Sunday, October 11, 2015

CHARACTERISTICS OF COMPUTERS

              CHARACTERISTICS OF COMPUTERS



Basic Concepts of Computer

Computer is an electronic device which is used to store the data, as per given instructions it gives results quickly and accurately.
  • Data : Data is a raw material of information.
  • Information : Proper collection of the data is called information.
Characteristics of Computer
  • SPEED : In general, no human being can compete to solving the complex computation, faster than computer.
  • ACCURACY : Since Computer is programmed, so what ever input we give it gives result with accuratly.
  • STORAGE : Computer can store mass storage of data with appropriate formate.
  • DILIGENCE : Computer can work for hours without any break and creating error.
  • VERSATILITY : We can use computer to perform completely different type of work at the same time.
  • POWER OF REMEMBERING : It can remember data for us.
  • NO IQ : Computer does not work without instruction.
  • NO FEELING : Computer does not have emotions, knowledge, experience, feeling.
Computer and its components
Computer : Computer itself a combination of different type of separate electronic device. i.e. Computer only will be computer if it has INPUT DEVICE, PROCESS UNIT, and OUTPUT DEVICE.
  • Central Processing Unit (CPU) : It is heart and mind of the computer without this unit computer unable to process.
  • Keyboard : This is an input device which is used to input the data into the computer.
  • Mouse : This is also an input device which is used to input the data into the computer.
  • Monitor : This is an output device which is used to show the result of the instructions.
There are variety of monitor available in the market such as, CRT Monitor, LCD Monitor, Touch Screen Monitor, TFT Monitor etc.
  • Switched Mode Power Supply (SMPS) : This is and electronic device which is used to manage the power supply of computer.
  • Hard Disk (HDD) : This is used to store the data in massive amount. There are so many type of HDD available in the market, i.e. SATA, PATA, External HDD, Internal HDD.
  • Printer : This is an out put device which is used to show the result on the paper. There are plenty of printer available in the market like inkjet, Laser printer, dot matrix printer etc.
Universal Serial Bus (USB) : This is used to connect the external device to the computer.
  • Ethernet Cable : This is used to connect computer with other computer.
  • CD/DVD ROM : This is used to store the data.
  • Speaker : This is an output device which is used to listen voice, songs, etc.
  • Mike : This is an Input device which is used to record the sound .
  • Laptop : This is complete computer which can be carried anywhere any time.
  • Netbook : This is called mini laptop which is generally lighter and smaller than laptop.
  • Random Access Memory (RAM) : This is called primary memory. This is also called main memory of the computer. Whatever data is written in this memory, is lost after switching off the system.
  • Read Only Memory (ROM) : This is called primary memory. Data is written in this memory by the vendor of the computer permanently.
  • Pen Drive : This is very popular device now a days for carrying data on move.
  • Blue Ray Disk : This is same as CD/DVD but only different is it can store multi time of data from CD/DVD and faster than CD/DVD.
  • Scanner : This is an input device which is used to scan the document for the soft copy.
  • LCD : It is known as Liqued Crystal Display. It is an output device as monitor.
  • Motherboard : It is a combination of electronic circuits.
  • Sound Card : This is also a combination of electronic circuits which helps to give out put in the form of sound.
  • Graphics Card : This is also a combination of electronic circuits which helps to give output the data into the monitor.

Computer Software

Software is a logical programme to handle/solve the complex problem.
  • System Software : This is special type of software which is responsible for handle the whole computer system.
  • Application Software : This is special type of software which is used to solve a particular problem.
  • Embeded Software : This type of software embeded with hardware to do a specific type of job.
  • Proprietary Software : In general, this type of software require to purchase to use that particular software for the some time or single user as per conditioned by the vendor of that particular software.
Open Source Software : This type of software may be freely available and can not be use in commercially. We can modify, and use it under the same license.

Computer Languages

  • Machine Level Language : This is low level programming language. Computer or any electronic device only understand this language. i.e. Binary number i.e 0 and 1.
  • Assembly Level Language : This is a low level programming language which is converted into executable machine code by a utility programmer referred to as an assembler.
  • High Level Language : High level language is a programming language which is easily understandable/readable by human.
  • Interpreter : This is a convertor which converts high level language programme to low level language programme line by line.
  • Compiler : This is also a convertor which converts whole high level language programme to low level language programme at a time.

Number System

  • Binary Number System : It has only base 2 i.e 0 and 1
  • Octal Number System  : Base of octal is 8 i.e. 0, 1, 2, 3, 4, 5, 6, 7
  • Decimal Number System : Base of Decimal is 10 i.e. 0 1 2 3 4 5 6 7 8 9
  • Hexadecimal Number System : Base of this number system is 16 i.e. 0 1 2 3 4 5 6 7 8 9 A B C D E F

Operating System

  • Windows : This is an Proprietary Operating system and vendor is Microsoft. i.e. Windows 2007, Windows vista, Windows 2008 etc.
  • Linux : This is an open source Operating System such as ubuntu, fedora, debian, mandriva, centOS etc.
Linux (Ubuntu ) Desktop Elements
File Management in Linux (Ubuntu)

Computer Security

  • Virus and worms : These are the computer programme which malfunction the computer system. Virus requires a carrier while worms does this by itself. Worm does not requires any carrier.
  • Spoofing : Through this, deceiving the computer users and making the fool.
  • Intrusion or Hacking : If a computer is used and controlled by unauthorised users then it is called hacking and who does this is called hacker. Main purpose of hacking to steal the private data or alter the actual data.
Denial of Services: The main aim of this attack is to bring down the targeted network and make it to deny the service for legitimate users.
Sniffing : Data can be seen and watched when it travels one computer to other computer. Generation of the Computer Charlse Babbase is known as father of computer he has invented first analytical computer in year 1822
  • First Generation (1940 – 1955) . Example : Electronic Numerical Integrator and Computer (ENIAC) , EDVAC
  • Second Generation (1956 – 1965) : IBM 1401
  • Third Generation (1966 – 1975) : IBM System/360
  • Fourth Generation (1976 – 1985) : Macintosh 128k
  • Fifth Generation (1986 -till date) : Super computer

The characteristics of computers that have made them so powerful and universally useful are speed, accuracy, diligence, versatility and storage capacity. Let us discuss them briefly.
  • Speed
Computers work at an incredible speed. A powerful computer is capable of performing about 3-4 million simple instructions per second.
  • Accuracy
In addition to being fast, computers are also accurate. Errors that may occur can almost always be attributed to human error (inaccurate data, poorly designed system or faulty instructions/programs written by the programmer)
  • Diligence
Unlike human beings, computers are highly consistent. They do not suffer from human traits of boredom and tiredness resulting in lack of concentration. Computers, therefore, are better than human beings in performing voluminous and repetitive jobs.
  • Versatility
Computers are versatile machines and are capable of performing any task as long as it can be broken down into a series of logical steps. The presence of computers can be seen in almost every sphere – Railway/Air reservation, Banks, Hotels, Weather forecasting and many more.
  • Storage Capacity
Today’s computers can store large volumes of data. A piece of information once recorded (or stored) in the computer, can never be forgotten and can be retrieved almost instantaneously.

                                                                   - http://oer.nios.ac.in/wiki/index.php/CHARACTERISTICS_OF_COMPUTERS

COMPUTER AND ITS COMPONENTS

          COMPUTER AND ITS COMPONENTS




A computer system consists of mainly four basic units; namely input unit, storage unit, central processing unit and output unit. Central Processing unit further includes Arithmetic logic unit and control unit, as shown in the figure:. A computer performs five major operations or functions irrespective of its size and make. These are
• it accepts data or instructions as input,
• it stores data and instruction
• it processes data as per the instructions,
• it controls all operations inside a computer, and
• it gives results in the form of output.
Desktop Computer System

Functional Units:

a. Input Unit: This unit is used for entering data and programs into the computer system by the user for processing.
Basic Computer Organisation

b. Storage Unit: The storage unit is used for storing data and instructions before and after processing.
c. Output Unit: The output unit is used for storing the result as output produced by the computer after processing.
d. Processing: The task of performing operations like arithmetic and logical operations is called processing. The Central Processing Unit (CPU) takes data and instructions from the storage unit and makes all sorts of calculations based on the instructions given and the type of data provided. It is then sent back to the storage unit. CPU includes Arithmetic logic unit (ALU) and control unit (CU)

Computer Chip
Arithmetic Logic Unit: All calculations and comparisons, based on the instructions provided, are carried out within the ALU. It performs arithmetic functions like addition, subtraction, multiplication, division and also logical operations like greater than, less than and equal to etc.
Control Unit: Controlling of all operations like input, processing and output are performed by control unit. It takes care of step by step processing of all operations in side the computer.

Memory

Computer’s memory can be classified into two types; primary memory and secondary memory
RAM
a. Primary Memory can be further classified as RAM and ROM.
• RAM or Random Access Memory is the unit in a computer system. It is the place in a computer where the operating system, application programs and the data in current use are kept temporarily so that they can be accessed by the computer’s processor. It is said to be ‘volatile’ since its contents are accessible only as long as the computer is on. The contents of RAM are no more available once the computer is turned off.

ROM or Read Only Memory is a special type of memory which can only be read and contents of which are not lost even when the computer is switched off. It typically contains manufacturer’s instructions. Among other things, ROM also stores an initial program called the ‘bootstrap loader’ whose function is to start the operation of computer system once the power is turned on.
b. Secondary Memory
RAM is volatile memory having a limited storage capacity. Secondary/auxiliary memory is storage other than the RAM. These include devices that are peripheral and are connected and controlled by the computer to enable permanent storage of programs and data.
  • CD ROM
Secondary storage devices are of two types; magnetic and optical. Magnetic devices include hard disks and optical storage devices are CDs, DVDs, Pen drive, Zip drive etc.
• Hard Disk
Hard disks are made up of rigid material and are usually a stack of metal disks sealed in a box. The hard disk and the hard disk drive exist together as a unit and is a permanent part of the computer where data and programs are saved. These disks have storage capacities ranging from 1GB to 80 GB and more. Hard disks are rewritable.
Compact Disk
Compact Disk (CD) is portable disk having data storage capacity between 650-700 MB. It can hold large amount of information such as music, full-motion videos, and text etc. CDs can be either read only or read write type.
CD Drive
• Digital Video Disk
Digital Video Disk (DVD) is similar to a CD but has larger storage capacity and enormous clarity. Depending upon the disk type it can store several Gigabytes of data. DVDs are primarily used to store music or movies and can be played back on your television or the computer too. These are not rewritable.

Hard Disk

Input / Output Devices:

These devices are used to enter information and instructions into a computer for storage or processing and to deliver the processed data to a user. Input/Output devices are required for users to communicate with the computer. In simple terms, input devices bring information INTO the computer and output devices bring information OUT of a computer system. These input/output devices are also known as peripherals since they surround the CPU and memory of a computer system.

Input Devices

An input device is any device that provides input to a computer. There are many input devices, but the two most common ones are a keyboard and mouse. Every key you press on the keyboard and every movement or click you make with the mouse sends a specific input signal to the computer.
Keyboard
• Keyboard: The keyboard is very much like a standard typewriter keyboard with a few additional keys. The basic QWERTY layout of characters is maintained to make it easy to use the system. The additional keys are included to perform certain special functions. These are known as function keys that vary in number from keyboard to keyboard.
• Mouse: A device that controls the movement of the cursor or pointer on a display screen. A mouse is a small object you can roll along a hard and flat surface. Its name is derived from its shape, which looks a bit like a mouse. As you move the mouse, the pointer on the display screen moves in the same direction.
Trackball: A trackball is an input device used to enter motion data into computers or other electronic devices. It serves the same purpose as a mouse, but is designed with a moveable ball on the top, which can be rolled in any direction.
Touchpad: A touch pad is a device for pointing (controlling input positioning) on a computer display screen. It is an alternative to the mouse. Originally incorporated in laptop computers, touch pads are also being made for use with desktop computers. A touch pad works by sensing the user’s finger movement and downward pressure. • Touch Screen: It allows the user to operate/make selections by simply touching the display screen. A display screen that is sensitive to the touch of a finger or stylus. Widely used on ATM machines, retail point-of-sale terminals, car navigation systems, medical monitors and industrial control panels.

Mouse
• Light Pen: Light pen is an input device that utilizes a light-sensitive detector to select objects on a display screen.
Light Pen
Magnetic ink character recognition (MICR): MICR can identify character printed with a special ink that contains particles of magnetic material. This device particularly finds applications in banking industry.
Optical mark recognition (OMR): Optical mark recognition, also called mark sense reader is a technology where an OMR device senses the presence or absence of a mark, such as pencil mark. OMR is widely used in tests such as aptitude test.
Bar code reader: Bar-code readers are photoelectric scanners that read the bar codes or vertical zebra strips marks, printed on product containers. These devices are generally used in super markets, bookshops etc.

Light Pen
Scanner

Scanner

Scanner is an input device that can read text or illustration printed on paper and translates the information into a form that the computer can use. A scanner works by digitizing an image. (Fig. 1.7)




Scanner

Output Devices:

Output device receives information from the CPU and presents it to the user in the desired from. The processed data, stored in the memory of the computer is sent to the output unit, which then converts it into a form that can be understood by the user. The output is usually produced in one of the two ways – on the display device, or on paper (hard copy).
Monitor: is often used synonymously with “computer screen” or “display.” Monitor is an output device that resembles the television screen (fig. 1.8). It may use a Cathode Ray Tube (CRT) to display information. The monitor is associated with a keyboard for manual input of characters and displays the information as it is keyed in. It also displays the program or application output. Like the television, monitors are also available in different sizes. • Printer: Printers are used to produce paper (commonly known as hard copy) output. Based on the technology used, they can be classified as Impact or Non-impact printers.
Impact printers use the typewriting printing mechanism wherein a hammer strikes the paper through a ribbon in order to produce output. Dot-matrix and Character printers fall under this category.
Monitor
Non-impact printers do not touch the paper while printing. They use chemical, heat or electrical signals to etch the symbols on paper. Inkjet, Deskjet, Laser, Thermal printers fall under this category of printers.

Plotter
• Plotter: Plotters are used to print graphical output on paper. It interprets computer commands and makes line drawings on paper using multi colored automated pens. It is capable of producing graphs, drawings, charts, maps etc. • Facsimile (FAX): Facsimile machine, a device that can send or receive pictures and text over a telephone line. Fax machines work by digitizing an image.
Plotter
Sound cards and Speaker(s): An expansion board that enables a computer to manipulate and output sounds. Sound cards are necessary for nearly all CD-ROMs and have become commonplace on modern personal computers. Sound cards enable the computer to output sound through speakers connected to the board, to record sound input from a microphone connected to the computer, and manipulate sound stored on a disk.
                              
                                                                   http://oer.nios.ac.in/wiki/index.php/COMPUTER_AND_ITS_COMPONENTS

Computer

Computer


-"Computer technology" and "Computer system" redirect here. For the company, see Computer Technology Limited. For other uses, see Computer (disambiguation) andComputer system (disambiguation).
Computer
Acer Aspire 8920 Gemstone.jpgColumbia Supercomputer - NASA Advanced Supercomputing Facility.jpgIntertec Superbrain.jpg
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DM IBM S360.jpgAcorn BBC Master Series Microcomputer.jpgDell PowerEdge Servers.jpg
computer is a general-purpose device that can be programmed to carry out a set of arithmetic or logical operations automatically. Since a sequence of operations can be readily changed, the computer can solve more than one kind of problem.
Conventionally, a 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 logic operations, and a sequencing and control unit can change the order of operations in response to stored informationPeripheral devices allow information to be retrieved from an external source, and the result of operations saved and retrieved.
Mechanical analog computers started appearing in the first century and were later used in the medieval era for astronomical calculations. In World War II, mechanical analog computers were used for specialized military applications such as calculating torpedo aiming. During this time the first electronic digital computers were developed. Originally they were the size of a large room, consuming as much power as several hundred modern personal computers (PCs).[1]
Modern computers based on integrated circuits are millions to billions of times more capable than the early machines, and occupy a fraction of the space.[2] Computers are small enough to fit into mobile devices, and mobile computers can be powered by small batteries. Personal computers in their various forms are icons of the Information Age and are generally considered as "computers". However, the embedded computers found in many devices from MP3 players to fighter aircraft and from electronic toys to industrial robots are the most numerous.

Etymology

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 read the truest computer of Times, and the best Arithmetician that euer breathed, and he reduceth thy dayes into a short number." It referred to a person who carried out calculations, or computations. The word continued with the same meaning until the middle of the 20th century. From the end of the 19th century the word began to take on its more familiar meaning, a machine that carries out computations.[3]

History

Pre-twentieth century

Devices have been used to aid computation for thousands of years, mostly using one-to-one 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.[4][5] The use of counting rods is one example.
Suanpan (the number represented on this abacus is 6,302,715,408)
The abacus was initially used for arithmetic tasks. The Roman abacus was 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 Greek-designedAntikythera mechanism, dating between 150 to 100 BC, is the world's oldest analog computer.
The Antikythera mechanism is believed to be the earliest mechanical analog "computer", according to Derek J. de Solla Price.[6] It was designed to calculate astronomical positions. It was discovered in 1901 in the Antikythera wreckoff the Greek island of Antikythera, between Kythera and Crete, and has been dated to circa 100 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 Abū Rayhān al-Bīrūnī in the early 11th century.[7] The astrolabe was invented in the Hellenistic world in either the 1st or 2nd centuries BC and is often attributed to Hipparchus. A combination of the planisphere and dioptra, the astrolabe was effectively an analog computer capable of working out several different kinds of problems in spherical astronomy. An astrolabe incorporating a mechanical calendar computer[8][9] and gear-wheels was invented by Abi Bakr of IsfahanPersia in 1235.[10] Abū Rayhān al-Bīrūnīinvented the first mechanical geared lunisolar calendar astrolabe,[11] an early fixed-wired knowledge processing machine[12] with a gear train and gear-wheels,[13] circa 1000 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 1620–1630, shortly after the publication of the concept of the logarithm. It is a hand-operated 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. Aviation is one of the few fields where slide rules are still in widespread use, particularly for solving time–distance problems in light aircraft. To save space and for ease of reading, these are typically circular devices rather than the classic linear slide rule shape. A popular example is the E6B.
In the 1770s Pierre Jaquet-Droz, a Swiss watchmaker, built a mechanical doll (automata) 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 Musée d'Art et d'Histoire of NeuchâtelSwitzerland, and still operates.[14]
The tide-predicting 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 wheel-and-disc 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 ball-and-disk integrators.[15] 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 general-purpose computing device

A portion of Babbage's Difference engine.
Charles Babbage, an English mechanical engineer and polymath, originated the concept of a programmable computer. Considered the "father of the computer",[16] he conceptualized and invented the first mechanical computer in the early 19th century. After working on his revolutionary difference engine, designed to aid in navigational calculations, in 1833 he realized that a much more general design, anAnalytical Engine, was possible. The input of programs and data was to be provided to the machine via punched cards, a method being used at the time to direct mechanical looms such as the Jacquard loom. 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 arithmetic logic unit,control flow in the form of conditional branching and loops, and integrated memory, making it the first design for a general-purpose computer that could be described in modern terms as Turing-complete.[17][18]
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. Babbage's 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 engine's computing unit (the mill) in 1888. He gave a successful demonstration of its use in computing tables in 1906.

Later Analog computers

Sir William Thomson's third tide-predicting machine design, 1879–81
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.[19]
The first modern analog computer was a tide-predicting machine, invented by Sir William Thomson in 1872. The differential analyser, a mechanical analog computer designed to solve differential equations by integration using wheel-and-disc mechanisms, was conceptualized in 1876 by James Thomson, the brother of the more famous Lord Kelvin.[15]
The art of mechanical analog computing reached its zenith with the differential analyzer, built by H. L. Hazen and Vannevar Bush at MITstarting 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 remain in use in some specialized applications such as education (control systems) and aircraft (slide rule).

Digital computer development

The principle of the modern computer was first described by mathematician and pioneering computer scientist Alan Turing, who set out the idea in his seminal 1936 paper,[20] On Computable Numbers. Turing reformulated Kurt Gödel's 1931 results on the limits of proof and computation, replacing Gödel's universal arithmetic-based formal language with the formal and simple hypothetical devices that became known as Turing machines. He proved that some such machine would be capable of performing any conceivable mathematical computation if it were representable as an algorithm. He went on to prove that there was no solution to the Entscheidungsproblem by first showing that the halting problem for Turing machines is undecidable: in general, it is not possible to decide algorithmically whether a given Turing machine will ever halt.
He also introduced the notion of a 'Universal Machine' (now known as a Universal Turing machine), with the idea that such a machine could perform the tasks of any other machine, or in other words, it is provably capable of computing anything that is computable by executing a program stored on tape, allowing the machine to be programmable.Von Neumann acknowledged that the central concept of the modern computer was due to this paper.[21] 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 Turing-complete, which is to say, they have algorithm execution capability equivalent to a universal Turing machine.

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 Zuse's 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 all-electric 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.[22]
In 1941, Zuse followed his earlier machine up with the Z3, the world's first working electromechanical programmable, fully automatic digital computer.[23][24] The Z3 was built with 2000 relays, implementing a 22 bit word length that operated at a clock frequency of about 5–10 Hz.[25]Program code was supplied on punched film 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 floating point numbers. Replacement of the hard-to-implement decimal system (used in Charles Babbage's earlier design) by the simpler binary system meant that Zuse's machines were easier to build and potentially more reliable, given the technologies available at that time.[26] The Z3 was probably a complete Turing machine.

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 engineerTommy 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 5 years later, converting a portion of the telephone exchange network into an electronic data processing system, using thousands of vacuum tubes.[19] In the US, John Vincent Atanasoff and Clifford E. Berry of Iowa State University developed and tested the Atanasoff–Berry Computer (ABC) in 1942,[27] the first "automatic electronic digital computer".[28] This design was also all-electronic and used about 300 vacuum tubes, with capacitors fixed in a mechanically rotating drum for memory.[29]
Colossus was the first electronicdigital programmable computing device, and 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 electro-mechanical bombes. To crack the more sophisticated German Lorenz SZ 40/42 machine, used for high-level Army communications, Max Newman and his colleagues commissioned Flowers to build the Colossus.[29] He spent eleven months from early February 1943 designing and building the first Colossus.[30] After a functional test in December 1943, Colossus was shipped to Bletchley Park, where it was delivered on 18 January 1944[31] and attacked its first message on 5 February.[29]
Colossus was the world's first electronic digital programmable computer.[19] 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 boolean logical operations on its data, but it was not Turing-complete. Nine Mk II Colossi were built (The Mk I was converted to a Mk II making ten machines in total). Colossus Mark I contained 1500 thermionic valves (tubes), but Mark II with 2400 valves, was both 5 times faster and simpler to operate than Mark 1, greatly speeding the decoding process.[32][33]
ENIAC was the first Turing-complete device, and performed ballistics trajectory calculations for the United States Army.
The US-built ENIAC[34] (Electronic Numerical Integrator and Computer) was the first electronic programmable computer built in the US. Although the ENIAC was similar to the Colossus it was much faster and more flexible. It was unambiguously a Turing-complete device and could compute any problem that would fit into its memory. Like the Colossus, a "program" on the ENIAC was defined by the states of its patch cables and switches, a far cry from the stored program 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.
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, 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.[35]

Stored programs

Three tall racks containing electronic circuit boards
A section of the Manchester Small-Scale Experimental Machine, the first stored-program computer.
Early computing machines had fixed programs. Changing its function required the re-wiring and re-structuring of the machine.[29] With the proposal of the stored-program computer this changed. A stored-program computer includes by design an instruction set and can store in memory a set of instructions (a program) that details the computation. The theoretical basis for the stored-program computer was laid by Alan Turing in his 1936 paper. In 1945 Turing joined the National Physical Laboratory 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 University of Pennsylvania, also circulated his First Draft of a Report on the EDVAC in 1945.[19]
Ferranti Mark 1, c. 1951.
The Manchester Small-Scale Experimental Machine, nicknamed Baby, was the world's first stored-program computer. It was built at the Victoria University of Manchester by Frederic C. WilliamsTom Kilburn and Geoff Tootill, and ran its first program on 21 June 1948.[36] It was designed as a testbedfor the Williams tube the first random-access digital storage device.[37] 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.[38] As soon as the SSEM had demonstrated the feasibility of its design, a project was initiated at the university to develop it into a more usable computer, the Manchester Mark 1.
The Mark 1 in turn quickly became the prototype for the Ferranti Mark 1, the world's first commercially available general-purpose computer.[39]Built by Ferranti, it was delivered to the University of Manchester in February 1951. At least seven of these later machines were delivered between 1953 and 1957, one of them to Shell labs in Amsterdam.[40] In October 1947, the directors of British catering company J. Lyons & Company decided to take an active role in promoting the commercial development of computers. The LEO I computer became operational in April 1951 [41] and ran the world's first regular routine office computer job.

Transistors

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 developedtransistors instead of valves.[42] Their first transistorised computer and the first in the world, was operational by 1953, 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 drum memory, so it was not the first completely transistorized computer. That distinction goes to the Harwell CADET of 1955,[43] built by the electronics division of the Atomic Energy Research Establishment at Harwell.[44][45]

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 DefenceGeoffrey W.A. Dummer. Dummer presented the first public description of an integrated circuit at the Symposium on Progress in Quality Electronic Components in Washington, D.C. on 7 May 1952.[46]
The first practical ICs were invented by Jack Kilby at Texas Instruments and Robert Noyce at Fairchild Semiconductor.[47] Kilby recorded his initial ideas concerning the integrated circuit in July 1958, successfully demonstrating the first working integrated example on 12 September 1958.[48] 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".[49][50] Noyce also came up with his own idea of an integrated circuit half a year later than Kilby.[51] His chip solved many practical problems that Kilby's had not. Produced at Fairchild Semiconductor, it was made of silicon, whereas Kilby's 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 single-chip microprocessor was the Intel 4004,[52] designed and realized by Ted HoffFederico Faggin, and Stanley Mazor at Intel.[53]

Mobile computers become dominant

With the continued miniaturization of computing resources, and advancements in portable battery life, portable computers grew in popularity in the 2000s.[54] The same developments that spurred the growth of laptop computers and other portable computers allowed manufacturers to integrate computing resources into cellular phones. These so-called smartphones and tablets run on a variety of operating systems and have become the dominant computing device on the market, with manufacturers reporting having shipped an estimated 237 million devices in 2Q 2013.
                                                                                                                           - https://en.wikipedia.org/wiki/Computer