systems presents a significant intellectual challenge producing software with an acceptably high reliability within a predictable schedule and budget has historically been difficult the academic and professional discipline of software engineering concentrates specifically on this challenge bugs software bug the actual first computer bug a moth found trapped on a relay of the harvard mark ii computer errors in computer programs are called bugs they may be benign and not affect the usefulness of the program or have only subtle effects but in some cases they may cause the program or the entire system to hang becoming unresponsive to input such as mouse clicks or keystrokes to completely fail or to crash otherwise benign bugs may sometimes be harnessed for malicious intent by an unscrupulous user writing an exploit code designed to take advantage of a bug and disrupt a computers proper execution bugs are usually not the fault of the computer since computers merely execute the instructions they are given bugs are nearly always the result of programmer error or an oversight made in the programs design admiral grace hopper an american computer scientist and developer of the first compiler is credited for having first used the term bugs in computing after a dead moth was found shorting a relay in the harvard mark ii computer in september 1947 firmware firmware is the technology which has the combination of both hardware and software such as bios chip inside a computer this chip hardware is located on the motherboard and has the bios set up software stored in it networking and the internet computer networking and internet visualization of a portion of the routes on the internet computers have been used to coordinate information between multiple locations since the 1950s the us militarys sage system was the first largescale example of such a system which led to a number of specialpurpose commercial systems such as sabre the technologies that made the arpanet possible spread and evolved in time the network spread beyond academic and military institutions and became known as the internet the emergence of networking involved a redefinition of the nature and boundaries of the computer computer operating systems and applications were modified to include the ability to define and access the resources of other computers on the network such as peripheral devices stored information and the like as extensions of the resources of an individual computer initially these facilities were available primarily to people working in hightech environments but in the 1990s the spread of applications like email and the world wide web combined with the development of cheap fast networking technologies like ethernet and adsl saw computer networking become almost ubiquitous in fact the number of computers that are networked is growing phenomenally a very large proportion of personal computers regularly connect to the internet to communicate and receive information wireless networking often utilizing mobile phone networks has meant networking is becoming increasingly ubiquitous even in mobile computing environments unconventional computers human computer see also harvard computers a computer does not need to be electronic nor even have a processor nor ram nor even a hard disk while popular usage of the word computer is synonymous with a personal electronic computer the modern unconventional computing further information unconventional computing historically computers evolved from mechanical computers and eventually from vacuum tubes to transistors however conceptually computational systems as flexible as a personal computer can be built out of almost anything for example a computer can be made out of billiard balls billiard ball computer an often quoted example more realistically modern computers are made out of transistors made of photolithographed semiconductors future there is active research to make computers out of many promising new types of technology such as optical computers dna computers neural computers and quantum computers most computers are universal and are able to calculate any computable function and are limited only by their memory capacity and operating speed however different designs of computers can give very different performance for particular problems for example quantum computers can potentially break some modern encryption algorithms by quantum factoring very quickly computer architecture paradigms there are many types of computer architectures quantum computer vs chemical computer scalar processor vs vector processor nonuniform memory access numa computers register machine vs stack machine harvard architecture vs von neumann architecture cellular architecture of all these abstract machines a quantum computer holds the most promise for revolutionizing computing logic gates are a common abstraction which can apply to most of the above digital or analog paradigms the ability to store and execute lists of instructions called programs makes computers extremely versatile distinguishing them from calculators the churchturing thesis is a mathematical statement of this versatility any computer with a minimum capability being turingcomplete is in principle capable of performing the same tasks that any other computer can perform therefore any type of computer netbook supercomputer cellular automaton etc is able to perform the same computational tasks given enough time and storage capacity artificial intelligence a computer will solve problems in exactly the way it is programmed to without regard to efficiency alternative solutions possible shortcuts or possible errors in the code computer programs that learn and adapt are part of the emerging field of artificial intelligence and machine learning artificial intelligence based products generally fall into two major categories rule based systems and pattern recognition systems rule based systems attempt to represent the rules used by human experts and tend to be expensive to develop pattern based systems use data about a problem to generate conclusions examples of pattern based systems include voice recognition font recognition translation and the emerging field of online marketing professions and organizations as the use of computers has spread throughout society there are an increasing number of careers involving computers computerrelated professions hardwarerelated electrical engineering electronic engineering computer engineering telecommunications engineering optical engineering nanoengineering softwarerelated computer science computer engineering desktop publishing humancomputer interaction information technology information systems computational science software engineering video game industry web design the need for computers to work well together and to be able to exchange information has spawned the need for many standards organizations clubs and societies of both a formal and informal nature organizations standards groups ansi iec ieee ietf iso w3c professional societies acm ais iet ifip bcs freeopen source software groups free software foundation mozilla foundation apache software foundation information technology portal glossary of computers computability theory computer insecurity computer security glossary of computer hardware terms history of computer science list of computer term etymologies list of fictional computers list of pioneers in computer science pulse computation top500 list of most powerful computers notes evans claire l 2018 broad band the untold story of the women who made the internet new york portfoliopenguin isbn9780735211759 fuegi j francis j 2003 lovelace babbage and the creation of the 1843 notes ieee annals of the history of computing 25 4 16 doi101109mahc20031253887 a kempf karl 1961 historical monograph electronic computers within the ordnance corps aberdeen proving ground united states army a phillips tony 2000 the antikythera mechanism i american mathematical society retrieved 5 april 2006 a shannon claude elwood 1940 a symbolic analysis of relay and switching circuits massachusetts institute of technology hdl1721111173 digital equipment corporation 1972 pdp1140 processor handbook pdf maynard ma digital equipment corporation verma g mielke n 1988 reliability performance of etox based flash memories ieee international reliability physics symposium swade doron d february 1993 redeeming charles babbages mechanical computer scientific american 268 2 89 jstor24941379 meuer hans strohmaier erich simon horst dongarra jack 13 november 2006 architectures share over time top500 archived from the original on 20 february 2007 retrieved 27 november 2006 lavington simon 1998 a history of manchester computers 2 ed swindon the british computer society isbn9780902505018 light jennifer s 1999 when computers were women technology and culture 40 3 455483 jstor25147356 registration required help stokes jon 2007 inside the machine an illustrated introduction to microprocessors and computer architecture san francisco no starch press isbn9781593271046 zuse konrad 1993 the computer my life berlin pringlerverlag isbn0387564535 felt dorr e 1916 mechanical arithmetic or the history of the counting machine chicago washington institute ifrah georges 2001 the universal history of computing from the abacus to the quantum computer new york john wiley sons isbn0471396710 berkeley edmund 1949 giant brains or machines that think john wiley sons cohen bernard 2000 howard aiken portrait of a computer pioneer cambridge massachusetts the mit press isbn9780262531795 ligonnire robert 1987 prhistoire et histoire des ordinateurs paris robert laffont isbn9782221052617 couffignal louis 1933 les machines calculer leurs principes leur volution paris gauthiervillars essinger james 2004 jacquards web how a hand loom led to the birth of the information age oxford university press isbn0192805770 hyman anthony 1985 charles babbage pioneer of the computer princeton university press isbn9780691023779 cohen bernard 2000 howard aiken portrait of a computer pioneer cambridge massachusetts the mit press isbn9780262531795 bowden b v 1953 faster than thought new york toronto london pitman publishing corporation moseley maboth 1964 irascible genius charles babbage inventor london hutchinson collier bruce 1970 the little engine that couldve the calculating machines of charles babbage garland publishing inc isbn0824000439 randell brian 1982 from analytical engine to electronic digital computer the contributions of ludgate torres and bush pdf archived from the original pdf on 21 september 2013 retrieved 29 october 2013 smith erika e 2013 recognizing a collective inheritance through the history of women in computing clcweb comparative literature culture a wwweb journal 15 1 19 via ebscohost subscription required help media related to computers at wikimedia commons wikiversity has a quiz on this article warhol the computer authority control bnf cb119401913 data gnd 40700835 lccn sh85029552 nara 10636641 ndl 00561435 vtebasic computer componentsinput devices keyboard image scanner microphone pointing device graphics tablet joystick light pen mouse optical pointing stick touchpad touchscreen trackball refreshable braille display sound card webcam softcam video card output devices monitor refreshable braille display printer speakers plotter sound card video card removable data storage optical disc cd dvd bluray disk pack floppy disk memory card usb flash drive computer case central processing unit cpu hdd ssd sshd motherboard network interface controller power supply randomaccess memory ram fax modem expansion card ports ethernet firewire ieee 1394 parallel port serial port ps2 port usb thunderbolt displayport hdmi dvi vga esata audio jack vtedigital electronicscomponents combinational logic sequential logic integrated circuit ic logic gate theory digital signal boolean algebra logic synthesis logic in computer science computer architecture digital signal digital signal processing circuit minimization switching circuit theory design logic synthesis place and route placement routing registertransfer level hardware description language highlevel synthesis formal equivalence checking synchronous logic asynchronous logic finitestate machine hierarchical state machine applications computer 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