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Definition of a Computer

The most obvious question you should ask is, What is a computer? A computer is an electronic device that operates under the control of a set of instructions that is stored in its memory unit. A computer accepts data from an input device and processes it into useful information which it displays on its output device. Actually, a computer is a collection of hardware and software components that help you accomplish many different tasks. Hardware consists of the computer itself, and any equipment connected to it. Software is the set of instructions that the computer follows in performing a task. We will explore hardware and software more in depth in the next module.

history

A hundred years later, in the early 1940s, electromagnetic relays could be used instead of gearwheels. But no-one had advanced on Babbage's principle. Builders of large calculators might put the program on a roll of punched paper rather than cards, but the idea was the same: you built machinery to do arithmetic, and then you arranged for instructions coded in some other form, stored somewhere else, to make the machinery work.

To see how different this is from a computer, think of what happens when you want a new piece of software. You can download it from a remote source, and it is transmitted by the same means as email or any other form of data. You may apply an UnStuffIt or GZip program to it when it arrives, and this means operating on the program you have ordered. For filing, encoding, transmitting, copying, a program is no different from any other kind of data — it is just a sequence of electronic on-or-off states which lives on hard disk or RAM along with everything else.

The people who built big electromechanical calculators in the 1930s and 1940s didn't think of anything like this. I would call their machines near-computers, or pre-computers: they lacked the essential idea.

So who invented the computer?

There are many different views on which aspects of the modern computer are the most central or critical.

• Some people think that it's the idea of using electronics for calculating — in which case another American pioneer, Atanasoff, should be credited.


• Other people say it's getting a computer actually built and working. In that case it's either the tiny prototype at Manchester, (See this Scrapbook Page) or the EDSAC at Cambridge, England (1949), that deserves greatest attention.

But I would say that in 1945 Alan Turing alone grasped everything that was to change computing completely after that date: above all he understood the universality inherent in the stored-program computer. He knew there could be just one machine for all tasks. He did not do so as an isolated dreamer, but as someone who knew about the practicability of large-scale electronics, with hands-on experience. From experience in codebreaking and mathematics he was also vividly aware of the scope of programs that could be run.

The idea of the universal machine was foreign to the world of 1945. Even ten years later, in 1956, the big chief of the electromagnetic relay calculator at Harvard, Howard Aiken, could write:

If it should turn out that the basic logics of a machine designed for the numerical solution of differential equations coincide with the logics of a machine intended to make bills for a department store, I would regard this as the most amazing coincidence that I have ever encountered.

But that is exactly how it has turned out. It is amazing, although we now have come to take it for granted. But it follows from the deep principle that Alan Turing saw in 1936: the Universal Turing Machine.

 

GENERATION'S OF COMPUTER

   1. First generation: Vacuum tubes (left). Mid 1940s. IBM pioneered the arrangment of vacuum tubes in pluggable modules such as the one shown here on the left. The IBM 650 was a first-generation computer.

Apart from the computers discussed above, some other notable devices of the first generation were EDSAC by Maurice Wilkes (1949), BINAC by Eckert's and Mauchly's Electronic Control Company (1949). Whirlwind I by J. Forrester (1949), SEAC by Samuel Alexander and Ralph Slutz (1950), SWAC by Harry Huskey (1950), UNIVAC by Eckert-Mauchly Corporation (1951), IAS computer by Institute of Advanced Study (1952) and IBM 701, 1952.

The first generation computers were run by several types of memories and the gradual advancement in the technology applied for development of memories deserves mention. Mercury filled tubes called "Delay Lines" were used for high speed internal memory in computers like EDSAC, BINAC, SEAC, DEUCE and pilot model of ACE. In Manchester baby it was the electronic memory where a two-dimensional rectangular array of binary digits was stored on the face of a cathode ray tube.

This technique was also employed in SWAC, IAS computers and IBM 701. In drum memory, data was stored magnetically on the surface of a metal cylinder. The final discovery in the history of first generation computer was the development of magnetic core memory by Jay Forrester. The ferrite core memory, as it was called, was tested in a computer in 1953 and the device was put to use in 1954 for the first simulations of the neural network.

   2. Second generation: Transistors (right). 1956. The era of miniaturization begins. Transistors are much smaller than vacuum tubes, draw less power, and generate less heat. Discrete transistors are soldered to circuit boards like the one shown, with intereconnections accomplished by stencil-screened conductive patterns on the reverse side. The IBM 7090 was a second-generation computer.

The transition from first generation to second generation of computers was not abrupt. There was all round development in technology, designs and programming languages. Diode and transistor technology formed the basis of the electronic switches and the switching time came down to around 0.3 microseconds.

Computers like TRADIC and TX-0 built in 1954 used this technology. During this span, the superior magnetic core memory was in use. Some of the significant innovations of this era are floating point units for the real number calculations and index registers for controlling loops. This saved the ordeal of writing self-modifying codes and made the access to successive elements easy.

In the field of programming languages, there were superior introductions like FORTRAN (1956), ALGOL (1958) and COBOL (1959). The second generation also witnessed the development of two supercomputers - i.e. the most powerful devices amongst the peers. These two were the Liverpool Atomic Research Computer (LARC) and IBM7030. These machines overlapped memory operations with processor operations and had primitive type of parallel processing. Some of the important commercial machines of this era were IBM 704, 709 and 7094. The later introduced I/O processing.


   3. Third generation: Integrated circuits (foreground), silicon chips contain multiple transistors. 1964. A pioneering example is the ACPX module used in the IBM 360/91, which, by stacking layers of silicon over a ceramic substrate, accommodated over 20 transistors per chip; the chips could be packed together onto a circuit board to achieve unheard-of logic densities. The IBM 360/91 was a hybrid second- and third-generation computer.

In this era, there were several innovations in various fields of computer technology. These include Integrated Circuits (ICs), Semiconductor Memories, Microprogramming, various patterns of parallel processing and introduction of Operating Systems and time-sharing. In the Integrated Circuit, division there was gradual progress. Firstly, there were small-scale integration (SSI) circuits (having 10 devices per chip), which evolved to medium scale integrated (MSI) circuits (having 100 devices per chip). There were also developments of multi-layered printed circuits.

Parallelism became the trend of the time and there were abundant use of multiple functional units, overlapping CPU and I/O operations and internal parallelism in both the instruction and the data streams. Functional parallelism was first embodied in CDC6600, which contained 10 simultaneously operating functional units and 32 independent memory banks. This device of Seymour Cray had a computation of 1 million flopping point per second (1 M Flops). After 5 years CDC7600, the first vector processor was developed by Cray and it boasted of a speed of 10 M Flops. IBM360/91 was a contemporary device and was twice as first as CDC6600, whereas IBM360-195 was comparable to CDC7600. In case of language, this era witnessed the development of CPL i.e. combined programming language (1963). CPL had many difficult features and so in order to simplify it Martin Richards developed BCPL - Basic Computer Programming Language (1967). In 1970 Ken Thompson developed yet another simplification of CPL and called it B.

 4.Fourth Generation of Computers (1972-1984)

In this generation, there were developments of large-scale integration or LSI (1000 devices per chip) and very large-scale integration or VLSI (10000 devices per chip). These developments enabled the entire processor to fit into a single chip and in fact, for simple systems, the entire computer with processor; main memory and I/O controllers could fit on a single chip.

Core memories now were replaced by semiconductor memories and high-speed vectors dominated the scenario. Names of few such vectors were Cray1, Cray X-MP and Cyber205. A variety of parallel architectures developed too, but they were mostly in the experimental stage.

As far as programming languages are concerned, there were development of high-level languages like FP or functional programming and PROLOG (programming in logic). Declarative programming style was the basis of these languages where a programmer could leave many details to the compiler or runtime system. Alternatively languages like PASCAL, C used imperative style. Two other conspicuous developments of this era were the C programming language and UNIX operating system. Ritchie, the writer of C and Thompson together used C to write a particular type of UNIX for DEC PDP 11. This C based UNIX was then widely used in many computers.

Another event that is mention worthy was the publication of the report by Peter D. Lax in 1982, which was sponsored by the US department and National Scientific Foundation. The Lax report, as it was called, emphasized on the need of initiatives and coordinated national attention in the arena of high performing computing in the US. The immediate response to the Lax report was the establishment of NSF Supercomputing Centers. Other centers that came up later were San Diego Supercomputing Center, National Center for Supercomputing Applications, Pittsburgh Supercomputing Center, John von Neumann Center and Cornell Theory Center. These institutes had really been instrumental in providing computing time on super computers to the students, training them and also helping in the development of software packages.

   5.Fifth generation of computers (1984-1990)

In this period, computer technology achieved more superiority and parallel processing, which was until limited to vector processing and pipelining, where hundreds of processors could all work on various parts of a single program. There were introduction of systems like the Sequent Balance 8000, which connected up to twenty processors to one shared memory module.

This machine was as competent as the DEC VAX-780 in the context that it had a general purpose UNIX system and each processor worked on a different user's job. On the other hand, INTEL IPSC-I or Hypercube, as it was called, connected each processor to its own memory and used a network interface to connect the processors. With the concept of distributed network coming in, memory posed no further problem and the largest IPSC-I was built with 128 processors. Towards the end of the fifth generation, another parallel processing was introduced in the devices, which were called Data parallel or SIMD. In this system, all the processors operate under the instruction of a single control unit.

In this generation semiconductor memories became the standard were pursued vigorously. Other developments were the increasing use of single user workstations and widespread use of computer networks. Both wide area network (WAN) and local area network (LAN) developed at an incredible pace and led to a distributed computing environment. RISC technology i.e. a particular technique for the internal organization of CPU and the plunging cost of RAM ushered in huge gains in computational power of comparatively cheaper servers and workstations. This generation also witnessed a sharp increase in both quantitative and qualitative aspects of scientific visualization.

  6.Sixth generation of computers (1990 -till date)

Of all those changes that have taken place in the field of computer technology, some changes are abrupt whereas others are defined. In the current period, this transition from one period to another is clear only in retrospect because most of them are gradual advancements of an already established system. This present generation of computer technology is highly related with parallel computing and several growth areas has been noticed in this area, in both hardware part and in the better understanding of how to develop algorithms to make full use of massive parallel architectures.

Though vector system is equally in use, it is often speculated that the future would be dominated by parallel systems. However, there are several devices where there are combinations of parallel-vector architectures. Fujitsu Corporation is planning to build a system with more than 200 vector processors. Another goal of this sixth generation is to attain Teraflops i.e. ten arithmetic operations per second and that can be done by building up a system with more than thousand processors. Currently, the processors are constructed with a combination of RISC, pipelining and parallel processing.

Networking technology is spreading rapidly and one of the most conspicuous growths of the sixth generation computer technology is the huge growth of WAN. For regional network, T1 is the standard and the national "backbone" uses T3 to interconnect the regional networks. Finally, the rapid advancement and high level of awareness regarding computer technology is greatly indebted to the two legislations. Just like the Lax report of 1982, the High Performance Computing Act of 1991, Information Infrastructure, and technology Act of 1992 have strengthened and ensured the scope of high performance computing. The former has ensured the establishment of high performance computing and communications programming (HPCCP) and the later has reinforced the necessity of making leading edge technologies available to academicians right from kindergarten up to graduation level.

INPUT AND OUTPUT DEVICE



INPUT DEVICE

Keyboards

A keyboard is a human interface device which is represented as a layout of buttons. Each button, or key, can be used to either input a linguistic character to a computer, or to call upon a particular function of the computer. Traditional keyboards use spring-based buttons, though newer variations employ virtual keys, or even projected keyboards.

TWO TYPES ONE IS MEMBRANE & MECHANICAL KEYBOAD

Pointing devices

A pointing device is any human interface device that allows a user to input spatial data to a computer. In the case of mice and touch screens, this is usually achieved by detecting movement across a physical surface. Analog devices, such as 3D mice, joysticks, or pointing sticks, function by reporting their angle of deflection. Movements of the pointing device are echoed on the screen by movements of the cursor, creating a simple, intuitive way to navigate a computer's GUI.

Touchscreen
A touchscreen is an input device that allows users to operate a PC by simply touching the display screen. Touch input is suitable for a wide variety of computing applications. A touchscreen can be used with most PC systems as easily as other input devices such as track balls or touch pads. Browse the links below to learn more about touch input technology and how it can work for you.