TyroCity: Computer Notes

Number System

TyroCity.com — Sat, 12 Jul 2014 05:41:42 +0000

Conversion Techniques

1. Decimal to
a. Binary

/2 (Integer Part)
*2 (Decimal Part)

b. Octal

/8 (Integer Part)
*8 (Decimal Part)

c. Hexadecimal

/16 (Integer Part)
*16 (Decimal Part)

2. Binary to
a. Octal

Table (3-bit)

b. Decimal

*2n For eg. (1011)2 =1*23+0*22 +1*21+1*20

c. Hexadecimal

Table (4-bit)

3. Octal to
a. Binary

Table (3-bit)

b. Decimal

*8n For eg. (2341)8 =2*83+3*82 +4*81+1*80

c. Hexadecimal

Construct table of:
- Octal-Binary (3Bit)
- Binary-hexadecimal (4Bit)

4. Hexadecimal to

a. Binary

Table (4-bit)

b. Octal

Construct table of:
- Hexa-Binary (4Bit)
- Binary-Octal (3Bit)

c. Decimal

*16n For eg. (12A8)2 =1*163+2*162 +10*161+8*160

1’s and 2’s Complement

9’s and 10’s Complement

Computer Science Grade-11 2069

TyroCity.com — Sun, 18 Aug 2013 05:41:42 +0000

Candidates are required to give their answers in their own words as far as practicable. The figures in the margin indicate full marks.

Full Marks:- 75
Pass Marks:- 27
Time:- 3hrs.

Group A
Long answer questions

Attempt any three questions. 3×10=30

What is an operating system? Explain the functions of operating system.
What is memory in the computer system? Explain primary and secondary memory.
What is programming? Differentiate between compiler and interpreter.
What is Boolean algebra? Describe AND gate, OR gate, NOT gate and NAND gate symbol and Truth Table.

Group B
Short answer questions
Attempt any nine questions. 9×5=45

Why computer is known as versatile and diligent device? Explain.
What is mobile computing? Explain. Or Differentiate between analog and digital computer.
Convert (110111101)2 binary number into octal number.
What is BUS in terms of computer architecture? Explain.
Differentiate between Impact and Non-impact printers with examples.
What is internet? Write down the uses of internet. Or Explain the features of word processor.
What is web page? List the features of web page. Or Write down the advantages and disadvantages of DBMS. (Old)
What is CPU? Write down the functions of CPU.
Explain the types of programming errors with examples.
Subtract (1100)2 from (1111)2 using 1st and 2nd complement method.
Write short notes on:
- Modem
- Trackball

Computer XI Questions

TyroCity.com — Sun, 18 Aug 2013 05:41:42 +0000

Questions

Model Question for Computer Science Class 11

TyroCity.com — Sun, 18 Aug 2013 05:41:42 +0000

GRADE : 11
FOR : 2070
Time : 3hrs
F.M. : 75
P.M : 27

Group A (Long Answer Question)
Attempt ALL the questions. [3 × 10 = 30]

Draw a well-labeled diagram of typical architecture of a computer system and explain the main function of Control Unit and ALU. [4+3+3] 2.a. What is an operating system ? Explain any three function of an operating system. [1 + 6] 2.b. The “WiMP” environment is much more user-friendly, why ?

OR
2.a. What is cell addressing and explain different types of cell addressing used in spreadsheet. [5]
2.b. Write a tag to design your personal web page to link photo family, background and banner page using frame. [5]

3.a. Define flowchart and pseudocode. Explain their significance in programming. [5]

3.b. Write a pseudocode to accept any three numbers and output the largest among them. [5]

Group B (Short Answer Questions)
Attempt any NINE questions. [9 × 5 = 45]

Classify the computers according to their generation based on the technology used. [5]
Differentiate between analogue and digital computer, explain with examples. [5]
What do you mean by number system? Why do digital computers use binary numbers for their operation ? [2 + 3]
Convert these numbers. [5]
- (126)10 = (?) 2
- (11011)2 = (?) 10
- (57)8 = (?) 2
Perform following operations.
- 1011 – 1001
- 1110 + 1110
State the Demorgan’s theorem and verify it. [5]
What are logic gates? Construct the truth table of NOR operation. [5]
Write short notes on (any two) : [5]
- IDE
- SCSI
- Wave Camera
What are uses of internet ? Write any five search engine name. [5]
Differentiate between System Software and Application Software with examples. [5]
What are DPT features in MS-Words? Write three features of Presentation Packages. [2 + 3]
Write an algorithm and flowchart to print the word “Hello” ten times using “while loop” [5]

Communication And Computer Network

Computer 11 Notes — Sun, 08 Apr 2012 05:41:42 +0000

Introduction to communication and computer network

Today computer is available in many offices and homes and therefore there is a need to share data and programs among various computers with the advancement of data communication facilities. The communication between computers has increased and it thus it has extended the power of computer beyond the computer room. Now a user sitting at one place can communicate computers of any remote sites through communication channel. The aim of this chapter is to introduce you the various aspects of computer network.

Objectives

After going through this lesson you will be in a position to:

explain the concept of data communication
understand the use of computer network
identify different components of computer network
identify different types of network
explain communication protocols
understand what is internet and email and its uses in modern communication
appreciate the use of satellite communication.

Data communication

We all are acquainted with some sorts of communication in our day to day life. For communication of information and messages we use telephone and postal communication systems. Similarly data and information from one computer system can be transmitted to other systems across geographical areas. Thus data transmission is the movement of information using some standard methods. These methods include electrical signals carried along a conductor, optical signals along an optical fibers and electromagnetic areas.

Suppose a manager has to write several letters to various clients. First he has to use his PC and Word Processing package to prepare his letter. If the PC is connected to all the client’s PCs through networking, he can send the letters to all the clients within minutes. Thus irrespective of geographical areas, if PCs are connected through communication channel, the data and information, computer files and any other program can be transmitted to other computer systems within seconds. The modern form of communication like e-mail and Internet is possible only because of computer networking.

Basic elements of a communication system

The following are the basic requirements for working of a communication system.

A sender (source) which creates the message to be transmitted.
A medium that carries the message.
A receiver(sink) which receives the message.

In data communication four basic terms are frequently used. They are:

- Data: A collection of facts in raw forms that become information after processing.
- Signals: Electric or electromagnetic encoding of data.
- Signaling: Propagation of signals across a communication medium.
- Transmission: Communication of data achieved by the processing of signals.

Communication protocols

You may be wondering how do the computers send and receive data across communication links. The answer is data communication software. It is this software that enables us to communicate with other systems. The data communication software instructs computer systems and devices as to how exactly data is to be transferred from one place to another. The procedure of data transformation in the form of software is commonly called protocol.

The data transmission software or protocols perform the following functions for the efficient and error free transmission of data.

Data sequencing: A long message to be transmitted is broken into smaller packets of fixed size for error free data transmission.

Data routing: It is the process of finding the most efficient route between source and destination before sending the data.

Flow control: All machines are not equally efficient in terms of speed. Hence the flow control regulates the process of sending data between fast sender and slow receiver.

Error control: Error detecting and recovering is the one of the main function of communication software. It ensures that data are transmitted without any error.

Data transmission modes

There are three ways for transmitting data from one point to another

1. Simplex: In simplex mode the communication can take place in one direction. The receiver receives the signal from the transmitting device. In this mode the flow of information is Uni.-directional. Hence it is rarely used for data communication.

2. Half-duplex: In half-duplex mode the communication channel is used in both directions, but only in one direction at a time. Thus a half-duplex line can alternately send and receive data.

3. Full-duplex: In full duplex the communication channel is used in both directions at the same time. Use of full-duplex line improves the efficiency as the line turn-around time required in half-duplex arrangement is eliminated. Example of this mode of transmission is the telephone line.

Digital and analog transmission

Data is transmitted from one point to another point by means of electrical signals that may be in digital and analog form. So one should know the fundamental difference between analog and digital signals. In analog signal the transmission power varies over a continuous range with respect to sound, light and radio waves. On the other hand a digital signal may assume only discrete set of values within a given range. Examples are computer and computer related equipment. Analog signal is measured in Volts and its frequency in Hertz (Hz). A digital signal is a sequence of voltage represented in binary form. When digital data are to be sent over an analog form the digital signal must be converted to analog form. So the technique by which a digital signal is converted to analog form is known as modulation. And the reverse process, that is the conversion of analog signal to its digital form, is known as demodulation. The device, which converts digital signal into analog, and the reverse, is known as modem.

Asynchronous and synchronous transmission

Data transmission through a medium can be either asynchronous or synchronous. In asynchronous transmission data is transmitted character by character as you go on typing on a keyboard. Hence there is irregular gaps between characters. However, it is cheaper to implement, as you do not have to save the data before sending. On the other hand, in the synchronous mode, the saved data is transmitted block by block. Each block can contain many characters. Synchronous transmission is well suited for remote communication between a computer and related devices like card reader and printers.

Following are the major communication devices used to day.

Wire pairs: Wire pairs are commonly used in local telephone communication and for short distance digital data communication. They are usually made up of copper and the pair of wires is twisted together. Data transmission speed is normally 9600 bits per second in a distance of 100 meter.

Coaxial cables: Coaxial cable is groups of specially wrapped and insulted wires that are able to transfer data at higher rate. They consist of a central copper wire surrounded by an insulation over which copper mesh is placed. They are used for long distance telephone lines and local area network for their noise immunity and faster data transfer.

Microwave: Microwave system uses very high frequency radio signals to transmit data through space. The transmitter and receiver of a microwave system should be in line-of-sight because the radio signal cannot bend. With microwave very long distance transmission is not possible. In order to overcome the problem of line of sight and power amplification of weak signal, repeaters are used at intervals of 25 to 30 kilometers between the transmitting and receiving end.

Communication satellite: The problem of line-sight and repeaters are overcome by using satellites which are the most widely used data transmission media in modern days. A communication satellite is a microwave relay station placed in outer space. INSAT-1B is such a satellite that can be accessible from anywhere in India. In satellite communication, microwave signal is transmitted from a transmitter on earth to the satellite at space. The satellite amplifies the weak signal and transmits it back to the receiver. The main advantage of satellite communication is that it is a single microwave relay station visible from any point of a very large area. In microwave the data transmission rate is 16 giga bits per second. They are mostly used to link big metropolitan cities.

In-text questions 1

1. What is communication protocol?

2. What is the difference between asynchronous and synchronous transmission?

3. State whether True or False

The basic requirements for working of a communication system are sender medium and receiver.
Electric or Electromagnetic encoding of data is called Transmission.
In full duplex the communication channel is used in both directions at the same time.
Analog signal is measured in Volts and its frequency in Hertz
The technique by which a digital signal is converted to analog form is known as modulation.

Computer network

A computer network is an interconnection of various computer systems located at different places. In computer network two or more computers are linked together with a medium and data communication devices for the purpose of communicating data and sharing resources. The computer that provides resources to other computers on a net
work is known as server. In the network the individual computers, which access shared network resources, are known as workstations or nodes.
Computer Networks may be classified on the basis of geographical area in two broad categories.

Local area network (LAN)
Wide area network (WAN)

Local area network

Networks used to interconnect computers in a single room, rooms within a building or buildings on one site are called Local Area Network (LAN). LAN transmits data with a speed of several megabits per second (106 bits per second). The transmission medium is normally coaxial cables.

LAN links computers, i.e., software and hardware, in the same area for the purpose of sharing information. Usually LAN links computers within a limited geographical area because they must be connected by a cable, which is quite expensive. People working in LAN get more capabilities in data processing, work processing and other information exchange compared to stand-alone computers. Because of this information exchange most of the business and government organizations are using LAN.

Major characteristics of LAN

Every computer has the potential to communicate with any other computers of the network
High degree of interconnection between computers
Easy physical connection of computers in a network
Inexpensive medium of data transmission
High data transmission rate

Advantages

The reliability of network is high because the failure of one computer in the network does not effect the functioning for other computers.
Addition of new computer to network is easy.
High rate of data transmission is possible.
Peripheral devices like magnetic disk and printer can be shared by other computers.

Disadvantages

If the communication line fails, the entire network system breaks down.

Use of LAN

Followings are the major areas where LAN is normally used

File transfers and Access
Word and text processing
Electronic message handling
Remote database access
Personal computing
Digital voice transmission and storage

Wide area network

The term Wide Area Network (WAN) is used to describe a computer network spanning a regional, national or global area. For example, for a large company the head quarters might be at Delhi and regional branches at Bombay, Madras, Bangalore and Calcutta. Here regional centers are connected to head quarters through WAN. The distance between computers connected to WAN is larger. Therefore the transmission medium used are normally telephone lines, microwaves and satellite links.

Characteristics of WAN

Followings are the major characteristics of WAN.

1. Communication facility: For a big company spanning over different parts of the country the employees can save long distance phone calls and it overcomes the time lag in overseas communications. Computer conferencing is another use of WAN where users communicate with each other through their computer system.

2. Remote data entry: Remote data entry is possible in WAN. It means sitting at any location you can enter data, update data and query other information of any computer attached to the WAN but located in other cities. For example, suppose you are sitting at Madras and want to see some data of a computer located at Delhi, you can do it through WAN.

3. Centralized information: In modern computerized environment you will find that big organizations go for centralized data storage. This means if the organization is spread over many cities, they keep their important business data in a single place. As the data are generated at different sites, WAN permits collection of this data from different sites and save at a single site.

Examples of WAN

1. Ethernet: Ethernet developed by Xerox Corporation is a famous example of WAN. This network uses coaxial cables for data transmission. Special integrated circuit chips called controllers are used to connect equipment to the cable.

2. Aparnet: The Aparnet is another example of WAN. It was developed at Advanced Research Projects Agency of U. S. Department. This Network connects more than 40 universities and institutions throughout USA and Europe.

Difference between LAN and WAN

LAN is restricted to limited geographical area of few kilometers. But WAN covers great distance and operate nationwide or even worldwide.
In LAN, the computer terminals and peripheral devices are connected with wires and coaxial cables. In WAN there is no physical connection. Communication is done through telephone lines and satellite links.
Cost of data transmission in LAN is less because the transmission medium is owned by a single organization. In case of WAN the cost of data transmission is very high because the transmission medium used are hired, either telephone lines or satellite links.
The speed of data transmission is much higher in LAN than in WAN. The transmission speed in LAN varies from 0.1 to 100 megabits per second. In case of WAN the speed ranges from 1800 to 9600 bits per second (bps).
Few data transmission errors occur in LAN compared to WAN. It is because in LAN the distance covered is negligible.

Network topology

The term topology in the context of communication network refers to the way the computers or workstations in the network are linked together. According to the physical arrangements of workstations and nature of work, there are three major types of network topology. They are star topology, bus topology and ring topology.

Star topology

In star topology a number of workstations (or nodes) are directly linked to a central node (see, Fig. 4.3). Any communication between stations on a star LAN must pass through the central node. There is bi-directional communication between various nodes. The central node controls all the activities of the nodes. The advantages of the star topology are:

It offers flexibility of adding or deleting of workstations from the network.
Breakdown of one station does not affect any other device on the network.

The major disadvantage of star topology is that failure of the central node disables communication throughout the whole network.

Bus topology

In bus topology all workstations are connected to a single communication line called bus. In this type of network topology there is no central node as in star topology. Transmission from any station travels the length of the bus in both directions and can be received by all workstations. The advantage of the bus topology is that:

It is quite easy to set up.
If one station of the topology fails it does not affect the entire system.

The disadvantage of bus topology is that any break in the bus is difficult to identify.

Ring topology

In ring topology each station is attached nearby stations on a point to point basis so that the entire system is in the form of a ring. In this topology data is transmitted in one direction only. Thus the data packets circulate along the ring in either clockwise or anti-clockwise direction. The advantage of this topology is that any signal transmitted on the network passes through all the LAN stations. The disadvantage of ring network is that the breakdown of any one station on the ring can disable the entire system.

In-text questions 2

1. Differentiate between LAN and WAN.

2. What are the different types of network topology?

3. State True or False

Networks used to interconnect computers in a single room, rooms within a building or buildings on one site are called Wide Area Network (WAN).
The term Wide Area Network (WAN) is used to describe a computer network spanning a regional, national or global area.
The speed of data transmission is much higher in WAN than in LAN.
In star topology a number of workstations (or nodes) are directly linked to a central node.
The advantage of the bus topology is that, If one station of the topology fails it does not affect the entire system.

Internet

The Internet is a network of networks. Millions of computers all over the world are connected through the Internet. Computer users on the Internet can contact one another anywhere in the world. If your computer is connected to the Internet, you can connect to millions of computers. You can gather information and distribute your data. It is very much similar to the telephone connection where you can talk with any person anywhere in the world.

In Internet a huge resource of information is accessible to people across the world. Information in every field starting from education, science, health, medicine, history, and geography to business, news, etc. can be retrieved through Internet. You can also download programs and software packages from anywhere in the world. Due to the tremendous information resources the Internet can provide, it is now indispensable to every organization.

Origin of internet

In 1969 Department of Defense (DOD) of USA started a network called ARPANET (Advanced Research Projects Administration Network) with one computer at California and three at Utah. Later on other universities and R & D institutions were allowed to connect to the Network. APARNET quickly grew to encompass the entire American continent and became a huge success. Every university in the country wanted to become a part of ARPANET. So the network was broken into two smaller parts MILNET for managing military sites and ARPANET (smaller) for managing non-military sites. Around 1980, NSFNET (National Science Foundation Network) was created. With the advancement of modern communication facilities, other computers were also allowed to be linked up with any computer of NSFNET. By 1990 many computers were looking up to NSFNET giving birth to internet.

How internet functions

Internet is not a governmental organization. The ultimate authority of the Internet is the Internet Society. This is a voluntary membership organization whose purpose is to promote global information exchange. Internet has more than one million computers attached to it.

E-mail

E-mail stands for electronic mail. This is one of the most widely used features of Internet. Mails are regularly used today where with the help of postage stamp we can transfer mails anywhere in the world. With electronic mail the service is similar. But here data are transmitted through Internet and therefore within minutes the message reaches the destination may it be anywhere in the world. Therefore the mailing system is excessively fast and is being used widely for mail transfer.

In-text questions 3

What is internet?
What is e-mail?
How does internet function?

What you have learnt

In this lesson we discussed the importance and modes of communication through computers. Computers can communicate with one another through computer networking. There are two types of computer network: LAN and WAN. We discussed about the physical arrangements of computer and peripherals in network topology. There are three types of network topology: star topology, bus topology and ring topology. Also we discussed about Internet and e-mail.

Terminal questions

What is computer Network? What are its main objectives?
Differentiate between analog and digital transmission of data.
Explain in brief different communication media.
What is the difference between simplex and full-duplex transmission?

Feedback to in-text questions

In-text questions 1

1. The data communication software instructs computer systems and devices as to how exactly data is to be transferred from one place to another. The procedure of data transformation in the form of software is commonly called protocol.

2. In asynchronous transmission data is transmitted character by character as you go on typing on a keyboard. On the other hand, in the synchronous mode, the saved data is transmitted block by block.

True
False
True
True
True

In-text questions 2

1. LAN is restricted to limited geographical area whereas WAN covers great distance. In LAN the computer terminals and peripheral devices are connected with wires and coaxial cables whereas in WAN communication is done through telephone lines and satellite links. The speed of data transmission is much higher in LAN than in WAN.

2. There are three major types of network topology. They are star topology, bus topology and ring topology.

False
True
False
True
True

In-text questions 3

1. The Internet is a network of networks. Information in every field starting from education, science, health, medicine, history, and geography to business, news, etc. can be retrieved through Internet.

2. E-mail stands for electronic mail. Through e-mail we can transfer data anywhere in the world within seconds.

3. Internet is not a governmental organization. The ultimate authority of the Internet is the Internet Society. This is a voluntary membership organization whose purpose is to promote global information exchange.

Computer XI Notes

Computer 11 Notes — Sun, 08 Apr 2012 05:41:42 +0000

General

Introduction to Computer

Classification of Computer

Language/Software

Language/Software

Communication and Computer Network

Communication and computer network

Generation of computer

Generation of computer

Classification of Computer

Number System

Boolean Algebra

Boolean Algebra

Computer System

Operating System

Programming Concept

Application Package

Spread Sheet

Features of Microsoft Excel

Presentation

Internet

Remaining/Extras:

Line Printer

Computer 12 Notes — Sun, 08 Apr 2012 05:41:42 +0000

It is an impact type printer. It can print a complete line of text at a time. It can’t print images and text of different size and font. It is expensive than non-impact. It is appropriate for continuous printing like printing mark sheet, bill, bank statement, etc. the different line printers are: chain printer, drum printer, band printer.

Merits:

It can be used for continuous printing.
It is faster than character printer.
It can print a complete line of text at a time.
It can print multiple copies at a time.

Demerits:

It can’t print images and text of different size and font.
Its printing quality is low.
It is slower and noisy.
It can print a single color.
It is expensive.

Programming Concept | Computer Science | HSEB Notes

Computer 11 Notes — Sun, 08 Apr 2012 05:41:42 +0000

Detailed notes to follow:

- Types of programming language

1. Low level language

Machine Language (1GL)
Assembly Language (2GL)

2. High level language

Procedural-Oriented Language (3GL)
Problem-Oriented (Fourth Generation) Language (4GL)
Natural (Fifth Generation) Language (5GL)

- Language translator

Assembler
Compiler
Interpreter

- Syntax and semetics

Syntax Error
Sematic Error
Run-Time Error

- Flowchart

System Flowchart
Program Flowchart

Web Page Designing | Computer Science | HSEB Notes

Computer 11 Notes — Sun, 08 Apr 2012 05:41:42 +0000

Web page designing

1. Some of the Terms

HTML
HTML Tag

Paired Tag
Singular Tag

2. Basic structure of HTML

3. HTML Tag for formatting document

Heading tag
Paragraph
SUP & SUB tag
Comment tag
Tag
Font tag
Ordered & unordered tag
Inserting image inserting hyperlink
Scrolling Tag
FRAME Design
FORM designing

Radio Button
Check Box
Submit and Resent Button
Drop Down List

4. CSS (Cascading Style Sheet)

Limitations and evolutions of computer

Computer 11 Notes — Sun, 08 Apr 2012 05:41:42 +0000

Chapter 1
Limitations and evolutions of computer

Characteristics / Features of Computer

Speed (Processing)
Accuracy
Reliability
Storage Capacity
Word Length
Diligence
Versatile
Automatic
Electronic
Non-intelligent

Application Areas of Computer

Education
Communication
Business
Transportation
Banking
Health, Medicine, hospital
Security, military
Industry
Scientific research
Entertainment
Weather Forecasting
Desktop Publishing
Designing
Satellite Controlling
Aviation

Applications of Computer

Storing and maintain records
Helping deaf and dump people to communicate
Controlling the process of production in industries
Translating text from one language to another
Transforming information from one place to another
Playing games at homes
Logging archaeological findings
Designing and launching missiles, rockets, etc.

Advantages of Computer

They are fast device which helps us save our time and money
It is an automatic device
It is a diligence device
It is versatile i.e. it can be used in many different fields with minimum changes to it
It is always accurate and reliable then humans
It has a vast space for data storage
It can be used for communication purpose

Disadvantages of Computer

It is machine dependent
Repair and maintenance is required frequently
Skilled manpower is must to work in computers
It is still unaffordable to every household due to its very high cost
It has been widely used for cyber crimes
Computer users become completely dependent upon computers and working without them will be very difficult
With the overwhelming use of computer, unemployment problems might be created in lack of proper policies

History of Computer (Some important ones are only discussed over here)
ABACUS

A Chinese abacus
The abacus, also called a counting frame, is a calculating tool used primarily in parts of Asia for performing arithmetic processes. 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. The abacus was in use centuries before the adoption of the written modern numeral system and is still widely used by merchants, traders and clerks in Asia, Africa, and elsewhere. The user of an abacus is called an abacist.

EDVAC

The EDVAC is the successor of the ENIAC. Made by the same designers: Mauchly and Eckert.

design by Mauchly and Eckert
This computer was called by acronym EDVAC (Electronic Discrete Variable Automatic Computer) and its public presentation was carried through in 1947
This machine should be able to hold any program in memory that was fed to it. This would be possible because EDVAC was going to have more internal memory than any other computing device at that time. In other words, it was a multipurpose computer.

The idea being that given a tube of mercury, an electronic pulse could be bounced back and forth to be retrieved at will–another two state device for storing 0s and 1s. This on/off switch ability for the memory was required because EDVAC was to use binary rather than decimal numbers, thus simplifying the construction of the arithmetic units.
Source

Charles Babbage (1791 – 1871)

Babbage was a British mathematician, an original and innovative thinker and a pioneer of computing.

Charles Babbage was born on 26 December 1791, probably in London, the son of a banker. He was often unwell as a child and was educated mainly at home. By the time he went to Cambridge University in 1810 he was very interested in mathematics.
After graduation Babbage was hired by the Royal Institution to lecture on calculus. Within two years he had been elected a member of the Royal Society and, with his Cambridge friends, was instrumental in setting up the Astronomical Society in 1820, the first to challenge the dominance of the Royal Society. From 1828 to 1839, Babbage was Lucasian Professor of Mathematics at Cambridge.
The 1820s saw Babbage work on his ‘Difference Engine’, a machine which could perform mathematical calculations. A six-wheeled model was initially constructed and demonstrated to a number of audiences. He then developed plans for a bigger, better, machine – Difference Engine 2. He also worked on another invention, the more complex Analytical Engine, a revolutionary device on which his fame as a computer pioneer now largely rests. It was intended to be able to perform any arithmetical calculation using punched cards that would deliver the instructions, as well as a memory unit to store numbers and many other fundamental components of today’s computers. The remarkable British mathematician Ada Lovelace completed a program for the Analytical Engine but neither it, nor Difference Engine 2, were finished in Babbage’s lifetime.
Babbage also worked in the fields of philosophy and code-breaking, as well as campaigning for reform in British science. He died at his home in London on 18 October 1871.

Joseph Marie Jacquard

Joseph Marie Charles (called or nicknamed) Jacquard (7 July 1752 (Lyon, France) – 7 August 1834 (Oullins, France)) played an important role in the development of the earliest programmable loom (the “Jacquard loom“), which in turn played an important role in the development of other programmable machines, such as computers.
The Jacquard loom is a mechanical loom that has holes punched in pasteboard, each row of which corresponds to one row of the design. Multiple rows of holes are punched on each card and the many cards that compose the design of the textile are strung together in order.

Computer Architecture

Computer 11 Notes — Sun, 08 Apr 2012 05:41:42 +0000

Computer architecture can be defined as the arrangement or construction or design of different components of a computer. It defines how the different components of the computer are connected with each other.

Different components of the computer are given below:

Input unit
Memory unit
CPU
Output unit

1. Input unit
Input Unit is responsible for providing data and instructions to the CPU. It accepts input, converts it into computer’s format and provides it to system memory.
Keyboard is the most common input device. Some other input devices include mouse, joystick, light pen, touch screen, scanner, webcam, and microphone, touch pad and so forth.

2. Memory unit
Memory unit is responsible for storing data and instructions either for a short or longer period of time. Memory is of two types:

Primary Memory/Main memory
Secondary Memory/Auxiliary memory

- Primary memory
Primary memory is used for storing data and instructions during processing. It is the only memory which is directly accessible to CPU. It is expensive, faster and used in small capacity.
Examples:
· RAM
· ROM
· Cache memory

- Secondary memory
It is the additional memory used for storing huge amount of data for a longer period of time. It is also used for transferring data from one computer to another. It is usually cheaper, slower and used in larger capacity. It is not directly accessible to CPU.
Examples: CD, DVD, Hard disk, pen drive, etc.

3. CPU (Central processing unit)
CPU is responsible for processing the inputs for generating the outputs. It controls all the component of the computer. CPU contains three sub-components. They are:

ALU
CU
Set of Registers

- ALU (Arithmetic and logic unit)
It performs arithmetic and logical operations. It performs all its task according to the control signal from CU.

- CU (Control unit)
CU is responsible for controlling all the components of the computer including input devices, output devices, memory devices and other components of CPU. It uses control signal for controlling.

- Set of registers
Register is a temporary memory present in CPU. It is used for storing data instructions while it is being processed by CPU. CPU contains registers like MAR, MBR, TR, etc.

4. Output unit
Output unit is responsible for providing the result after processing. It converts the output from computer’s format into user understandable format before providing it to the user. The outputs generated by the computer are of two types:

Soft copy output
Hard copy output

- Soft copy output

The output from monitor, speaker, projector, etc. is termed as soft copy output. User cannot touch or feel this output. This output remains with the user till the computer is in ON state. User can modify the output is required.

- Hard copy output
The output from printer and plotter is termed as hard copy output. User can touch or feel this output. After the output is generated, it remains with the user even if the computer is in OFF state. User cannot modify the output.

Classification of Operating System

Computer 11 Notes — Sun, 08 Apr 2012 05:41:42 +0000

1. Multiuser OS:
In a multiuser OS, more than one user can use the same system at a same time through the multi I/O terminal or through the network.
For example: windows, Linux, Mac, etc.
A multiuser OS uses timesharing to support multiple users.

2. Multiprocessing OS:
A multiprocessing OS can support the execution of multiple processes at the same time. It uses multiple number of CPU. It is expensive in cost however, the processing speed will be faster. It is complex in its execution. Operating system like Unix, 64 bit edition of windows, server edition of windows, etc. are multiprocessing.

3. Multiprogramming OS:
In a multiprogramming OS more than one programs can be used at the same time. It may or may not be multiprocessing. In a single CPU system , multiple program are executed one after another by dividing the CPU into small time slice.
example: Windows, Mac, Linux,etc.

4. Multitasking OS:
In a multitasking system more than one task can be performed at the same time but they are executed one after another through a single CPU by time sharing. For example: Windows, Linux, Mac, Unix,etc.
Multitasking OS are of two types:

Pre-empetive multitasking
Co-operative multitasking

In the pre-empetive multitasking, the OS allows CPU times slice to each program. After each time slice, CPU executes another task. Example: Windows XP
In co-operative multitasking a task can control CPU as long as it requires . However, it will free CPU to execute another program if it doesn’t require CPU. Exaample: windows 3.x, multifinder,etc.

5. Multithreading:
A program in execution is known as process. A process can be further divided into multiple sub-processers. These sub-processers are known as threads. A multi-threading OS can divide process into threads and execute those threads. This increases operating speed but also increases the complexity. For example: Unix, Server edition of Linux and windows.

6. Batch processing:
A batch processing is a group of processing system in which all the required input of all the processing task is provided initially. The result of all the task is provided after the completion of all the processing. Its main functions are:

Multiple task are processed
User cannot provide input in between the processing
It is appropriate only when all the inputs are known in advance
It requires large memory
CPU ideal time is less
Printer is the appropriate output device
It is old processing technique and rarely used at present

7. Online processing:
It is an individual processing system in which the task is processed on individual basis as soon as they are provided by the user. It has features like:

Individual task is processed at a time
User can provide input in between processing
It is appropriate when all inputs ate not known in advance
It doesn’t require large memory
CPU ideal time is more
Monitor is appropriate output device
It is modern processing technique and mostly used in present