A Brief History of Computing

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Unfortunately these are in Latin, but they are here at the Royal Society so if you want to know more, and have your Latin knowledge at the ready, do please come and have a look. In our collections we have a number of papers where Babbage or his contemporaries refer to this machine. Finally we reach the twentieth century. Professor Wilkes built up a lengthy list of achievements but the one that stands out to me is that he is credited with constructing the first operational machine that could store programmes alongside data, known as the electronic delay storage automatic calculator ESDAC , a name which will undoubtedly mean more to some people than others.

These developments were not done in isolation and computer scientists worked on similar projects at the University of Manchester and of course work was also being done internationally. Welcome to The Repository , the Royal Society's history of science blog. Subscribe to RSS. Subscribe by email. 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 system's function is as follows—note 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:.

Since the program counter is conceptually just another set of memory cells, it can be changed by calculations done in the ALU. Adding to the program counter would cause the next instruction to be read from a place 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.

Early CPUs were composed of many separate components but since the mids CPUs have typically been constructed on a single integrated circuit called a microprocessor. The ALU is capable of performing two classes of operations: arithmetic and logic. 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.


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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 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?

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. 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 into the cell numbered " or to "add the number that is in cell to the number that is in cell and put the answer into cell 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 binary numbers in groups of eight bits called a byte. 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 two's 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.

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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 computer's speed. 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 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 programmer's part. Hard disk drives , floppy disk drives and optical disc drives serve as both input and output devices. A graphics processing unit might contain fifty or more tiny computers that perform the calculations necessary to display 3D graphics. A era flat screen display contains its own computer circuitry.

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. 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". 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. 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. 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 multi-core 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.

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 simulation , graphics rendering , and cryptography applications, as well as with other so-called " embarrassingly parallel " tasks. 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 non-executable 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. There are thousands of different programming languages—some intended to be general purpose, others useful only for highly specialized applications.

The defining feature of modern computers which distinguishes them from all other machines is that they can be programmed.

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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. This section applies to most common RAM machine —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 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 1, 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 :.

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. 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 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 [ citation needed ] , 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 error-prone to do so in practice, especially for complicated programs.

These mnemonics are collectively known as a computer's 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. 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. Machine languages and the assembly languages that represent them collectively termed low-level 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 hand-held videogame cannot understand the machine language of an x86 CPU that might be in a PC.


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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 high-level 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.

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.

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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. 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 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.

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 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. Computers have been used to coordinate information between multiple locations since the s.

The U. 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 s the spread of applications like e-mail 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.

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 [] 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. 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. There are many types of computer architectures :. Of all these abstract machines , a quantum computer holds the most promise for revolutionizing computing.

The ability to store and execute lists of instructions called programs makes computers extremely versatile, distinguishing them from calculators. The Church—Turing thesis is a mathematical statement of this versatility: any computer with a minimum capability being Turing-complete 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. 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 on-line marketing. As the use of computers has spread throughout society, there are an increasing number of careers involving computers. 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.

From Wikipedia, the free encyclopedia. For other uses, see Computer disambiguation. Automatic general-purpose device for performing arithmetic or logical operations. Main article: History of computing hardware. Main article: Analog computer. It has been suggested that this section be split out into another article titled Digital computer.

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Discuss May Main article: Stored-program computer. Main articles: Transistor and History of the transistor. Main articles: Integrated circuit and Invention of the integrated circuit. Further information: Planar process and Microprocessor. Main articles: Computer hardware , Personal computer hardware , Central processing unit , and Microprocessor.

Play media. Main articles: CPU design and Control unit. Main article: Arithmetic logic unit. Main article: Computer data storage. Main article: Computer multitasking. Main article: Multiprocessing. Main article: Computer software. Main articles: Computer program and Computer programming. Main article: Programming language. Main article: Low-level programming language. Main article: High-level programming language. 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 Learn how and when to remove this template message. Main article: Software bug. Main articles: Computer networking and Internet. Main article: Human computer. See also: Harvard Computers. 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 TOP list of most powerful computers Unconventional computing.

Online Etymology Dictionary. The containers thus served as something of a bill of lading or an accounts book. In order to avoid breaking open the containers, first, clay impressions of the tokens were placed on the outside of the containers, for the count; the shapes of the impressions were abstracted into stylized marks; finally, the abstract marks were systematically used as numerals; these numerals were finally formalized as numbers. Eventually Schmandt-Besserat estimates it took years Archived 30 January at the Wayback Machine the marks on the outside of the containers were all that were needed to convey the count, and the clay containers evolved into clay tablets with marks for the count.

Retrieved 1 July Wiet, V. Elisseeff, P. Wolff, J. Naudu Bibcode : Natur. Transactions of the American Philosophical Society. IEEE Micro. Turk J Elec Engin. Charles Babbage, Father of the Computer. Crowell-Collier Press.

A Brief History of Computing

Online stuff. Science Museum. Retrieved 1 August New Scientist. Stanford Encyclopedia of Philosophy. The Life and Work of Konrad Zuse. EPE Online. Archived from the original on 1 June Retrieved 17 June The New York Times. Der Computer. Mein Lebenswerk in German 3rd ed. Berlin: Springer-Verlag. The Story of IT: Zuse". Archived from the original on 18 September Retrieved 1 June Burks The First Electronic Computer. BBC News. Retrieved 14 October The National Museum of Computing.

Archived from the original on 18 April Retrieved 7 January Sperry Rand. Proceedings of the London Mathematical Society. British Computer Society. Retrieved 10 January Cambridge University Press. Nanoelectronics: Materials, Devices, Applications, 2 Volumes. Introduction to Transistor Circuits. Edinburgh: Oliver and Boyd. The Silicon Engine. Computer History Museum. History of Semiconductor Engineering. Proceedings of the IEEE. Retrieved 18 July Retrieved 20 July Scientific American.

Bibcode : SciAm. American Chemical Society. United States Patent and Trademark Office. National Inventors Hall of Fame. Retrieved 27 June Retrieved 21 June Retrieved 21 July World Scientific. Retrieved 13 August Johns Hopkins University Press. Electrochemical Society. The Electrochemical Society Interface. Retrieved 22 July Ars Technica. Archived from the original on 26 June All of the architectures listed in this table, except for Alpha, existed in bit forms before their bit incarnations were introduced.

Although the control unit is solely responsible for instruction interpretation in most modern computers, this is not always the case. Some computers have instructions that are partially interpreted by the control unit with further interpretation performed by another device. For example, EDVAC , one of the earliest stored-program computers, used a central control unit that only interpreted four instructions. All of the arithmetic-related instructions were passed on to its arithmetic unit and further decoded there. Eck A K Peters, Ltd. Handbook of Parallel Computing and Statistics.

CRC Press. Introduction to the Basic Computer. Porat Introduction to Microcomputers and the Microprocessors. Davis Noise Reduction in Speech Applications. These so-called computer clusters can often provide supercomputer performance at a much lower cost than customized designs. While custom architectures are still used for most of the most powerful supercomputers, there has been a proliferation of cluster computers in recent years. However, this method was usually used only as part of the booting process.