Unit-1 Introduction and Evolution of Computer
Introduction of computer:
            Computer is defined as an electronic digital and automatic machine which works on two state of current which is On and Off where on is represented by 1 and off is represented by 0. It takes input from user, process it, store it if necessary and give output in our desire form. It generates information by processing raw data according to the described sequence of instruction given by the user or operator. It is also called a multipurpose, programmable, electronic data processing device.

General Functions of computer:
Computer is an advanced electronic device that takes raw data as input from the user and processes these data under the control of set of instructions (called program) and gives the result (output) and saves output for the future use. It can process both numerical and non-numerical (arithmetic and logical) calculations.
Input (Data):
Input is the raw information entered into a computer from the input devices. It is the collection of letters, numbers, images etc.
Process is the operation of data as per given instruction. It is totally internal process of the computer system.
Output is the processed data given by computer after data processing. Output is also called as Result. We can save these results in the storage devices for the future use.
Computer data storage, often called storage or memory, refers to computer components and recording media that retain digital data. Data storage is a core function and fundamental component of computers.

Characteristics/Features/Capabilities of Computer:
1.      Speed: The speed of electronic computer is very fast because the signal can pass at the speed of electricity which is near to that of speed of light i.e. 2.997x108 m/sec. Thus millions of calculations can be done with in a fragment of second. The processing speed of microprocessor is generally measured in Millions of Instructions per second (MIPS).
Frequency (Hz) =1/time(in second)
Measuring units for processing speed in terms of frequency and time
Measuring units in frequency
Measuring units in Time
1 Hz (Hertz or 1x100 Hz)
1 second (1x100sec)
1 KHz (Kilo Hertz or 1x103 Hz)
1 milli second (1x10-3 Sec)
1 MHz (Mega Hertz or 1x106 Hz)
1 micro second (1x10-6 Sec)
1 GHz (Giga Hertz or 1x109 Hz)
1 nano second (1x10-9 Sec)
1 THz (Tera Hertz or 1x1012 Hz)
1 pico second (1x10-12 Sec)
1 PHz (Peta Hertz or 1x1015 Hz)
1 femto second (1x10-15 Sec)
1 EHz (Exa Hertz or 1x1018 Hz)
1 atto second (1x10-18 Sec)
1 ZHz (Zeta Hertz or 1x1021 Hz)

1.      Accuracy: The accuracy of a computer is consistently high, and every calculation is performed with the same accuracy i.e. 100% accurate results are always same as per design. The degree of accuracy of a particular computer depends upon its design. Sometimes errors can occur in a computer system due to inaccurate data or instructions fed by human or end users. If the error occurs due to the wrong input by the user then this type of error is called GIGO (Garbage In Garbage Out) and if the error occurs due to the malfunction of the computer hardware and this type of error is called Bug.
2.      Word Length: Digital computer operates on binary digits (bit), combination of 1 (one or high) and 0 (zero or low), which means all data or information are kept in computer or its memory in terms of 0's and 1's. Each digit of a binary number system is called BIT and a group of 8 bits are called BYTE. The number of bits that a computer can process at a time in parallel is called its word length. Commonly used word lengths are 8, 16, 32 or 64 bits and in super computer 128 bits is used. So longer the word length, the faster the computer is.
3.      Automatic: Being a programmable machine, modern computer can be programmed in such a way that it can perform a series of tasks automatically after it has been started. Modern digital computer does not need a human operator to execute different types of command.  
4.      Diligence: Unlike human beings, the computer never feels tired and bored to do a same task repeatedly. The computer can perform the same task with same speed and accuracy for a long time if it is provided the suitable environment and correct instruction. It is free from tiredness, weakness, lack of concentration and monotony.
5.      Reliability: computer system is particularly adept a lot of work without any mistakes and tiredness. That's why, they are widely used everywhere because of their reliability.
6.      Versatility: Computer can perform different tasks depending upon the different program fed to it, is known as versatility. It has a wide range of application areas i.e. it can do many types of jobs at the same time. Some of the application areas of computers are in education, business, office-automation, bank, medical diagnosis, science and technology. So, it is versatile in nature.
7.      Storage Capacity: A computer can store a great amount of data. It has data storage area, called memory. Any data stored in the memory can be retrieved at any time and at very fast speed. The storing capacity of a computer is measured in terms of byte, kilobyte, megabyte, gigabyte, terabyte etc.
Storage unit conversion table
In Unit
1 Byte
8 bits
1 Kilobyte
1024 bytes
1 Megabyte
1024 KB
1 Gigabyte
1024 MB
1 Terabyte
1024 GB
1 Petabyte
1024 TB
1 Exabyte
1024 PB
1 Zeta byte
1024 EB
8.      Electronic: Computer can't work without electricity. It is composed of electronic components such as transistor, diode, resister that require electric power to work. So, computer is called electronic machine.
9.      Non-intelligent: Although the modern computer is much more fast, reliable, accurate and diligent than human being. Being an artificial machine, computer does not have commonsense and intelligence. As a result, computer can't think and decide like human beings. Many man-made programs have to be installed in computer to do various kinds of tasks. Hence, this device is a non-intelligence machine.

Applications of Computers:
            Although, the early computers were mainly use for mathematical calculations to predict impact of bombs, calculate some other numerical values etc. By the development in technology, modern computers have played an important role in society because they have been used in the various sectors of the society in order to make the human life more efficient and comfortable. Following are the main applications/fields of computer:
1.      Education: Computers has been used in education to help the students in their study and the teachers to organize and prepare their teaching materials and collect required information from the internet. Due to the availability of e-books in CD, DVD and in internet, computer has been very helpful and essential device for students and teacher for their better education. Besides that, computers are kept in educational institute for keeping student records, preparing the result sheet, examination process, accounting and printing different documents.
2.      Offices: Modern computers are very necessary and useful resources in offices. In offices, computers are used in preparing the reports, letters, notice, salary sheet, income and expenditure reports etc. so that efficiency and work speed of the employees will be improved. The term electronic office is used, when all work of the office is done using computers. The term office automation is used, when computers are extensively used for office work.
3.      Health and medical field: Computers have played a vital role in medical field as it has been used in hospital to help the doctors, nurses and technicians to diagnose diseases, getting information about patient, disease and drugs. Similarly, many computerized equipment such as CT Scan Machine, eye testing machine and many other computerized machines are used for experiment and disease diagnosis. Surgeon also sues the computerized device to get the correct information about the condition of patient.
4.      Business: In business sectors computer is mostly used in department mall, shops and other retail centers to process sale transaction. Usually an optical bar code reader is marked on most packets to be sold by merchants to identify them. In Point-to-sale (POS) terminal, the computer prints name of the item, rate, price, validated date and other details on the receipt and issues the receipt to the customer, then total amount to be paid.
5.      Communication: Communication is done by emails, chat, online, conferencing, e-fax throughout a computer network that connects a number of computers or workstations with the help of internet. In communication computers are used to view and post news on computer bulletin board system (BBS), for electronic shopping, banking and brokerage and to get information services.
6.      Bank: Nowadays all the banks use computer for general-purpose computations, to handle transactions, to maintain ledger, to issue fixed deposit receipts, to make withdrawals and deposits to customers, to provide online service to customers who want to perform bank transactions from terminals and to answer customers regarding their balance. The large volume of cheque received every day in banks is processed by computers. These days, banks provide 24 hours ATM service, where user can withdraw their money anytime from ATM machine by using the ATM card.
7.      Industry: In industry, computer is extensively use for automatic control of machines, process, measurement and display of electrical and physical quantities. For example, automatic control of temperature of a heating system, speed of a motor, voltage of generator, pressure of boiler, testing of products, all are microprocessor based computer system. If any fault occurs on any part or the system, it immediately alarm and disconnect the faulty part from the healthy part of the system.
8.      Military: In military computers are used in defense purposes. Sophisticated weapons are being widely used in military operations with refined microprocessor-based control systems. These are modern tanks, missiles, fighter planes. Computer memory holds the detailed map of target area; photographs of the target area are taken and compared with stored map before it hits the target.
9.      Aviation: In aviation computer stores all necessary information regarding ticket reservation, such as flight number, flight route, flight distance, number of seats available for each flight in each class, ticket fare. It also stores information regarding persons who has already reserved. The person sitting at the counter gets information immediately whether seat on a particular date, in a particular flight is available or not. It is also used in air traffic control system to control landing and takeoff or airplanes to minimize any accidental risk.
10.  Robotics: Robot is computer controlled programmable machines composed of mechanical body, and optical sensors to provide eye-vision. A robot contains one or more microprocessors to control its action. In robotics it is used to perform works such as dancing mankind device, walking, moving, placing devices in right places, spray painting, welding, packing and placing huge amount of cartons. Robots are used in hazardous places, where man cannot work.
11.  Graphics: In graphics, computers are used to draw drawings, graphics and pictures. Adobe Photoshop, Corel Draw etc. packages are used to draw sophisticated drawings in multi-color in minutes. Graphics package is also used to recognize picture, process images, draw picture and finally it can also be modified.
12.  Design and Research work: Scientific and engineering design and research work involve complex and massive computations. In many cases simulation is also required. Design of brides, towers, buildings, generators, motors, electrical transmission network, statistical analysis or molecular structure of complex proteins needs complex computations. Computer is suitable for both complex computations as well as processing of massive amount of data. These complex computations may not be possible by hand or calculator. Nowadays, computer is must for this type of work.
13.  CAD (Computer Aided Manufacture)/CAM (Computer Aided Design): Computer is also used to control production of certain engineering and chemical products. In mechanical industry, designers use CAD and prepare the design of machines and machinery parts. Integrated approach of CAM and CAD is also used. In integrated system there is a database which stores all data regarding design, drawings and specifications. CAD is a software package which helps design engineers and architects to design and prepare drawings.
14.  Desktop Publishing System: A desktop publishing package is more powerful than word processor package. The desktop publishing system includes computer and a number of peripherals with powerful software that can produce complete page layouts with pictures and text printed in a variety of attractive ways. Such pages are used in book design, manuals, bulletins, newsletters.
15.  Entertainment: Computers are widely used in entertainment sector. In a movie special effects are put with the help of computers to make the movie more realistic and more interesting. Film producers take the help of computers to make cartoon movies and animation films. Music composers use computers for composing music and to set various notes and tunes accurately. In radio stations and FM stations, computers are used to manage and play songs, advertisements etc. When you get bored, you can enjoy by listening to music and watching movies on computers.
Capabilities and limitations of computer:
Ø  Computer produces 100% accurate outputs, if correct data and instructions are provided.
Ø  It is faster in calculation than human.
Ø  It can perform complicated and difficult work at a high speed.
Ø  It is capable of permanently storing data and retrieving it whenever required.
Ø  It can perform repeated task with the same speed and accuracy.
Ø  Computer is non-intelligent (dull) machine. It cannot think and give the right decisions as human being.
Ø  It cannot operate without battery or electricity.
Ø  Failure in devices and wrong information by users make it unreliable.
Ø  It cannot memorize and recall as needed only store data in secondary memory.
Ø  It requires instructions to perform a task.
Advantages and Disadvantages of computer:
Ø  It is faster than human beings and any other devices ever invented.
Ø  It is always accurate and reliable than human.
Ø  It is versatile i.e. master in all types of work and fields like education, hospital, banks etc.
Ø  It can be used for communication among many users.
Ø  It never feels exhausted and tired like human being.
Ø  Computer can be used for computer crimes like hacking, creating and sending viruses etc.
Ø  It has increased dependency on machine.
Ø  It is still expensive so each and every people cannot afford the computer.
Ø  Repair and maintenance is required frequently.
Ø  Skilled manpower is required to work in the computer.

"Necessity is the mother of invention". The saying is true for computer also because computer were inbuilt as a result of man search for fast and accurate calculating device. It is due to the need and curiosity of man for faster way to calculate has led to develop a computer. Following are the major development in the history of computer from early calculating machine to modern high speed digital computer.

The Mechanical Era (Zeroth Generation)
A mechanical computer is built from mechanical components such as levers and gears, rather than electronic components. The most common examples are adding machines and mechanical counters, which use the turning of gears to increment output displays. More complex examples can carry out multiplication and division, and even differential analysis.
1.      ABACUS:
The abacus, also called a counting frame, is a calculating tool used primarily in parts of Asia for performing arithmetic processes during 5000 BC to 3000 BC. Today, abaci are often constructed as a bamboo frame with beads sliding on wires, but originally they were beans or stones moved in grooves in sand or on tablets of wood, stone, or metal. It has two parts, heaven and earth. The heaven consists of two beads, whereas the earth part consists of five beads to each rod. It could perform only addition and subtraction.
2.      John Napier and his rods (1550-1617 AD):
The Scottish mathematician John Napier first published the table of logarithms in 1614 AD and it was very useful in simplifying the multiplication of large numbers. He invented some bone rods, uses bones to demonstrate division by subtraction and multiplication by addition, according to principle of logarithm. These rods were made up of strips of bones on which numbers were carved and painted, that device was called Napier bone.
3.      William Oughtred and his Slide Rule (1575-1660 AD):
In 1620 AD, the English man William Oughtred invented a rectangular calculating device called slide-rule based on the principles of logarithm. It consists of two graduated scales, one of which slips upon the other. The scales are devised in such a manner that suitable alignment of one scale against the other makes it possible to find products and quotient of any numbers.
4.      Blaise Pascal and his calculator (1623-1662 AD):
A French mathematician Blaise Pascal developed mechanical calculating machine to assist his father in his accounting work. In this machine numbers were entered by dialing a series of numbered wheels each wheel having numbers from 0 to 9. For addition the wheel was moved into forward direction and for subtraction into the reverse direction. It could perform addition and subtraction up to 8 digits.  This mechanical calculator is called Pascaline.
5.      Baron Gottfried Wilhelm Von Leibniz and his Stepped Reckoner (1646-1716):
In 1671 AD, Leibniz modified the Pascaline machine and invented a first calculator Stepped Reckoner, which was able to perform automatic addition, subtraction, multiplication, division and could find out square root. Leibniz's machine used stepped cylinder each with nine teeth of varying lengths instead of wheels. It was called Leibniz-calculator or Stepped Reckoner.
6.      Joseph Marie Jacquard and his Jacquard loom and punch cards (1752-1834 AD):
The French textile manufacturer Joseph Marie Jacquard invented a mechanism for automated weaving cloths for the textile industry at Lyon in 1802 AD. This machine was used to automatically control weaving looms to facilitate the production of weaving cloth with complex patterns. This machine was controlled by punch-cards i.e. principle of present and absence of holes.
7.      Charles Babbage and his analytical engine (1791-1871 AD):
The English professor and mathematician Charles Babbage invented the Difference Engine at Cambridge University in 1822 AD. Theoretically, it can solve differential equations and calculate various mathematical function, logarithmic tables, polynomial and trigonometric functions. Later Babbage continued working on his difference Engine and developed new idea for constructing general purpose, fully programmable automated machine called Analytical Engine in 1833 AD. He invented the working principle of computers on which the modern computer was based.
The principal is as:
i.     The Store: A mechanical memory unit consisting of sets of counters wheels, which could store data and intermediate result in punched card like on jacquard loom.
ii.   The Mill: An arithmetic unit, which was capable of performing four basic arithmetic operations; addition, subtraction, multiplication and division.
iii. Control Unit: A mechanism having gears and shafts by which data and results were transferred between the store and mill.
iv.  Cards (Input / Output device):
Input: There are basically two types of cards, Operation cards and variable cards where operation cards selects one of four arithmetic operations by activating the mill to perform the selected function. The variable cards select the memory locations to be used by the mill for a particular operation.
Output: Output could be directed to a printer or punch card device or got in copper plate.
8.      Lady Augusta Ada Byron Lovelace (1815-1852 AD):
The English woman Lady Augusta created the instruction routines to be fed into the computer and she suggested to Charles Babbage writing a plan for how the engine might calculate using Bernoulli numbers and that plan is now regarded as the first computer program. She wrote the program for Babbage analytical engine so she was considered the first computer programmer and, a software language developed by the US Defense Department was named Ada in her honor in 1979 AD.
9.      George Boole and his Boolean algebra (1815-1864 AD):
The Irish mathematician George Boole developed a method of reducing statements of logic to algebraic statements, using a simple set of symbols. He interprets that algebraic statements in to Boolean algebra in terms of truth values, called the propositional calculus, form the basis of the digital processes in modern computers. His logic provides the basic idea of presenting the electronic circuits with binary input (0 or 1) and its output.
10.  Herman Hollerith and his tabulating machine (1860-1929 AD):
An American inventor Herman Hollerith also applied the Jacquard loom concept in computing and applies for patents for automatic punch-card tabulating machine in 1884 AD. He invented a machine known as tabulating Machine (TM) in 1886 AD. He used cards to store data and each punch on a card represented one number and combinations of punches represented a letter. 80 variables could be stored on a single card. His machine was first used to compute the U.S. census. Later his machine became International Business Machine (IBM). He was founder of IBM and founded in 1924 AD. in USA.
The Electro-Mechanical Era
1.      Mark-I:
A professor of Physics Howard H. Aiken designed a general purpose mechanical computer at Harvard University and IBM, while working on his doctorate in physics, in the year 1937 and the machine was called IBM Automatic Sequence Controlled Calculator (IBM ASCC) and later as Harvard Mark-I. It was relay based computer on the based on the concept of Charles Babbage's analytical engine principle. Later he modified Mark-I and made Mark-II by using 19000 valves.
Features of Mark-I
·         It used about 18 thousand vacuum tubes as main memory device with 7 lakhs 50 thousands parts.
·         It is about 51 feet long, 8 feet height and 3 feet wide i.e. bulky in size.
·         Technically it was very complicated machine, consumed huge amount of power and generated lot of heat during the operation.
·         The time taken for multiplication was about four seconds and for division was about eleven seconds.
·         The results were printed at the rate of one result per five seconds.
2.      ABC (Atanasoff Berry Computer):
In 1938 John J. Atanasoff and Clifford Berry designed ABC for solving systems of simultaneous equation. It used 18000 calves and other 45 valves for internal logic and capacitors for storage of electrical charges. It used punched cards as secondary storage.
3.      John Von Neumann (1903-1957 AD):
The Hungarian mathematician Jon von Neumann gave the idea of stored program computer in the sense that program is stored internally in the main memory of the computer along with its associated data in 1945. So he is called father of stored program. Before that modification of a program was not possible.
The electronic computers Era
1.      ENIAC (Electronic Numerical Integrator and Calculator):
In 1946, John W. Mauchly and J. Prosper Eckert developed ENIAC at Pennsylvania, USA. ENIAC was the first-popular general purpose electronic digital computer. It was very large machine weighing about 30 tons and containing about 17468 vacuum tubes, 70,000 resisters, 5 million soldered joins and it consumed 160 kilowatts. It took 200 microseconds for addition and 3 milliseconds to perform a 10 digit multiplication. It was first and last computer, which used decimal number system instead of binary system.
2.      EDSAC (Electronic Delay Storage Automatic Computer):
EDSAC was invented by Maurice Wilkes in 1949. It also used vacuum tubes. Although started after EDVAC, it was completed before EDVAC. So, it became the first stored program computer.
3.      EDVAC (Electronic Discrete Variable Automatic Computer):
It was developed by J.P. Eckert and J. Mauchly in 1952 and used for more school personnel and the Ballistics Research Laboratory of the USA Army, built a computer named EDVAC. The construction of EDVAC was supervised by John Von Neumann. It also used vacuum tubes and some internal storage.
4.      UNIVAC (Universal Automatic Computer):
It was developed by J.P. Eckert and J. Mauchly in 1961. It was the first computer manufactured for commercial use and general purpose digital computer. Before this, all the computers were used either for defense or census.

History of computer in Nepal:
·         In 2018 BS, an electronic calculator called 'Facet' was used for census.
·         In 2028 BS census, IBM 1401, a second generation mainframe computer was used.
·         In 2031 BS, a center for Electronic Data Processing, later renamed to National Computer Center (NCC), was established for national data processing and computer training.
·         In 2038 BS, ICL 2950/10, a second generation mainframe computer was used for the census.
·         Nowadays, probably each and every institutions like schools, colleges, business organizations, communication centers, ticket counters etc. are using computers.
·         Nepal government has started establishing information center in most of the village development committee, e-government, GIS mapping and so forth.
·         The election commission of Nepal has started electronic voting system.

Generation of computers:
            Generation in computer is a step in technology. It provides a framework for the growth of the computer industry. The generations are considered on the basis of architecture, languages, modes of operation etc. There have been great variations in size and cost of computer. Computer system belonging to one particular technological class is said to belong to a particular computer generation.

Generation (Period)
Key hardware technologies
Key software technologies
Key characteristics
Some representative systems
·   Vacuum tubes
·   Electromagnetic relay memory
·   Punched cards secondary storage
·   Machine and assembly languages
·   Stored program concept
·   Mostly scientific applications
·   Bulky in size
·   High unreliable
·   Limited commercial use and costly
·   Difficult commercial production
·   Difficult to use
·   IBM 701
·   Transistors
·   Magnetic cores memory
·   Magnetic tapes
·   Disks for secondary storage
·   Batch operating system
·   High-level programming languages
·   Scientific and commercial applications
·   Faster, smaller, more reliable and easier to program than previous generation systems
·   Commercial production was still difficult and costly
·   Honeywell 400
·   IBM 7030
·   CDC 1604
·   ICs with SSI and MSI technologies
·   Larger magnetic cores memory
·   Larger capacity disks and magnetic tapes secondary storage
·   Minicomputer; upward compatible family of computers
·   Timesharing operating system
·   Standardization of high-level programming languages
·   Unbundling of software from hardware
·   Faster, smaller, more reliable, easier and cheaper to produce
·   Commercially easier to use and easier to upgrade than previous generation systems
·   Scientific, commercial and interactive on-line applications
·   IBM 360/370
·   PDP-8
·   PDP-11
·   CDC 6600
·   ICs and VLSI technology
·   Microprocessors; semiconductor memory
·   Larger capacity hard disks as in-build secondary storage
·   Magnetic tapes and floppy disks as portable storage media
·   Personal computers
·   Supercomputers based on parallel vector processing and symmetric multiprocessing technologies
·   Spread of high speed computer networks
·   Operating systems for PCs with GUI and multiple windows on a single terminal screen
·   Multiprocessing OS with concurrent programming languages
·   UNIX operating system
·   C and C++ programming language
·   PC, Network-based, and supercomputing applications
·   Object-oriented design and programming
·   Small, affordable, reliable and easy to use PCs
·   More powerful and reliable mainframe systems and supercomputers
·   Totally general purpose machines
·   Easier to produce commercially
·   Easier to upgrade
·   Rapid software development possible
·   IBM PC and its clones
·   Apple II
·   TRS-80
·   VAX 9000
·   CRAY-1
·   CRAY-2
·   ICs and ULSI technology
·   Larger capacity main memory, hard disks with RAID support
·   Optical disks as portable read-only storage media
·   Notebooks, powerful desktop PCs and workstations
·   Powerful servers, supercomputers
·   Internet
·   Cluster computing
·   World wide web
·   Multimedia, Internet applications
·   Micro-kernel, multithreading, multicore OS
·   JAVA
·   MPI and PVM libraries for parallel programming
·   Portable computers
·   Powerful, cheaper, reliable and easier to use desktop machines
·   Very powerful mainframes
·   High uptime due to hot-pluggable components
·   General purpose machines
·   Easier to produce commercially
·   IBM notebooks
·   Pentium PCs
·   SUN workstations
·   IBM SP/2
·   SGI Origin 2000
·   PARAM supercomputers

Artificial Intelligence (AI):
            AI is the field of computer science which tries to improve computers by endowing them with some of the characteristics associated with human intelligence like capacity to understand natural language and to reason under conditions of uncertainty. It is software that attempts to imitate aspects of human behaviors like reasoning, communicating, seeing and hearing etc.
Characteristics of AI:
·         AI is manmade and its level of activity depends on the programming capability.
·         It has the potential to extend problem solving ability of a manager beyond his/her normal capabilities.
·         It is a mechanism that is not subject to human feelings like fatigue, worry etc.

Computer Speed and measurement unit:
            A computer is a very fast processing electronic device. It can do task calculations at extremely high speed in fact with the speed of light. When we talk about a computer's speed, we mean how fast it can do processing-turn data into information. Every microprocessor contains a system clock. The system clock controls how fast all the operations within a computer take place.
            Processing speeds are expressed in megahertz (MHz) with 1 MHz equal to 1 million beats (cycles) per second. There are several units, which are used to evaluate the speed of a processor. Although none of them is a perfect indication to evaluate the performance of a processor. It is measured by the number of instruction executed per unit time, such as million instruction per second (MIPS) in case of super scalar architecture processors. For a vector processor the speed is measured in the Million Floating Point Instruction per second such as Mega Floating Point Instruction per second (Mega FLOPs).

Frequently asked questions:
A] Short answer questions:
1. What are the application areas of computer? Explain in brief.                                              [2067]
2. Why is Charles Babbage known as ‘Father of the computer’?                                                [2062supp.]
3. Describe at least five ways in which information technology can help students studying subjects other than computing.                                                                                                                        [2062]
4. Write brief note on achievement of the computer scientist Howard Aiken.                           [2062]
5. Explain the evolution of computer describing the technologies used in different generations. [2059]
6. What do you mean by generation of computer? Explain the characteristics of third generation of computers.                                                                                                                               [2061]
7. Compare the distinctions between third and fourth generations of computer.                      [2060]
8. State the characteristics of fourth generation computers.                                                      [2064]
B] Long answer questions:
1. What are the application areas of computer? Explain in detail.                                           [2065]
2. Discuss about how the development of the PCs (Personal computers) has extended the use of computer at present days.                                                                                                    [2058]
3. Explain the different generation of computers.                                                              [2065, 2066]
4. What do you mean by generation of computer? Explain the technology used in different generation of computer.                                                                                                                               [2067]


Unit-2 Classification of Computer
            Computers are classified according to working principle, size, brand and model. A single computer can be microcomputer on the basis of size, IBM compatible on the basis of brand, AT on the basis of model and digital on the basis of working principle.

On the basis of working principle:
On the basis of working principle computers are classified in the three types:
1.      Analog Computer:
The computer which can process analog quantities (Continuous data) is called an analog computer. Analog computer operated by measuring rather than counting. These types of computers are used in scientific work, commercial and personal purpose. For example, Odometer, Speedometer, thermometer, seismograph, voltmeter, ammeter, pressure gauge etc.
Characteristics of analog computer:
i.                    Based on continuous varying data
ii.                  Measure only natural or physical values.
iii.                Used for special purpose
iv.                 Generally, no storage facility is available because they work on real time basis.
v.                   Accuracy of these types of computer is very less because of noise and filtering facility.
vi.                 Output of those signals is not well known by general public because they are in form of wave lines, curved lines or graphs.
2.      Digital Computer:
The computer which works on discrete data (discontinuous data, binary system or 0 and 1) is known as digital computer. Binary system is such system of numbering in which only 2 digits are used 0 and 1. Where 0 represents either OFF, False, No etc. and 1 represents ON, True, Yes etc. So the basic principle of this computer is either present or absence of electrical pulses in the signal. For example, IBM PC, Apple/Macintosh, IBM Compactible etc.  
Characteristics of digital computer:
i.                    Based on discrete data which are not continuous with time.
ii.                  Based on principle of logic 1 and 0 (high and low voltage).
iii.                Used for general purpose.
iv.                 They are more reliable because of less noise and filtering facility.
v.                   It has large memory capacity because the calculations are to be stored internally for future use and re-programming.
vi.                 It is multipurpose and programmable. So, it is of high cost and faster processing.
Difference between Analog and Digital computers
Analog computer
Digital Computer
These computers work with natural or physical values.
These computers work with digits.
It works upon continuous data.
It works upon discrete data.
It operates by measuring and comparing.
It operates by counting and adding i.e. it calculates.
Its accuracy is low.
Its accuracy is high.
Output is continuous.
Results are obtained after complete computation.
It is special purpose computer.
It is general purpose in nature.
No any or smaller storage capacity.
Larger storage capacity (memory).
Lower cost compared to digital computers.
Higher cost compared to analog computers.
Normally, it cannot be reprogrammed.
It can be reprogrammed.
For example: Plessey, odometer, speedometer etc.
For example: IBM PC, IBM Compatible and other desktop computers.
3.      Hybrid Computer
Hybrid means combination or cross-link of two or more types. So, as the name suggests, it is combination of analog and digital computers. It can perform the works done by analog computers as well as by digital computers. Examples of these types of computers are: computers used in hospitals, computers used in jet planes etc.
Characteristics of hybrid computers:
i.                    It is the combination of qualities of analog as well as digital computers.
ii.                  It can process both continuous and discrete data.
iii.                It has capability to convert one type of data into another.
iv.                 It is the special purpose machine.
v.                   It is mostly used in airplane, hospital, weather forecasting.
vi.                 It is usually has high cost compared to analog and digital computer.
On the basis of size:
On the basis of size computers can be classified into four groups.
1.      Super Computer
Super computer is the most powerful and fastest computer among digital computers. This is special purpose and capable to handle huge amount of calculations that are beyond human capabilities. It processes billions of instructions per second (BIPS) and more. It can resolve complex mathematical equations in a few hours, which would have taken a scientist with paper and pencil lifetime, or years using a hand calculator.

Super computers are used for highly calculation-intensive tasks such as weather forecasting, climate research, molecular modeling, physical simulations such as simulation or airplanes and other scientific and engineering research. For example CRAY X-MP/24, NEC-500, PARAM, ANURAG, Fujitsu VP-2600/10 etc.

2.      Mainframe computer:
Mainframe is large, powerful system. These are the largest computers on the basis of size. A centrally located CPU is connected with more than 100 terminals. They are designed for large-scale data processing. For example, IBM 1401, ICL 2950/10, ICL 39, CYBER 170 etc.
Characteristics of Mainframe computer:
i.                    Very large in size with approximately 1000 sq. feet area.
ii.                  Central processor, central administration.
iii.                More than 100 terminals, large capacity storage devices used.
iv.                 Fastest and most expensive system in comparison to contemporary machines.
v.                   General purpose computers.
vi.                 Used by large organization and governments for large scale data processing.
3.      Minicomputer:
These are the medium sized computers on the basis of size. A centrally located CPU is connected with around 50 terminals. Examples of these computers are: Prime 9755, VAX 7500, HCL, MAGNUM, DEC VAX etc.
Characteristics of minicomputer:
i.                    Medium sized computer occupying approximately 10 sq. feet of area.
ii.                  Around 50 terminals and large capacity storage devices than microcomputers but smaller than mainframes.
iii.                Used for general purpose.
iv.                 Used in medium sized organizations and corporations.
4.      Microcomputers:
A computer which is based on microprocessor is called microcomputer. It is small, low cost digital computer. It requires small space, can be placed on a table or even kept inside a briefcase. This computer has central processing unit on a single chip. It is mainly used in office, house, school, shop and stores. They are desktop, laptop, notebook, palmtop and PDAs.
Characteristics of microcomputers:
i.                    Smallest in terms of size, can be kept on top of desk (Desktop), on palm (palmtop), on the top of our lap (Laptop) and like a notebook.
ii.                  Speed is higher and cost lower.
iii.                Since a single user system is used, storage devices and memory are smaller sized.
Microcomputers are categorized as non-portable and portable category.

Microcomputer of non-portable categories is:
a.      Personal computer (PC)
PC is a small computer that easily fits on a normal sized office table. It is generally designed to be used by one person at a time. It is the most common computer and can be found everywhere like office, college, home, hospital and shop.
b.      Workstation computer (WC)
A workstation is a specialized computer which has more power and features than standard desktop PC. The processing power is typically 5 to 10 times more than a PC. They usually have larger main and backup memory, larger and high resolution monitor and accelerated graphics handling capabilities. They are used for modeling, animation and video editing.
Microcomputers of portable categories are:
a.      Laptop
Laptop is a portable computer which is easy to carry from one place to another. So, it is suitable for the person in move. It is a light weight but incorporate all basic features of computer like display, keyboard, trackball or pad, hard disk, floppy disk, CD, DVD drives. It generally uses LCD monitor. It can operate with AC or DC or both as well.
b.      Notebook
Notebook is also designed for the people in move. But it is smaller in size compared to laptop. It is a device with a reduced keyboard, screen, functionality, and software support than laptop.
c.       Tablet PC
Tablet PC looks similar to laptop or notebook but it is far more convenient to use. It is also a portable computer, but differs with respect to accessories, screen, the software used. It gives the opportunity of writing directly on the screen using a pen rather typing through keyboard. It has handwriting recognizing software, which recognizes the handwritten text and digitizes it.
d.      Palm Top
Palm top is also a portable PC which is the size of our palm. Unlike laptop and notebook, it has very small memory and features. It is mainly used for storing phone numbers, addresses, pictures and such other small data. It contains an electronic writing pad and a light-sensitive electronic pen for providing input.
e.      PDA (Personal Digital Assistant)
PDA is also a species of portable computer. It is much limited in terms of the task, it can perform. It contains facilities such as colored screen, scientific calculator, digital-diary for storing telephone numbers and addresses, web browser, cell phone for communication, audio-video and games.
Differences between Microcomputer and Super computer
Micro computer
Super computer
It is less powerful according to processing capabilities.
It is more powerful computer.
It is the smallest computer on the basis of size.
It is larger in size.
It is cheaper.
It is most expensive.
It can be handled by only one person.
It requires numbers of experts to operate.
It is used in office, house.
It is used in weather forecasting, scientific research.

On the basis of Brand:
On the basis of brand computers can be classified into following categories:
1.      IBM computers
IBM stands for International Business Machine. It is one of the largest computer and other electronic equipment manufacturing company founded by an American Herman Hollerith in 1924 AD. IBM computers are of two categories:
a.      IBM-PC
This computer is developed by IBM Corporation itself, so it is also called as branded or original IBM PC. It is expensive, durable and reliable than IBM compatible PC.
b.      IBM compatible PC
It is developed by the companies other than the IBM Company but uses the parts and principle of IBM. It is generally called as assembled or duplicate of IBM PC and is comparatively cheaper than the IBM PC.
Difference between IBM PC and IBM Compatible PC
IBM Compatible
IBM computer is developed by IBM company itself.
IBM compatible computer is developed by the company other than IBM but based on the principle developed by IBM.
It is generally called as branded or original PC.
It is generally called as assembled or duplicate PC.
It is usually reliable compared to IBM compatible.
It is usually less reliable compared to IBM PC.
It is generally expensive.
It is generally cheaper.

2.      Apple/Macintosh computers
Apple/Macintosh is also known as Mac computer. It is developed by Apple Corporation. The architecture of this computer is totally different than IBM, not only the hardware portion; it has its own software as well. Almost all software’s made for IBM machine doesn’t operate on Macintosh and vice-versa. It uses MAC operating system. It is usually used for animation and graphics designing so has very high primary memory (RAM).

On the basis of Model:
On the basis of model computers can be classified in to following categories:
1.      XT computer:
XT stands for extra or extended technology. It is an old technology with very slow processing speed. It is text based system with no GUI (Graphic User Interface). Input/Output (I/O) device was not flexible and is slower than present devices.
2.      AT computers:
AT stands for advanced technology. AT computer is faster in processing and can run both GUI based and CUI (Character User Interface). I/O devices are interactive, flexible and faster. It was a medium speed processing device.
3.      PS/2 computer:
PS/2 stands for personal system-2. It is the modification of AT computer, making the computer faster than AT. It was mostly used in laptops with rechargeable and battery operated system with faster and flexible I/O devices.

According to the purpose for which they are used computer are classified into two categories:
1.      General purpose computer:
General purpose computer is the ordinary computer which can be used for different tasks such as preparing documents, playing games, watching movies, using college accounting software, using Internet etc. Its software is usually designed by the user according to their need.
2.      Special purpose computer:
A computer which is used for particular work only, is called a special purpose computer. This computer is usually programmed in the manufacturing stage itself for doing this work. It cannot be programmed and used for other works. Example: ATM (Automatic Teller Machine), Cash billing machine etc.

Mobile computing:
It is a generic term describing one’s ability to use technology while moving, as opposed to portable which are only practical for use while developed in a stationary configuration. It is a computing device used in transit. Mobile computing can be done by two devices:
a.      Internet tablet:
An Internet tablet is an internet appliance. It does not have much computing power and its application suite is limited, so cannot replace a general purpose computer. Internet tablets typically feature an audio and video player, a web browser, a chat application and a picture viewer.
3.      Smart phone:
A smart phone is a PDA with integrated cell-phone functionality. Current smart phones have a wide range of features such as audio/video player, camera, internet browser, Wi-Fi, Bluetooth, touch screen etc.

Frequently asked questions:
1.      Short answer questions:
a.      Compare and contrast analog and digital computers with appropriate examples. [2057]
b.      Differentiate between analog and digital computer.                                          [2060/2065]
c.       What are super computers? Explain their applications in real life situation.     [2061/2067]
d.      Compare mini and mainframe computers in terms of speed, memory and storage.
e.      Write short notes on:
i.                    Microcomputer [2058/2062]
ii.                  Super computer [2058]
iii.                Analog computer [2062]
iv.                 IBM PC and IBM compatibles [2063]
v.                   Digital computers [2063]



  1. nice but aru chapter ko pani chahiyo sir

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