UNIT-2 Classification of Computer 2.1        On the basis of working principle – Analog, Digital and Hybrid Computers. 2.2.On the basis of size – Super, Mainframe, Mini and Microcomputers. 2.3.On the basis of brand-IBM PC, IBM Compatible and Apple/Macintosh 2.4.Mobile Computing

Chapter 2 – Classification of Computer

Classification or types of computer

     The grouping or categorization of computer on the bases their different attributes (application, construction, size, work, capacity, speed, Brand, Model and operation) is known as classification of computer.

1.      Classification based on Work (or function or application)

On the basis of the technology that is used for the functioning of the computers, they can be divided in three categories: digital, analog and hybrid.

a)      Analog Computer

@ Analog computers work upon continuous data.

@ Analog computers measure physical magnitudes such as voltage, temperature, current and pressure.

@ It data is represented by physical variable whose magnitude is vary. It is not versatile. It is low accuracy.

@  Examples of analog devices as Speedo meter, thermo meter, Multimeter etc. Some of the popular analog computers are:-

ü  Seismograph used in geography to measure the earthquake.

ü  Speedo meter used in car and motorcycle for calculating their speed.

ü  Mental disease diagnostic device.

ü  In ICU (Intensive Care Unit) of a hospital and heartbeat, blood pressure pulse etc.

b)      Digital Computer

@ Digital computers work upon discontinuous data.

@ These computers work on binary digits 0 and 1.

@ It accuracy is high and fast process.

@ It is versatile.

@ Two types of digital computers:

ü  Special Purpose Computer – Digital Clock, Calculator

ü  General Purpose Computer – PC in computer lab

ü   

Different between analog and digital computer

Analog computer	Digital computer
i. it measures the continuous data.	i. it measures discrete data.
ii. It generate analog signal.	ii. It generate digital signal.
iii. It is slower then digital computer.	iii. It is faster.
iv. It has very low accuracy.	iv. It has very high accuracy.
v. It does single purpose work.	v. It does multi-purpose work.
vi. It has not programming possibility.	vi. It has high programming possibility.
vii. It is not versatile.	vii. It is versatile.
viii. It has less memory capacity.	Viii. It has high memory capacity.
ix. Example of speedometer.	ix. Example of IBM-PC.
x. It is a specific purpose.	x. It is a general purpose.

c)      Hybrid Computer

@ Hybrid computers are computers that comprise features of analog computers and digital computers.

@ The digital component normally serves as the controller and provides logical operations, while the analog component normally serves as a solver of differential equations.

@ It measures both continuous and discrete data.

@ It is commonly used in hospital to measure heart function, temperature, and vital signal of the patient. It is also used industry, scientific research, airplane, and so on. Some of the hybrid computers are FCM (flight management computer, EICAS (Engine indicator crew allot system) and jet plane, Electrocardiogram(ECG), Holter Monitoring machine, Ultra-sound machine, CT-scan machine etc.      

1.      Classification based on Size

      Supercomputer

@ Supercomputer is the most powerful, fastest, largest and expensive in the world.

@ Supercomputer is also known as number crunching.

@ Number of processor is 4 to 16.

@ Clock speed measure greater than 1000 MHZ.

@ It can also process millions of instruction per second..

@ Support multi-user.

@ Used 100 GB RAM and 1000 GB secondary disk.

@ Size is huge.

@ Supercomputer is widely used in government agency and international company.

@ Application: weather maps, construction of atom bombs, Movie animation, Seismography (earthquake prediction), military research, defense system, plasma and nuclear research, in encrypting and decoding sensitive intelligence information etc.

@ It can cost up to thousands of Dollars.

@  Some supercomputers are CRAY-i/ii/iii, CRAY-XMP, SX-2, HITACS-300, CYBER-205, and NEC-500 Etc.

     Mainframe computer

     Mainframe computer is smaller size, capacity and powerful than super computer but, lager capacity, powerful and size and expensive than mini & micro computer. They are used in Hospitals, for companies, banks, airline and railway, communication, reservation systems, census etc. They are also used in LAM, MAN, WAN networking.

@ Mainframe computer is also called Enterprise server.

@ They used number of processor is 1 to 4.

@ Clock speed is greater than 100 MHz.

@ Supports multi-users.

@ It can also process millions of instruction per second.

@ Less expensive than Supercomputer

@ Size is large.

@ Word length is 32 bits or 64 bits.

@ RAM capacity is 8 GB.

@ Mainframe computer can run multiple operating systems hence, they are called virtual machine.

@ IBM 1401 was brought for 2028 B.S census.

@ ICL 2950/10 was brought for 2038 B.S census.

@ Both computers are out-dated so that they kept in the museum of National computer center.

@ It can cost up to thousands of Dollars.

@ Examples are IBM 1404, ICL 2950/10, 1CL 39 series, IBM 4300 series, HP 9000 model 3705/300, HP 9000 model 8705/400 etc.

                                                       

      Minicomputer

           Minicomputer is also known as mid range computer because it has capacity between mainframe and microcomputer.  Minicomputer is smaller size, speed, powerful and storage capacity than supercomputer, mainframe computer and more than microcomputer.  The first minicomputer was launched digital equipment corporation (DEC). Minicomputers are used by government offices,  data processing, programming, desktop publishing fiels,industry, university, organization & other in LAN environment to facilities multiple users.

@ They are used single processor.

@ These computers are preferred mostly by small type of business personals, colleges etc.

@ It’s an intermediary between microcomputer and mainframe.

@ Clock speed is greater than 10 MHz.

@ Supports multi-users.

@ CPU speed is greater than 1 MIPS.

@ Size is medium.

@ Word length is 12 bits.

@ Minicomputer started in the 1958.

@ Examples are HP 3000, PDP-8, PDP-11, HP 9000, NECK, and PLESLE, VAX etc.                                                        

    Microcomputer/Personal Computer

          Microcomputer is the smallest, less powerful, chipset all of them. It is also known as home or personal computer. It is commonly found in home, office, schools, desktop etc. Microcomputer can communicate with LAN, MAN, &WAN with the help of communication device and modem or NIC card. Examples are IBM PC, IBM XT, IBM AT, IMB ps/2 etc.

             A microcomputer contains a (a central processing unit on microchip),in the form of read-only memory and random access memory ,  and a  housed in a unit that is usually called a motherboard .

v  Desktop computer: - They are used in single location, cheap, and have good storage. Examples include: apple, IBM

v  Laptop computer:/ notebook computer - Laptop computer is also known as notebook computer. They are smaller in size, more expensive and rechargeable. Examples include Apple, Acer, and Hewlett Packard (HP).

v  Notebook computers typically weigh less than 6 pounds and are small enough to fit easily in a briefcase. Principal difference between a notebook computer and a personal computer is the display screen. Many notebook display screens are limited to VGA resolution.

v  Hand-held computer PC (PDA): - Also called as palmtop or mobile device. They are smaller in size, have smaller display and input device is generally electronic stylus. Their storage capacity is small. Handheld computer is a pocket-sized computing device, typically having a display screen with touch input or a miniature keyboard. Also called a PDA (Personal Digital Assistant). Some manufacturers are trying to solve the small keyboard problem by replacing the keyboard with an electronic pen. Typically used as an appointment book, address book, calculator, and notepad.  Examples include Apple Newton etc.

v  Pocket computer: - A pocket computer is a small calculator-sized handheld programmable computer. It has only RAM maximum upto 1GB and Hard disk capacity is 80GB.                                            

3. Classification based on Model

  XT (Extended Technology)

@ The computer having 8086(16 bits) or 8088(8 bits) microprocessors are called XT computer.

@ XT computer have processing speed of 4.7 MHz.

@ The XT is old technology where used 4-bits microprocessor.

@ The XT technology only support CUI based operating system.

@ They had less storage capacity.

@ They were very slow.

@ The model refers to first Generation.

  AT (Advanced Technology)

@ This computer had 80286 microprocessor is called AT computer.

@ They are faster and have larger storage capacity than the XT computers.

@ They run latest versions of the software.

@ The higher capacity AT computer may have the micro processors 80386, 486 DX, 486 SX and above Pentium.

@ They used 1.2 MB floppy and 16 bits data bus.

@ They have processing speed more than 100 MHz.

@ AT supports GUI based operating system such as windows.

@ AT technology also supports 64-bits microprocess.

  PS/2 (Personal system/2)

@ IBM Company started manufacturing next model of computer in 1990, which is called PS/2. Most of the computers manufactured after 1990, including laptop computer being to those model.

@ The ps/2 is the new generation of personal computing. 2 stand for second generation.

@ They are faster and high storage capacity disk compare than AT and XT.

@ They can run latest version of computer software.

@ PS/2 technology is refinement version of AT technology.

@ PS/2 technology widely used in laptop as rechargeable devices.

@ In PS/2 technology, at first first runs OS/2 operation system then used windows operating system.

4.  Classification based on Brand

  IBM PC (International Business Machine Personal Computer)

@ The computer manufactured by IBM Company is called IBM computers.

@ It was established in USA in 1924.

@ In 1945, IBM Company started manufacturing mainframe computer, followed by minicomputers and microcomputers.

@ The mainframe, minicomputers and microcomputers manufactured by IBM Company are called IBM Company.

@ These computers are more reliable, durable and have better quality.

@ These computers are manufactured by IBM Company.

@ IBM manufactured mainframe computers followed by mini and microcomputers.

@ The microcomputer manufactured by IBM Company is called as IBM PC.

IBM Compatible

@ It has the same functional characteristics and the principles of IBM PC.

@ Some example of computer ATR, NEC, AST etc.

@ The IBM compatible is not the original IBM computer but their basic architecture is similar to IBM PC

@ All the software or program, which runs in IBM computer, can equally run in IBM compatible.

@ They are less expensive than original computer.

@ They are cheaper and their parts are easily available in the market.

@ Most of the microcomputers used in Nepal are IBM Compatibles.

   Apple /Macintosh                                                           

@ The computer manufacture by Apple Company having different architecture as compared to IBM computer is called Apple computer.

@ The apple company was established in USA in late 1970s.

@ It’s internal architecture totally differ than other own so that it requires own software

@ The apple company has manufacture now brand computer popularly is called Macintosh.

@ It is used for graphics designing.

@ They are quite expensive than IBM and IBM compatible.

@ The O/S and peripherals are completely different the IBM and IBM compatible.

Mobile Computing

Mobile Computing is a technology that allows transmission of data, voice and video via a computer or any other wireless enabled device without having to be connected to a fixed physical link. The main concept involves:

·        Mobile communication

·        Mobile hardware

·        Mobile software

Mobile communication

The mobile communication in this case, refers to the infrastructure put in place to ensure that seamless and reliable communication goes on. These would include devices such as Protocols, Services, Bandwidth, and Portals necessary to facilitate and support of the stated services. The data format is also defined at this stage. This ensures that there is no collision with other existing systems which offer the same service.

Since the media is unguided/unbounded, the overlaying infrastructure is more of radio wave oriented. That is, the signals are carried over the air to intended devices that are capable of receiving and sending similar kinds of signals.

Mobile hardware

Mobile hardware includes mobile devices or device components that receive or access the service of mobility. They would range from Portable laptops, Smartphones, Tablet Pc's, Personal Digital Assistants.

These devices will have receptor medium that are capable of sensing and receiving signals. These devices are configured to operate in full- duplex, whereby they are capable of sending and receiving signals at the same time. They don't have to wait until one device has finished communicating for the other device to initiate communications.

Above mentioned devices use an existing and established network to operate on. In most cases, it would be a wireless network.

Mobile software

Mobile software is the actual program that runs on the mobile hardware. It deals with the characteristics and requirements of mobile applications. This is the engine of that mobile device. In other terms, it is the operating system of that appliance. It's the essential component that makes the mobile device operate.

Since portability is the main factor, this type of computing ensures that users are not tied or pinned to a single physical location, but are able to operate from anywhere. It will incorporate all aspects of wireless communications.

Mobile Computing Classification

Mobile computing is not limited to Mobile Phones only, but also there are various gadgets available in the market helping mobile computing. They are usually classified in the following categories:

Personal Digital Assistant (PDA)

The main purpose of this device was to act as an electronic organizer or day planner that is portable, easy to use and. capable of sharing information with your with a computer systems.

PDA was an extension of the PC, not a replacement. These systems were capable of sharing information with a computer system through a process or service known as synchronization. Where both devices will access each other to check for changes or updates in the individual devices. The use of infrared and Bluetooth connections enabled these devices to always be synchronized.

With PDA devices, a user could; browsers the internet, listen to audio clips, watch video clips, edit and modify office documents, and many more services. They had a stylus and a touch sensitive screen for input and output purposes.

Smartphone

This kind of phone combines the features of a PDA with that of a mobile phone or camera phone. It has a superior edge over other kinds of mobile phones.

Smartphone have the capability to run multiple programs concurrently. These phones include high-resolution touch enabled screens, web browsers that can access and properly display standard web pages rather than just mobile-optimized sites, and high-speed data access via Wi-Fi and high speed cellular broadband.

The most common mobile operating systems (OS) used by modern Smartphones include Google's Android, Apple's iOS, Nokia's Symbian, RIM's BlackBerry OS, Samsung's Bada, Microsoft's Windows Phone, and embedded Linux distributions such as Maemo and MeeGo. Such operating systems can be installed on many different phone models, and typically each device can receive multiple OS software updates over its lifetime.

Tablet PC and I-Pads

This mobile device is larger than a mobile phone or a personal Digital Assistant and integrates into a touch screen and operated using touch sensitive motions on the screen. They are often controlled by a pen or touch of a finger. They are usually in slate form and are light in weight. Examples would include; Ipads, Galaxy Tabs, Blackberry Playbooks etc.

They offer the same functionality as portable computers. They support mobile computing to a far superior way and have enormous processing horse power. User can edit and modify document files, access high speed internet, stream video and audio data, receive and send e-mails, perform lectures and presentations among very many other functions. They have excellent screen resolution and clarity.

Advantages

• Portable: - Mobile computing also reduces transaction cost from one account to another  because of portability and easy communication access
•  Social interactivity: - It iv very useful tool for social interactivity that allows for data sharing and collaboration between users.
•  Content sensitivity: - It is also very useful tool for context sensitivity to gather and respond to real.
• Connectivity ability: - Its connectivity ability helps for communication of data in any environment.
• Quick service: - We can sell a product or give service in quicker time by using mobile computing.
•  Easy and quick enhancement: - Mobile computing is becoming very popular for streamline business processes for its promotion and enhancement easily and quickly.
• Ease of research: -Research has been made easier, since users will go to the field and search for facts and feed them back to the system.
•  Entertainment: -Video and audio recordings can now be streamed on the go using mobile computing. It's easy to access a wide variety of movies, educational and informative material.

Disadvantage

• Insufficient bandwidth: - If the user needs access to a network such as the internet on the go, they must resort to slow wireless WAN’s system primarily intended for telephone use.
• Security Standard: -When working mobile one is dependent on public network, requiring careful use of VPNs(Virtual Private Network).
• Power consumption: - Mobile computers must rely entirely on battery power.\
• Human interface with device: -These are still uncommon, screens are often too small. Keyboards are impractical, especially one-hand, and alternate methods such as speech or handwriting recognition require training.   

Computer science

UNIT-1 Introduction and Evolution of Computer 1.1.  Concept and Characteristics of Computer 1.2.  Application of Computers 1.3.  History of Computer: Mechanical Calculating era, Electro-Mechanical era, Electronic computers era. 1.4.  Generation of Computers: First, Second, Third, Fourth and Fifth Generation(AI) and its features, 1.5.  Computer speed and Measurement Unit

Unit-1 Introduction and Evolution of Computer

Definition of Computer

@ Computer is an advanced electronic device which takes raw data as input from the user and processes these data under the control of a set of instruction (program) and gives output.

@ A computer is an electronic device that manipulates information or data provided by user and process them which can be stored, retrieved at the time of necessity.

@ Computer is an electronic device that can perform mathematical calculations and logical operations at a very high speed.

@ Computer is an advance electronic device that must be completed IPO cycle.

@ A Computer is a collection of hardware and software components that help us to complete many different asks at enormous speed.

@ Computer is a programmable machine that stores and retrieves data and performs mathematical calculations as well as logical operations.

@ It can process both numerical and non-numerical (arithmetical and logical) calculations.

@ Computer is an electronic data processing device which

ü  accepts and stores data input,

ü  processes the data input, and

ü  Generates the output in a required format.

Functionalities of a computer

Any digital computer carries out five functions in gross terms:

ü  Takes data as input.

ü  Stores the data/instructions in its memory and use them when required.

ü  Processes the data and converts it into useful information.

ü  Generates the output

ü  Controls all the above four steps.

The term computer is derived from the Latin term ‘computare’, this means to calculate/count or programmable machine. The computer stands for:-

C = Command or Common. O = Operating or Obedient. M = Machine. P = Purpose or Provider. U = Useful or User. T= Technology or True. E = Education or Everything. R = Research or Right

IPO cycle

Input                                                                              

         Input is the raw information entered into a computer from the input devices. It is the collection of alphabets, digits, symbols, special character, graphics (picture or photo), audio, video etc. Input is always seen. Keyboard, Mouse, Joysticks, Scanner, Light pen, Touch pad, Digitizer etc are some of the input devices.

Process

         Process is operation of data as per given instruction. It is totally internal process of the computer system. CPU is the main processing device. Process is always unseen.

Output

         Output is the processed data (information) given by computer after data processing. We can save these outputs in the storage device for the future use. Monitor (screen), Printer etc are some of the output devices.

The main parts of Computer system

ü  CPU (Central Processing Unit).

ü  VDU (Visual Display Unit) or Monitor.

ü  Mouse.

ü  Keyboard.

ü  Printer.

ü  Scanner etc.

ü  UPS

Feature/ Characteristics of Computer.

ü  Speed.

ü  Electronic.

ü  Non-Intelligent.

ü  Word Length.

ü  High Storage Capacity.

ü  Automatic.

ü  Accuracy.

ü  Diligence.

ü  Versatility.

ü  Reliability.

ü  Multimedia supports.

Speed

 A Computer can perform very complex calculations at very enormous speed. One second is very long time period for the computer. Therefore, the computer speed varies from microsecond to nanosecond, even picoseconds.  Generally, the speed of computer is measured in terms of fraction of second.

• Second(s)-Second (1/1)                                                                                  -10^-0Hz
• Milliseconds – One thousandth of a second (1/1000)                                                -10^-3KHz
• Microseconds – One Millionth of a second (1/1000000).                              -10^-6MHz
• Nanoseconds – One billionth of a second (1/1000000000).                           -10^-9GHz
• Picoseconds – One trillionth of a second (1/1000000000000).                      -10^-12THz
• Femto second(fs)- One quadrillionth of second(1/1000000000000000)       -10^-15PHz

·         Alto second(As)- One of Femtosecond 1/10000000000000000000)                        -10-18EHz

Storage

A computer has the ability to store a large volume data permanently. User can use this data at any time. The storing capacity of computer is generally expressed in Bytes. Normally one byte stores one character of data. The storage capacity is measured in terms of:

0 or 1	1 Bit
4 Bit	1 Nibble
8 Bits or 2 Nibble	1 Byte
1 Byte	1 Character
1024 Bytes	1 Kilobyte(KB)
1024 kilo Bytes	1 Megabyte(MB)
1024 Mega Bytes	1 Gigabyte(GB)
1024 Giga Bytes	1 Terabyte(TB)
1024 Terabytes	1 Petabyte(PB)
1024 Petabytes	1 Exabyte(EB)
1024 Exabytes	1 Zeta Byte(ZB)
1024 Zetabytes	1 Yotta Byte (YB)

Accuracy

Computer always performs its tasks without making any mistake if the instruction is provided correctly. So the accuracy of computer is cent percent.

Versatility           

Versatile means ability to perform various tasks. A Computer has a wide range of application and is used in different fields such as education, science & technology, astronomy, business, entertainment, medicines etc.

Diligence

Computer is capable of doing the required tasks again and again without affecting its speed, accuracy and efficiency.

Reliability

 Computer output is generally very reliable, if the input data and instruction is correct. Incorrect data and unreliable programs give us computer errors and wrong results, the computer is 100% accurate, and it is reliable.

Automatic          

 Computer can be programmed to perform a series of complex tasks automatically. So, the computer has been used for quality control in industries. For example: If we can double click on Ms Word file that can automatically open & convert it into useful format.

Non-intelligent

Computer is a dumb machine and it cannot do any work without instruction from the user. So a computer cannot take its own decision as we can.

Word Length

Word Length refers to the number of bits that the CPU can process in parallel at a time. Modern processors, including embedded systems, usually have a word length of 8, 16, 24, 32, 64 bits, while modern general purpose computers usually use 32 or 64 bits. The power of computer depends upon the word length that makes the more powerful computer.

Electronic

Limitations of Computer

Although computer are very useful device and applied n various fields but there are limitations of computer.

@ Computer does not have its own intelligence. It is a dull machine.

@ Computers cannot memorize as long as they are no given the instruction to store in the secondary storage

@ Instructions are needed to perform any task.

Advantages of Computer

@ It is a reliable machine and performs the task with 100% accuracy rate.

@ Comparing with human being it is much faster.

@ It can be very useful while doing repeated tasks.

@ It is versatile as it can do many types of jobs once at a time.

@ They have large storage capacity, so we can store large amount of data for

Disadvantages of Computer

@ Computer is expensive and still not affordable.

@ Repair and maintenance is required frequently.

@ People are becoming too much dependent on computers.

@ Very difficult to maintain the privacy.

@ Skilled user is required to work with the computer.

@ It cannot be used on the dusty and the rough environment.

@ To increase unemployeement.

@ To increase laziness.

@ To damage our eyes.

@ Dangerous of electricity.

 Application of Computer

Computer is used in large areas such as banking, education, hospital, industries, research, hospital, data processing, science and engineering, offices, railways, advertisement, communication, library, simulation, weather forecasting etc.

a)      Banking & Financial Company - Computer are used in bank and financial company for electronic money transfer, statistical report, voucher, ledger, balance sheet etc.

b)      Education - Computer can be used as teaching learning tool, result processing, students' data processing, question preparation, handouts and note preparation etc.

c)      Industries - Industrial research, budgeting, process control all are computer based in modern industries.

d)     Hospital - In hospitals, computers are applied in medicine, surgery, research, diagnose disease etc.

e)      Science & Engineering - Computer is a strong tool for every branch of engineering such as civil, electrical, computer, aeronautic, ceramics, chemical etc.

f)       Advertisements - Computers are used for advertisement such as business advertisement, film advertisement. It is also used to make cartoon films, special effects and image processing.

g)      Communications - E-mail, e-fax, internet etc are computer based communications. The computer and Internet integration is the backbone of recent communication.

h)      Library - Computer software are used for the management of library. It is used for keeping books, borrowing books, updating the records etc.

Data processing

Data processing is the process of transforming data (raw material of information) into useful information by the computer is called data processing. During data processing the following operations take place.

v    Input and output operations.

v    Text manipulation and calculation operations.

v    Logical and comparison operations.

                                               Data and Information

Data	Information
Data is a collection of raw facts and figures about a person, place and things.	Information is processed data by the computer after data processing.
Data is unorganized.	Information is organized.
Data is not arranged.	Information is arranged.
Data is meaningless information.	Information is meaningful.
Data is input.	Information is output.
Examples: 2, (, &, ram, pen, bench etc.	Examples: Ram is a boy, Pen is writing tool. etc

History of Computers

The history of computer starts from 4000 years ago. History of computer means the gradual change in the concept over a long period of time. According to the technology and concept used on devices, we have three types of calculating devices:

• Early development mechanical devices
• Electro mechanical computers
• Electronic computers.

Mechanical Calculating Devices

a)      Abacus

• Created by Chinese about 3000 years ago.
• The first mechanical aid to calculations.
• Calculations are performed by manipulating the beads.
• It is a rectangular box, divided into two parts by mid bar, upper part is called heaven consists of two beads and each bead equal to value 5 and lower part is called earth, consists of five beads and each bead equal to value 1.

b)      Napier’s Bone

·         Napier’s bones is a multiplication tool invented in 1617 AD by mathematician Johan Napier of Scotland.

·         Multiplication tables were inscribed on strips of wood or bone.

·         Possible to perform calculations with two numbers.

·         It is mainly used for multiplication table.

·         He also developed the concept of logarithm (logarithm table) in 1614 AD

c)      Slide Rule

• Invented by William Oughtred (1574-1660), an English mathematician in 1620.
• An analog device used the principle of logarithms.
• Could perform simple multiplication and division problems.
• Consists of 2 graduated scales, during calculation time, small scale sliding over larger scale and the result was obtained by viewing the scale. 

d)     Pascaline

• Developed by Blaise Pascal (1623-1662) in 1642 to help his father’s tax work.
• It contains eight dials, gears and wheels.
• It was capable of performing additions and subtractions up to 8 digits.
• It could add and subtract by the movement of wheels, not used for division and multiplication.

e)      Stepped Reckoner

• Developed by Gottfried Wilhelm Von Leibniz (1646-1716), a German Mathematician & philosopher in 1671.
• It could evaluate square roots by series of stepped additions.
• The centerpiece of this machine was its stepped-drum gear design.
• Could perform all four of the basic arithmetic functions – addition, subtraction, multiplication and division.

f)       Difference Engine

• Designed by Charles Babbage (1792 – 1871) an English mathematician, in 1822.
• It could solve equations.
• This project could not be completed due to lack of funds.
• It is housed in the Science Museum, London and is till in perfect working order.

g)      Analytical Engine

• Developed by Charles Babbage in 1833.
• It had a ‘store’ for storing data and intermediate results.
• It had an output device to produce printed results.
• It had a unit for calculation called ‘mill’.
• All the modern computers are based on analytical engine (input-process-output).

h)      Hollerith Tabulator

• Developed by an American Dr. Herman Hollerith (1869-1926) in 1887.
• It used punched cards for input, output and instructions.
• This machine was used by American Department of Census to compile their 1890 census.
• In 1896, he founded the tabulating machine company which was renamed as IBM (International Business Machine) later.

Charles Babbage (1792-1871)

• A professor of mathematics developed a machine called Difference Engine in 1822.
• In 1833, he developed the Analytical Engine.
• He is known as the ‘Father of the Modern Computer’ as his invention Analytical Engine had far more of the characteristics of modern computers.

Lady Augusta Ada Lovelace (1816-1852)

• An English mathematician (daughter of English Poet Lord Byron) carried forward the work of Charles Babbage.
• She developed programs for performing mathematical calculation on the Analytical Engine.
• She was the first computer programmer.
• One programming language ‘Ada’ was named after her.

Electro-Mechanical Computers

a)      Mark-I

·         Designed by Howard Aiken (1900-1973), a Harvard engineer in 1937.

·         It was the first automatic electromechanical computer.

·         It was 51 ft. long, 8 ft. tall and 3 ft. wide having 18000 vacuum tubes.

·         It used instructions stored in paper tapes and punched cards.

·         It consists of 7 lakhs 50 thousands parts.

b)      ABC (Atanasoff-Berry Computer)

·         First electromechanical digital computer.

·         Built in 1937-1942 at Lowa State University by John V. Atanasoff and Clifford Berry.

·         It introduced the ideas of binary arithmetic and logic circuit.

·         It used punch cards as secondary storage.

Electronic Computers

a)      ENIAC (Electronic Numerical Integrator and Calculator)

·         Designed by Dr. John W. Mauchly and Dr. J. P. Eckert, completed in 1946.

·         It was built from 18,000 vacuum tubes, and 70,000 resistors.

·         Power consumption – 50,00,000 Kilowatt and floor space – 1,800 square feet.

·         It could add two numbers in 200 microseconds and multiplication of two numbers in 2800 microseconds.

b)      EDSAC ( Electronic Delay Storage Automatic Computer)

·         Designed by Maurice Wilkes at Cambridge University, mathematical laboratory in 1947.

·         It was the first operational stored-program computer.

·         It contains 3000 vacuum tubes and operated on 30 Kilowatt.

·         It used a mercury delay line storage system.

c)      EDVAC (Electronic Discrete Variable Automatic Computer)

·         Designed by J. Mauchly and J.P. Eckert at Pennsylvania University and was completed in 1950.

·         It included a stored-program, a central processor and a memory for both data and programs.

d)      UNIVAC (Universal Automatic Computer)

• Produced by Universal Accounting Company & set up by John Mauchly and J.P. Eckert in 1951.
• It consisted of magnetic tape for data input and output.
• It was the first general-purpose electronic digital computer designed for commercial use.

Computer Generation         

       A continues stage of computer who continue develop the computer system is called computer generation.  The generation of computer means the gap between the developments of the computer in terms of the technologies. Computer generation depends on the device and technology of computer hardware and software, timeline, cost, speed, size, accuracy and reliability. There are totally five computer generations known till date.

    First Generation of Computer (1946-1959)

ü  Major components – Vacuum Tubes

ü  Very slow, large in size, consumed a lot of electrical power.

ü  The operating speed was measured in terms of milliseconds.

ü  Storage capacity was too small only 1 to 4Kb.

ü  Used stored program concept.

ü  For input: - Punched cards.

ü  For output: - paper, punched cards.                

ü  Language: - Supported machine language only

ü  Storage: - Punched paper tape, magnetic tape etc.

ü  Generate lots of heat.

ü  Programming mainly at the hardware level.

ü  Non-portable

ü  Need of A.C.

ü  Few 1^st Gen. Computers – Mark – I, ENIAC, EDVAC, EDSAC, UNIVAC etc.

Second generation computer (1959-1965)

ü  Major components – Transistors instead of vacuum tube

ü  Smaller and faster than first generations computers.

ü  The operating speed was measured in terms of microseconds.

ü  Magnetic tapes were used as secondary storage media.

ü  Consumed less electricity, Generated less heat as compared to first generation computers

ü  Still very costly

ü  A.C. needed

ü  Supported machine and assembly languages

ü  For technology or electronic circuitry: - Transistor.

ü  For input: - Punched cards.

ü  For output: - paper.      

ü  Language: - Assembly language.

ü  Storage: - magnetic cores, magnetic storage cores etc.

ü  Programming mainly at the hardware level.

·         Few 2^nd Gen. Computers - LEO Mark III, ATLAC, UNIVAC I, ICL 1901, IBM 1620, 1400, 7000,CDC 1604, 3600, 160A, 3600,  Honeywell 800, 400 series etc.

Third generation computer (1965-1971)

ü  Major components – IC (Integrated Circuits) instead of vacuum tubes and transistor.

ü  Smaller size, Generated less heat, Faster, Lesser maintenance, still costly.

ü  High-level languages (FORTRAN-II TO IV, COBOL, PASCAL PL/1, BASIC, ALGOL-68 etc.) were used during this generation

ü  A.C needed.

ü  Consumed lesser electricity.

ü  Supported high-level language,

ü  Used high level language for giving instructions.

ü  For technology or electronic circuitry: - LSI, MSI

ü  For input: - Punched cards, keyboard.

ü  For output: - paper, monitor.                

ü  Language: - High level language.

ü  Storage: - Magnetic disks, magnetic tapes etc.

ü  Programming did not dependent on the hardware level.

ü  RAM and ROM were used for memory.

ü  High operating speed, multiprogramming, multiprocessing.

ü  Mainframe and minicomputer were introduced in this generation.

ü  Few 3^rd Gen. Computers - IBM 360 Series, ICL 1900 Series, VAX 1/780, IBM-360 series, Honeywell-6000 series, PDP(Personal Data Processor), IBM-370/168, PDP-8, PDP-11 series, CDC 7000, 7600, TDC-316, control data 3300, 6600 ,7600, Burroughs-6700 etc

Fourth generation computer (1975 – present)

ü  Major components: - microprocessor (VLSI).

ü  The size was greatly reduced.

ü  In this generation time sharing, real time, networks, distributed operating system were used.

ü  All the high-level languages like C, C++, DBASE etc., were used in this generation.

ü  No A.C. needed, Concept of internet was introduced

ü  Portable and reliable, Very small size, Pipeline processing

ü  For technology or electronic circuitry: - Microprocessor.

ü  For input: - keyboard, mouse, scanner, digitizer etc.

ü  For output: -monitor, printer, plotter etc.                

ü  Language: - High level language (non-procedural language).

ü  Storage: - Magnetic disks, magnetic tapes, optical disk, floppy disk etc.

ü  Programming did not dependent on the hardware level.

ü  First microprocessor 4004 was introduced by American Intel Corporation in1971.

ü  They have very high speed of processing; they are 100 % accurate, reliable, diligent and versatile.

ü  The size varies from desktop to laptop or palmtop.

ü  Few 4^th Gen. Computers – Pentium I/II/III/IV, HP 3033, APPLE II, DEC 10, STAR 1000, PDP 11, CRAY-1(Super Computer), CRAY-X-MP(Super Computer), IBM PC, Apple/Macintosh Microcomputer, IBM-3080, IBM system/370, UNVAC 1108, UNVAC 9000 series, HP-9000, HP-3000, AMD athelon, Cray 2 XMP,

Fifth generation computer (coming generation)

AI includes:

ü  Robotics, Neural Networks, Game Playing

ü  Development of expert systems to make decisions in real life situations.

ü  Natural language understanding and generation.

The main features of fifth generation are:

ü  Major components – ULSI (Ultra Large Scale Integration)

ü  ULSI technology: - Bio Chips (Organic Chips).

ü  Advancement in Parallel Processing

ü  Advancement in Superconductor technology, More user friendly interfaces with multimedia features

ü  All the high-level languages like C and C++, Java, .Net etc., are used in this generation.

ü  The concept of AI (Artificial Intelligence) has been introduced to take its own decision.

ü  Bio chips and Gallium Arsenide (GaAs) are used as memory devices.

ü  Extremely high-speed processing capability.

ü  Large uses of natural language processing and user friendly.

ü  Few 5^th Gen. Computers projects – ICOT program in Japan, MCC project in the USA etc.

ü  Availability of very powerful and compact computers at cheaper rates

ü  Examples: -Desktop, Laptop. Notebook, Ultra Book, Chrome Book

Some popular terms:

Vacuum Tubes

• The vacuum tube was invented by Lee De Forest in 1907.
• Lee De Forest was born o\in Council Bluffs, Lowa (USA) in August 26, 1873.
• It is a set of metal electrodes and grids contained in a glass or metal tube.
• The Vacuum tube was used in First generations computers.
• Formerly used for amplification and switching in electronic circuits, now used in CRT (Cathode Ray Tube).

Transistors

• Short for: transfer resistor
• It is a solid state semi-conductor device which can be used for amplification, switching, voltage stabilization, signal modulation etc.
• It transfers a signal from a low resistance to high resistance.
• It was invented in 1947 by three Bell Lab scientists John Bardeen, Walter Brattain, and William Shockley.
• Used in second generation computers as major components.

Integrated Circuits (IC)

• An IC is a circuit consisting of a large number of electronic components placed on a single silicon chip by a photolithographic process.
• Jack Kilby invented it in 1958.
• Used in third generation computers as major components.
• IC is used for a variety of devices, including microprocessor, audio and video equipment and automobiles.

Microprocessor

• The microprocessor is a computer processor built onto a single piece of silicon, known as a wafer or chip.
• First microprocessor is Intel 4004 developed by American Intel Corporation in 1971.
• Used in fourth generation computers as a major component.

Artificial Intelligence (AI)

A branch of computer science that refers to the use of computer in such a way that they are able to reason and draw, recognize voice and have language processing ability is called AI.

Biochip

The future device will be used in 5th generation computers, made of large organic molecules and a genetically engineered protein is called Biochip.