Computers and computing devices from different erasA computer is a machine that can be instructed to carry out of or operations automatically via. Modern computers have the ability to follow generalized sets of operations, called.
These programs enable computers to perform an extremely wide range of tasks. A 'complete' computer including the, the (main ), and equipment required and used for 'full' operation can be referred to as a computer system. This term may as well be used for a group of computers that are connected and work together, in particular a or.Computers are used as for a wide variety of. This includes simple special purpose devices like and, factory devices such as and, and also general purpose devices like and such as. The is run on computers and it connects hundreds of millions of other computers and their users.Early computers were only conceived as calculating devices.
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Since ancient times, simple manual devices like the aided people in doing calculations. Early in the, some mechanical devices were built to automate long tedious tasks, such as guiding patterns for.
More sophisticated electrical did specialized calculations in the early 20th century. The first electronic calculating machines were developed during. The first in the late 1940s were followed by the and in the late 1950s, leading to the and the in the 1970s. The speed, power and versatility of computers have been increasing dramatically ever since then, with increasing at a rapid pace, as predicted by.Conventionally, a modern computer consists of at least one, typically a (CPU), and some form of. 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. Devices include input devices (keyboards, mice, joystick, etc.), output devices (monitor screens, printers, etc.), and input/output devices that perform both functions (e.g., the 2000s-era ). Allow information to be retrieved from an external source and they enable the result of operations to be saved and retrieved.
A female computer, with microscope and calculator, 1952According 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 sic read the truest computer of Times, and the best Arithmetician that euer sic breathed, and he reduceth thy dayes into a short number.' This usage of the term referred to a, a person who carried out calculations or computations. The word continued with the same meaning until the middle of the 20th century. During the latter part of this period women were often hired as computers because they could be paid less than their male counterparts. By 1943, most human computers were women.The Online Etymology Dictionary gives the first attested use of 'computer' in the 1640s, meaning 'one who calculates'; this is an 'agent noun from compute (v.)'. The Online Etymology Dictionary states that the use of the term to mean 'calculating machine' (of any type) is from 1897.'
The Online Etymology Dictionary indicates that the 'modern use' of the term, to mean 'programmable digital electronic computer' dates from '1945 under this name; in a theoretical sense from 1937, as '. The, dating back to circa 150–100 BC, is an early mechanical.The is believed to be the earliest mechanical, according to. It was designed to calculate astronomical positions. It was discovered in 1901 in the off the Greek island of, between and, and has been dated to c. 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 was a invented by Abū Rayhān al-Bīrūnī in the early 11th century. The was invented in the in either the 1st or 2nd centuries BC and is often attributed to. A combination of the planisphere and, the astrolabe was effectively an analog computer capable of working out several different kinds of problems in.
An astrolabe incorporating a mechanical computer and -wheels was invented by Abi Bakr of, in 1235. Invented the first mechanical geared astrolabe, an early fixed- knowledge processing with a and gear-wheels, c. 1000 AD.The, 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 was a manual instrument to calculate the area of a closed figure by tracing over it with a mechanical linkage. A portion of., an English mechanical engineer and, originated the concept of a programmable computer. Considered the ', he conceptualized and invented the first in the early 19th century. After working on his revolutionary, designed to aid in navigational calculations, in 1833 he realized that a much more general design, an, was possible. The input of programs and data was to be provided to the machine via, a method being used at the time to direct mechanical such as the.
For output, the machine would have a printer, a curve plotter and a bell. The machine would also be able to punch numbers onto cards to be read in later. The Engine incorporated an, in the form of and, and integrated, making it the first design for a general-purpose computer that could be described in modern terms as.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 to cease funding. Babbage's failure to complete the analytical engine can be chiefly attributed to political and financial difficulties as well as 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 engine's computing unit (the mill) in 1888. He gave a successful demonstration of its use in computing tables in 1906.Analog computers. 's third tide-predicting machine design, 1879–81During the first half of the 20th century, many scientific needs were met by increasingly sophisticated, which used a direct mechanical or electrical model of the problem as a basis for. However, these were not programmable and generally lacked the versatility and accuracy of modern digital computers. The first modern analog computer was a, invented by in 1872. The, a mechanical analog computer designed to solve differential equations by integration using wheel-and-disc mechanisms, was conceptualized in 1876 by, the brother of the more famous Lord Kelvin.The art of mechanical analog computing reached its zenith with the, built by H. Hazen and at starting in 1927.
This built on the mechanical integrators of and the torque amplifiers invented by H. 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 and aircraft.Digital computers. Replica of 's, 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 all-electric computers, originally using. The, created by German engineer in 1939, was one of the earliest examples of an electromechanical relay computer.In 1941, Zuse followed his earlier machine up with the, the world's first working, fully automatic digital computer.
The Z3 was built with 2000, implementing a 22 that operated at a of about 5–10. Program code was supplied on punched while data could be stored in 64 words of memory or supplied from the keyboard. It was quite similar to modern machines in some respects, pioneering numerous advances such as.
Rather than the harder-to-implement decimal system (used in 's earlier design), using a system meant that Zuse's machines were easier to build and potentially more reliable, given the technologies available at that time. Vacuum tubes and digital electronic circuitsPurely elements soon replaced their mechanical and electromechanical equivalents, at the same time that digital calculation replaced analog. The engineer, working at the in in the 1930s, began to explore the possible use of electronics for the. Experimental equipment that he built in 1934 went into operation five years later, converting a portion of the network into an electronic data processing system, using thousands of. In the US, and of Iowa State University developed and tested the (ABC) in 1942, the first 'automatic electronic digital computer'.
This design was also all-electronic and used about 300 vacuum tubes, with capacitors fixed in a mechanically rotating drum for memory. The first computing device, was used to break German ciphers during World War II.During World War II, the British at achieved a number of successes at breaking encrypted German military communications. The German encryption machine, was first attacked with the help of the electro-mechanical which were often run by women. To crack the more sophisticated German machine, used for high-level Army communications, and his colleagues commissioned Flowers to build the. He spent eleven months from early February 1943 designing and building the first Colossus. After a functional test in December 1943, Colossus was shipped to Bletchley Park, where it was delivered on 18 January 1944 and attacked its first message on 5 February.Colossus was the world's first computer.
It used a large number of valves (vacuum tubes). It had paper-tape input and was capable of being configured to perform a variety of operations on its data, but it was not. Nine Mk II Colossi were built (The Mk I was converted to a Mk II making ten machines in total).
Colossus Mark I contained 1,500 thermionic valves (tubes), but Mark II with 2,400 valves, was both 5 times faster and simpler to operate than Mark I, greatly speeding the decoding process. Was the first electronic, Turing-complete device, and performed ballistics trajectory calculations for the.The (Electronic Numerical Integrator and Computer) was the first electronic programmable computer built in the U.S. Although the ENIAC was similar to the Colossus, it was much faster, more flexible, and it was. Like the Colossus, a 'program' on the ENIAC was defined by the states of its patch cables and switches, a far cry from the electronic machines that came later. Once a program was written, it had to be mechanically set into the machine with manual resetting of plugs and switches. The programmers of the ENIAC were six women, often known collectively as the 'ENIAC girls'.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 and at the University of Pennsylvania, ENIAC's 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 18,000 vacuum tubes, 1,500 relays, and hundreds of thousands of resistors, capacitors, and inductors. Modern computers Concept of modern computerThe principle of the modern computer was proposed by in his seminal 1936 paper, On Computable Numbers. Turing proposed a simple device that he called 'Universal Computing machine' and that is now known as a. He proved that such a machine is capable of computing anything that is computable by executing instructions (program) stored on tape, allowing the machine to be programmable.
The fundamental concept of Turing's design is the, where all the instructions for computing are stored in memory. Acknowledged that the central concept of the modern computer was due to this paper. Turing machines are to this day a central object of study in.
Except for the limitations imposed by their finite memory stores, modern computers are said to be, which is to say, they have execution capability equivalent to a universal Turing machine.Stored programs. A section of the, the first electronic.Early computing machines had fixed programs. Changing its function required the re-wiring and re-structuring of the machine. With the proposal of the stored-program computer this changed. A stored-program computer includes by design an and can store in memory a set of instructions (a ) that details the. The theoretical basis for the stored-program computer was laid by in his 1936 paper. In 1945, Turing joined the and began work on developing an electronic stored-program digital computer.
His 1945 report 'Proposed Electronic Calculator' was the first specification for such a device. John von Neumann at the also circulated his in 1945.The was the world's first.
It was built at the by, and, and ran its first program on 21 June 1948. It was designed as a for the, the first digital storage device.
Although the computer was considered 'small and primitive' by the standards of its time, it was the first working machine to contain all of the elements essential to a modern electronic computer. As soon as the Baby had demonstrated the feasibility of its design, a project was initiated at the university to develop it into a more usable computer, the. Was the first person to develop a for programming language.The Mark 1 in turn quickly became the prototype for the, the world's first commercially available general-purpose computer. Built by, it was delivered to the in February 1951. At least seven of these later machines were delivered between 1953 and 1957, one of them to labs in.
In October 1947, the directors of British catering company decided to take an active role in promoting the commercial development of computers. The computer became operational in April 1951 and ran the world's first regular routine office computer.Transistors. A.The concept of a was proposed by in 1925., and at invented the first practical transistor, the, in 1947, followed by the in 1948. From 1955 onwards, transistors replaced 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. 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.
However, early junction transistors were relatively bulky devices that were difficult to manufacture on a basis, which limited them to a number of specialised applications.At the, a team under the leadership of designed and built a machine using the newly developed instead of valves. Their first and the first in the world, was, and a second version was completed there in April 1955. However, the machine did make use of valves to generate its 125 kHz clock waveforms and in the circuitry to read and write on its magnetic, so it was not the first completely transistorized computer. That distinction goes to the of 1955, built by the electronics division of the at. Showing (G), body (B), source (S) and drain (D) terminals.
The gate is separated from the body by an insulating layer (pink).The (MOSFET), also known as the MOS transistor, was invented by and at Bell Labs in 1959. It was the first truly compact transistor that could be miniaturised and mass-produced for a wide range of uses.
With its, and much lower power consumption and higher density than bipolar junction transistors, the MOSFET made it possible to build. The MOSFET later led to the, and became the driving force behind the. The MOSFET is the most widely used transistor in computers, and is the fundamental building block of. Integrated circuits.
Further information: andThe next great advance in computing power came with the advent of the (IC).The idea of the integrated circuit was first conceived by a radar scientist working for the of the,. Dummer presented the first public description of an integrated circuit at the Symposium on Progress in Quality Electronic Components in on 7 May 1952.The first working ICs were invented by at and at. Kilby recorded his initial ideas concerning the integrated circuit in July 1958, successfully demonstrating the first working integrated example on 12 September 1958. In his patent application of 6 February 1959, Kilby described his new device as 'a body of semiconductor material. Wherein all the components of the electronic circuit are completely integrated'. However, Kilby's invention was a (hybrid IC), rather than a (IC) chip.
Kilby's IC had external wire connections, which made it difficult to mass-produce.Noyce also came up with his own idea of an integrated circuit half a year later than Kilby. Noyce's invention was the first true monolithic IC chip. His chip solved many practical problems that Kilby's had not. Produced at Fairchild Semiconductor, it was made of, whereas Kilby's chip was made of. Noyce's monolithic IC was using the, developed in early 1959 by his colleague, who in turn incorporated the and processes developed by at during the late 1950s.Modern monolithic ICs are predominantly MOS integrated circuits, built from (MOS transistors). After the first MOSFET was invented by Mohamed Atalla and at Bell Labs in 1959, Atalla first proposed the concept of the MOS integrated circuit in 1960, followed by Kahng in 1961, both noting that the MOS transistor's ease of made it useful for integrated circuits.
The earliest experimental MOS IC to be fabricated was a 16-transistor chip built by Fred Heiman and Steven Hofstein at in 1962. Later introduced the first commercial MOS IC in 1964, developed by Robert Norman. Following the development of the (silicon-gate) MOS transistor by Robert Kerwin, Donald Klein and John Sarace at Bell Labs in 1967, the first MOS IC with was developed by at Fairchild Semiconductor in 1968. The MOSFET has since become the most critical device component in modern ICs.The development of the MOS integrated circuit led to the invention of the, and heralded an explosion in the commercial and personal use of computers. 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 single-chip microprocessor was the, designed and realized by Federico Faggin with his silicon-gate MOS IC technology, along with, and at.
In the early 1970s, MOS IC technology enabled the of more than 10,000 transistors on a single chip.(SoCs) are complete computers on a (or chip) the size of a coin. They may or may not have integrated. If not integrated, The RAM is usually placed directly above (known as ) or below (on the opposite side of the ) the SoC, and the flash memory is usually placed right next to the SoC, this all done to improve data transfer speeds, as the data signals don't have to travel long distances.
Since ENIAC in 1945, computers have advanced enormously, with modern SoCs being the size of a coin while also being hundreds of thousands of times more powerful than ENIAC, integrating billions of transistors, and consuming only a few watts of power.Mobile computersThe first were heavy and ran from mains power. The 50lb was an early example. Later portables such as the and were considerably lighter but still needed to be plugged in. The first, such as the, 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 mobile phones by the early 2000s.These and run on a variety of operating systems and recently became the dominant computing device on the market. These are powered by (SoCs), which are complete computers on a microchip the size of a coin. TypesComputers can be classified in a number of different ways, including:By architecture.By size and form-factor.Hardware. Diagram showing how a particular instruction would be decoded by the control systemThe control unit (often called a control system or central controller) manages the computer's various components; it reads and interprets (decodes) the program instructions, transforming them into control signals that activate other parts of the computer. Main article: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, functions such as sine, cosine, etc.,.
Some can only operate on whole numbers while others use to represent, 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 operation—although 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 (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:,. These can be useful for creating complicated and processing.computers may contain multiple ALUs, allowing them to process several instructions simultaneously. And computers with and features often contain ALUs that can perform arithmetic on and.Memory. Was the computer memory of choice throughout the 1960s, until it was replaced by.A computer's 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 software's 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 in groups of eight bits (called a ). Each byte is able to represent 256 different numbers (2 8 = 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 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 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 computer's speed.Computer main memory comes in two principal varieties:. or RAM. or ROMRAM 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 computer's initial start-up 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 that orchestrates loading the computer's from the hard disk drive into RAM whenever the computer is turned on or reset. In, which frequently do not have disk drives, all of the required software may be stored in ROM.
Software stored in ROM is often called, because it is notionally more like hardware than software. 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, 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 programmer's part.Input/output (I/O). Are common storage devices used with computers.I/O is the means by which a computer exchanges information with the outside world. Devices that provide input or output to the computer are called.
On a typical personal computer, peripherals include input devices like the keyboard and, and output devices such as the and., drives and serve as both input and output devices. Is another form of I/O.I/O devices are often complex computers in their own right, with their own CPU and memory. A might contain fifty or more tiny computers that perform the calculations necessary to display. Modern contain many smaller computers that assist the main CPU in performing I/O.
A 2016-era flat screen display contains its own computer circuitry.Multitasking. Main article: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 i.e.
Having the computer switch rapidly between running each program in turn. One means by which this is done is with a special signal called an, which can periodically cause the computer to stop executing instructions where it was and do something else instead.
By remembering where it was executing prior to the interrupt, the computer can return to that task later. If several programs are running 'at the same time'. Then the interrupt generator might be causing several hundred interrupts per second, causing a program switch each time. Since modern computers typically execute instructions several orders of magnitude faster than human perception, it may appear that many programs are running at the same time even though only one is ever executing in any given instant. This method of multitasking is sometimes termed 'time-sharing' since each program is allocated a 'slice' of time 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 input/output 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. 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,. Multiprocessor and (multiple CPUs on a single integrated circuit) personal and laptop computers are now widely available, and are being increasingly used in lower-end markets as a result.Supercomputers in particular often have highly unique architectures that differ significantly from the basic stored-program architecture and from general purpose computers. They often feature thousands of CPUs, customized high-speed 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 large-scale, and applications, as well as with other so-called ' tasks.Software.
Main article: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 from which the system is built. Computer software includes, and related non-executable, such as.
It is often divided into and Computer hardware and software require each other and neither can be realistically used on its own. Replica of the, the world's first electronic, at the in Manchester, EnglandThis section applies to most common –based 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 computer's and are generally carried out 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 ). Furthermore, jump instructions may be made to happen 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 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 within the program and it is what allows the computer to perform tasks repeatedly without human intervention.Comparatively, a person using a pocket 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 1,000 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.
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 registerOnce 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 codeIn most computers, individual instructions are stored as with each instruction being given a unique number (its operation code or 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 computer's 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 computer's 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 after the computer. Modern von Neumann computers display some traits of the Harvard architecture in their designs, such as in.While it is possible to write computer programs as long lists of numbers and while this technique was used with many early computers, it is extremely tedious and potentially error-prone 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 such as ADD, SUB, MULT or JUMP.
These mnemonics are collectively known as a computer's. 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. Main article: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 that are able to express the needs of the 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. 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 problem(s) 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.Program design. This section does not any. Unsourced material may be challenged. ( July 2012) 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 object-oriented programming are encountered. Large programs involving thousands of line of code and more require formal software methodologies.The task of developing large 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 concentrates specifically on this challenge.Bugs. The actual first computer bug, a moth found trapped on a relay of the Harvard Mark II computerErrors in computer programs are called '.
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 ', becoming unresponsive to input such as clicks or keystrokes, to completely fail, or to. Otherwise benign bugs may sometimes be harnessed for malicious intent by an unscrupulous user writing an, code designed to take advantage of a bug and disrupt a computer's 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 program's design.Admiral, an American computer scientist and developer of the first, is credited for having first used the term 'bugs' in computing after a dead moth was found shorting a relay in the computer in September 1947. Networking and the Internet. Visualization of a portion of the on the InternetComputers have been used to coordinate information between multiple locations since the 1950s.
Military's system was the first large-scale example of such a system, which led to a number of special-purpose commercial systems such as. In the 1970s, computer engineers at research institutions throughout the United States began to link their computers together using telecommunications technology.
The effort was funded by ARPA (now ), and the that resulted was called the. 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 high-tech environments, but in the 1990s the spread of applications like e-mail and the, combined with the development of cheap, fast networking technologies like and 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. See also:A computer does not need to be, nor even have a, nor, nor even a. While popular usage of the word 'computer' is synonymous with a personal electronic computer, the modern definition of a computer is literally: ' A device that computes, especially a programmable usually electronic machine that performs high-speed mathematical or logical operations or that assembles, stores, correlates, or otherwise processes information.' Any device which processes information qualifies as a computer, especially if the processing is purposeful. FutureThere is active research to make computers out of many promising new types of technology, such as,. Most computers are universal, and are able to calculate any, 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 ) very quickly.Computer architecture paradigmsThere are many types of:. vs. vs.
(NUMA) computers. vs. vs.Of all these, a quantum computer holds the most promise for revolutionizing computing. Are a common abstraction which can apply to most of the above or paradigms. The ability to store and execute lists of instructions called makes computers extremely versatile, distinguishing them from.
The is a mathematical statement of this versatility: any computer with a is, in principle, capable of performing the same tasks that any other computer can perform. Therefore, any type of computer (, etc.) is able to perform the same computational tasks, given enough time and storage capacity.Artificial intelligenceA 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 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 on-line marketing.Professions and organizationsAs the use of computers has spread throughout society, there are an increasing number of careers involving computers.Hardware-related,Software-related,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.Standards groups,Professional societies,/ groups,See also.