WHAT IS ORIGIN OF COMPUTERS
Origin of computer could be rigorous efforts of men to count large numbers. This process of counting of large numbers generated various systems of numeration like Babylonian system of numeration, Greek system of numeration, Roman system of numeration and Indian system of numeration. Out of these the Indian system of numeration has been accepted universally. It is the basis of modern decimal system of numeration 0-9.
Abacus
Nearly 5,000 years ago, the "abacus" was developed in China in 3000 B.C. The word abacus means calculating board. The "abacus" may be considered the first computer and it has been used since ancient times by a number of civilizations for basic arithmetical calculations. A modern form of abacus is given in Figure.
Figure: Abacus
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The major innovations in this generation were the development of microelectronics and the different areas in computer technology such as multiprocessing, multiprogramming, time-sharing, operating speed, and virtual storage. During this period, high speed vector processors changed the scenario of high performance computing. Mostly microcomputers and workstations were introduced for time shared mainframe computers. Thus the computer which was occupying a very large room in earlier days can now be placed on a table. The personal computer is a Fourth Generation Computer. It is the period when evolution of computer networks also took place.
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The abacus is also called a counting frame, which is a calculating tool for performing arithmetic operations. The Chinese abacus has a frame holding vertical wires, with seven beads on each wire. A horizontal divider separates the top two beads from the bottom five, sometimes referred to as the heaven and the earth beads. The arithmetic calculations are performed by manipulating the beads by using the principle of positional weight of beads on a rack. Abacus is used even today to teach small children how to count. A skilled abacus operation can be as fast as a hand held calculator.
Napier's Bones
John Napier was a mathematician who became famous for his invention of logarithms. The used of "logs" enabled him to reduce any multiplication problem. John Napier built a mechanical device for the purpose of multiplication in 1617 A.D. The device was known as Napier‟s bones. His "bones" are set of eleven rods side by side products and quotients of large numbers can be obtained. The sticks were called "bones" because they were made of bone of ivory.
Slide Rule
English mathematician E. Gunter developed the slide rule. This machine could perform operations like addition, subtraction, multiplication, and division. Although the slide rule appeared in various forms during the seventeenth century, it consists of two movable rulers placed side by side. Each ruler is marked off in such a way that the actual distances from the beginning of the ruler are proportional to the logarithms of the numbers printed on the ruler. By sliding the rulers, one can quickly multiply and divide.
Pascal's Calculator
Blaise Pascal was a French mathematician and one of the first modern scientists to developed and build calculator. He developed a machine at the age of 19 that was capable of adding and subtracting numbers. The machine was operated by dialing a series of wheels, gears and cylinders.
Leibniz's Multiplication and Dividing Machine
Like Pascal, Gottfried Leibniz was a seventeenth century scientist who recognized the value of building machines and built around 1673 a mechanical device that could do mathematical calculations and save labor too.
Difference Engine
The first step towards the creation of computers was made by an English mathematics professor, Charles Babbage. Early on, he realized that all mathematical calculations can be broken up into simple operations which are then constantly repeated, and that these operations could be carried out by an automatic machine. In the 1820s Charles Babbage started working on a „Difference Engine‟, but after ten years he abandoned it for the „Analytical Engine‟ – the real predecessor of the Computer.
Babbage outlined the basic elements of a modern general purpose computer which was based on the method of finite differences. It uses only arithmetical addition and removes the need for multiplication and division which are more difficult to implement mechanically. Charles Babbage is called the father of the computer.
The Analytical Engine
The Analytical Engine marks the progression from the arithmetic calculation to general-purpose computation. It was also developed by Charles Babbage. This machine was based on the principle that, for certain formulas, the difference between certain values is constant. The Analytical Engine has many essential features found in the modern digital computer.
The Engine had a 'Store' (memory) where numbers and intermediate results could be held, and a separate 'Mill' (processor) where the arithmetic processing was performed. It had an internal stock of the four arithmetical functions and could perform direct multiplication and division. It was also capable of functions like: conditional branching, looping (iteration), microprogramming, parallel processing, latching, and polling etc. The logical structure of the Analytical Engine was essentially the same as that which has dominated computer design in the electronic era.
Mechanical and Electrical Calculator
In the beginning of 19th century, the mechanical calculator was developed to perform all sorts of mathematical calculations. Up to the 1960s, it was widely used. Later the rotating part of mechanical calculator was replaced by electric motor. So it was called the electrical calculator.
Modern Electronic Calculator
The electronic calculator used in 1960s was run with electron tubes, which was quite bulky. Later it was replaced with transistors and as a result the size of calculators became fairly small. The modern electronic calculator can compute all kinds of mathematical computations and mathematical functions. It can also be used to store some data permanently. Some calculators have in-built programs to perform some complicated calculations. Modern electronic calculators contain a keyboard with buttons for digits and arithmetical operations. These calculators can perform sophisticated arithmetic and financial computations such as converting from polar to rectangular coordinates, taking square roots, computing logarithms and trigonometric relationships.
Figure: Electronic Calculator
WHAT IS COMPUTER GENERATIONS
The evolution of computer started from 16th century and resulted in today‟s modern machines. The present day computer, however, has also undergone rapid change over the years. This period, during which the evolution of computer took place, can be divided into five distinct phases known as Generations of Computers. Each new generation of computers is not only superior from their predecessor in processing and capabilities but also differs in looks and sizes. Each phase is distinguished from others on the basis of the type of switching circuits used. These Generations are:
· First Generation Computers (1940-1956)
· Second Generation Computers (1956-1963)
· Third Generation Computers (1964-1971)
· Fourth Generation Computers (1971-Present)
· Fifth Generation Computers (Present and Beyond)
First Generation Computers: Vacuum Tubes (1940-1956)
First generation computers are characterized by the use of vacuum tube. A vacuum tube was a fragile glass device, which used filaments as a source of electronics. It could control and amplify electronic signals. These vacuum tubes were used for calculation as well as storage and control. The first general purpose programmable electronic computer was the Electronic Numerical Integrator and Computer (ENIAC), built by J. Presper Eckert and John V. Mauchly at the University of Pennsylvania. The ENIAC was 30-50 feet long, weighed 30 tons, contained 18,000 vacuum tubes, 70,000 registers, 10,000 capacitors and required 150,000 watts of electricity. First generation computers were too bulky in size which required large room for installation and they used to emit large amount of heat, so air-condition was must for the proper working of computers. Programs written in high level programming languages retranslated into assembly language or machine language by a compiler. Assembly language program retranslated into machine language by a program called an assembler (assembly language compiler).
Before ENIAC was finished, Von Neumann designed the Electronic Discrete Variable Automatic Computer (EDVAC) with a memory to hold both a stored program as well as data. This enabled much faster operation since the computer had rapid access to both data and instructions. The other advantages of storing instruction were that computer could do logical decision internally. Eckert and Mauchly later developed what was arguably the first commercially successful computer, the Universal Automatic Computer (UNIVAC), in 1952.
Examples: ENIAC, EDVAC, UNIVAC-1
Second Generation Computers: Transistors (1956-1963)
Solid-State components (transistors and diodes) and magnetic core storage formed the basis for the second generation of computers. Transistor is a device composed of semiconductor material that amplifies a signal or opens or closes a circuit. Invented in Bell Labs, transistors have become the key ingredient of all digital circuits, including computers. Transistor replaced the bulky electric tubes in the first generation computer. Transistors perform the same functions as a vacuum tube, except that electrons move through solid materials instead of through a vacuum. Transistors were made of a semi-conducting material and controlled the flow of electricity through the circuit. They also allowed computers to become smaller and more powerful and faster at the same time. They are also less expensive, required less electricity and emitted less heat than vacuum tubes. Manufacturing cost was also very low.
It is in the second generation that the concept of Central Processing Unit (CPU), memory, programming language and input and output units were developed. Second-generation computers moved from cryptic binary machine language to symbolic, or assembly, languages, which allowed programmers to specify instructions in words. These were also the first computers that stored their instructions in their memory, which moved from a magnetic drum to magnetic core technology. During the second generation many high level programming languages were introduced, including FORTRAN (1956), ALGOL (1958) and COBOL (1959).
Examples: PDP-8, IBM1400 series, IBM 1620, IBM 7090, CDC 3600
Third Generation Computers: Integrated Circuits (1964-1971)
The third generation computers were introduced in 1964. Transistors were miniaturized and placed on silicon chips, called semiconductors, which drastically increased the speed and efficiency of computers. They used Integrated Circuits (ICs). The development of ICs proved to be a milestone in the field of computer and electronics. These ICs are popularly known as chips.
Silicon is the basic material used to make computer chips, transistors, silicon diodes and other electronic circuits and switching devices because its atomic structure makes the element an ideal semiconductor. Silicon is commonly doped, or mixed, with other elements, such as boron, phosphorous and arsenic, to alter its conductive properties. A typical chip is less than ¼-square inches and can contain millions of electronic components (transistors). Computers consist of many chips placed on electronic boards called printed circuit boards. There are different types of chips. For example, CPU chips (also called microprocessors) contain an entire processing unit, whereas memory chips contain blank memory.
A single IC, has many transistors, registers and capacitors built on a single thin slice of silicon. Development in ICs ranges from small scale integration (SSI) to medium scale integration (MSI). Multilayered printed circuits were developed and core memory was replaced by faster, solid state memories. The IC technology was also known as
"microelectronics" technology, since large number of circuit could be integrated on a single chip.
Computers of this generation were small in size, low cost, large memory and processing speed is very high. Higher level language such as BASIC (Beginners All purpose Symbolic Instruction Code) was developed during this period. Integrated solid-state circuitry, improved secondary storage devices, and new input/output devices were the most important advantages in this generation. The new circuitry increased the speed of the computer. Arithmetic and logical operations were now being performed in microseconds or even nanoseconds. The development of mini computers also took place during this generation.
Examples: NCR 395, B6500, IBM 360,370
Fourth Generation Computers: Microprocessors (1971-Present)
Fourth generation computers started around 1971 by using large scale of integration (LSI) in the construction of computing elements. LSI circuits built on a single silicon chip called microprocessors. A microprocessor contains all the circuits required to perform arithmetic, logic and control functions on a single chip. Because of microprocessors, the fourth generation includes more data processing capacity than equivalent-sized third generation computers. Due to the development of microprocessor it is possible to place computer‟s central processing unit (CPU) on single chip. These computers are called microcomputers. Later very large scale Integrated (VLSI) circuits replaced LSI circuits. What in the first generation filled an entire room could now fit in the palm of the hand. The Intel 4004chip, developed in 1971, located all the components of the computer - from the central processing unit and memory to input/output controls - on a single chip.
Examples: Apple II, Alter 8800
1.3.5 Fifth Generation Computers (Present and Beyond)
Fifth generation computers, based on artificial intelligence, are still in development, though there are some applications, such as voice recognition, that are being used today. Artificial Intelligence is the branch of computer science concerned with making computers behave like humans and allow the computer to take its own decision. Currently, no computers exhibit full artificial intelligence (that is, are able to simulate human behavior). The greatest advances have occurred in the field of games playing. The best computer chess programs are now capable of beating humans. Today, the hottest area of artificial intelligence is neural networks, which are proving successful in an umber of disciplines such as voice recognition and natural-language processing. There are several programming languages that are known as AI languages because they are used almost exclusively for AI applications. The two most common are LISP and Prolog. The speed is extremely high in fifth generation computer. In the development of Fifth generation computers, parallel processing attended the main focus of developers. Until this time, parallelism was limited to pipelining and vector processing. This generation introduced machines with hundreds of processors that could all be working on different parts of a single program. Developments of more powerful computers are still in progress. It has been predicted that such a computer will be able to communicate in natural spoken language with its user, store vast knowledge databases, search rapidly through these databases, making intelligent inferences, drawing logical conclusions, image processing and see objects in the way that humans do.
Table shows the comparative features of five generations of computers:
Criteria
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First
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Second
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Third
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Fourth
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Fifth
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Generation
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Generation
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Generation
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Generation
|
Generation
| |
Computer
|
Computer
|
Computer
|
Computer
|
Computer
| |
Technology
|
Vacuum Tube
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Transistor
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Integrated
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Microprocessor
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Artificial
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Circuit
|
Intelligent
| ||||
Speed
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Slowest
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Slow
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Medium
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Faster
|
Fastest
|
Size
|
Largest
|
Large
|
Medium
|
Smaller
|
Smallest
|
Reliability
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Unreliable
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Less Reliable
|
More Reliable
|
More Reliable
|
More Reliable
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Operating
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None
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None
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Yes
|
Yes
|
Yes
|
System
| |||||
Language
|
Machine
|
Assembly
|
High Level
|
High Level
|
High Level
|
Period
|
1940-1956
|
1956-1963
|
1964-1971
|
1971-Present
|
Present and
|
Beyond
| |||||
WHAT IS COMPUTER SYSTEM
Each computer consists of a series of devices that together operate as an integrated unit or computer system. The processor is made up of the memory, arithmetic, logic and control units. A large computer system will normally have one or more auxiliary units, where input and output data are stored. A brief description of computer system is given here. More detailed study about this will be covered in unit 2 in this block.
How Computers Work ?
Input: This is the process of entering data and programs in to the computer system. Since computer is an electronic machine like any other machine which takes as inputs raw data and performs some processing giving out processed data, the input unit takes data from user to the computer in an organized manner for processing. Information and programs are entered into the computer through input devices such as the keyboard, disks, or through other computers via network connections or modems connected to the internet.
Storage: The process of saving data and instructions permanently is known as storage. Data has to be fed into the system before the actual processing starts. It is because the processing speed of Central Processing Unit (CPU) is so fast that the data has to be provided to CPU with the same speed. Therefore the data is first stored in the storage unit for faster access and processing. This storage unit or the primary storage of the computer system is designed to do the above functionality. It provides space for storing data and instructions. The storage unit performs the following major functions:
(a) All data and instructions are stored here before and after processing.
(b) Intermediate results of processing are also stored here.
Figure: Basic Computer Operations
Processing: The task of performing operations like arithmetic and logical operations is called processing. The CPU or central processing unit 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. The coprocessor or the arithmetic-logic unit does arithmetic and logical operations. The RAM temporarily stores information.
Output: This is the process of producing results from the data for getting useful information. Output devices display information on the screen (monitor) or the printer and sends information to other computers. They also display messages about what errors may have occurred and brings up message or dialog box asking for more information to be input. Again the output is also stored inside the computer for further processing.
Figure: Computer
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Operational Unit
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In order to carry out the operations, the computer allocates the task among its various
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operational units. These are 1) arithmetic logical unit, 2) control unit, and 3) central
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processing unit.
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Arithmetic Logical Unit (ALU)
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The Arithmetic Logical Unit is an important component of the CPU, which carry the
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actual execution of the instructions. After entering the data through the input device it is stored in the primary storage unit. Then processing of the data and instruction are performed by Arithmetic Logical Unit. The major operations performed by the ALU are addition, subtraction, multiplication, division, logic and comparison. Data is transferred to ALU from storage unit when required. After processing, the output is returned to the storage unit for further processing or getting stored.
Control Unit (CU)
The next component of computer is the Control Unit, which acts like the supervisor seeing that things are done in proper fashion. The control unit determines the sequence in which computer programs and instructions are executed. Things like processing of programs stored in the main memory, interpretation of the instructions and issuing of signals for other units of the computer to execute them. It also acts as a switch board operator when several users access the computer simultaneously. Thereby it coordinates the activities of computer‟s peripheral equipment as they perform the input and output.
Therefore, it is the manager of all operations mentioned in the previous section.
Central Processing Unit (CPU)
The ALU and the CU of a computer system are jointly known as the central processing unit. The term CPU relates to a specific chip or the processor. CPU may be considered as the brain of any computer system. It is just like brain that takes all major decisions, makes all sorts of calculations and directs different parts of the computer functions by activating and controlling the operations. The fundamental operation of most CPU is to execute a series of instructions called as a program. The different chip manufacturers use different measuring standards to measure the processor‟s speed. It depends on the circuit board that the chip is housed in, or the motherboard. The motherboard contains the circuitry and connections that allow the various components to communicate with each other.
System Unit
A computer system unit contains many parts :
Ports and Connectors : A port is a connector located on the motherboard or on a separate adapter. Ports and Connectors allow the computer to communicate with different devices and peripherals attached with it.
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Power Supply : Power supply changes normal household electricity into electricity that a computer can use. A power supply or power supply unit (PSU) is an internal component used to supply the power to the components of a computer. Power supply is rated by the number of watts it generates.
Figure: Power Supply
Motherboard : The motherboard is the main circuit board of a microcomputer. It is also known as the main board or system board. It is the circuit board in which all the components are connected through cable within a personal computer. Many devices are connected with motherboard directly or indirectly. Motherboards usually provide the interface between the CPU memory and input/output peripheral circuits, main memory, and facilities for initial setup of the computer immediately after power-on.
Von Neumann Architecture
Mathematician John Von Neumann conceived a computer architecture which forms the core of nearly every computer system in use today. This architecture is known as Von Neumann architecture. It is a design model for the modern computers which has central processing unit (CPU) and the concept of memory used for storing both data and instructions. This model implements the stored program concept in which the data and the instructions both are stored in the memory. All computers share the same basic architecture which have memory, an I/O system, arithmetic logic unit (ALU) and control unit (CU).
Figure: Von Neumann architecture
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