Chapter 1 Computer and Communication
Computer and Communication Long Answer Type Questions (8 Marks)
Write in brief about the evolution of computer. (U. P. 2010, 17)
A computer is a high-speed electronic device that accepts data and instructions from the user, then processes the data accordingly to produce information as output. It is capable of performing arithmetic and logical operations on data. It also stores and executes set of instructions. Data is entered in the computer through some input devices like keyboard, mouse, etc. It is then processed by C.P.U. and the result is displayed through an output device like a monitor.
The invention of the computer has affected many areas of our life. In its early time, it was a very costly and rare machine, limited to scientific laboratories and research centres. It was difficult to work on and they were very bulky. Slowly, the technology improved and the size of the computer reduced as well as its working became easy.
Computers have completely altered the structure of a business, a large volume of accounting and record-keeping, data can be manipulated, organized, stored, retrieved and used for scientific purposes.
Nowadays, a computer is used in homes, offices, shops and almost every-where. It is used to do simple as well as the most difficult calculations. Every business, no matter big or small, is based on computers. Similarly, an organization without computer is hard to find. Computer has changed the world.
Evolution of Computer: The first mechanical calculator developed by Blaise Pascal acted as a model for modem computers. Since then many machines have been developed which have to lead the way to modem microcomputers. A series of a scientific breakthrough by many scientists have contributed to produce this electronic machine called the computer.
1. Abacus: Movable beads on a wooden frame constituted the first known calculating device. The abacus was used by the ancient Greeks and Romans.
2. Pascaline: The gear-driven machine capable of addition, subtraction and multiplication, considered as a first mechanical calculator, was invented by French mathematician Blaise Pascal in the year 1642.
3. Jacquard’s Loom: In 1801, a Frenchman named Joseph Jacquard perfected a loom that was controlled by the holes in cardboard punched cards. This machine gave an idea about storage.
4. Difference Engine: In 1822, Charles Babbage invented his first machine (Difference Engine). He designed it to calculate logarithm tables. A series of levers were used to enter the data and a device similar to the typewriter was used to print the output.
5. Analytical Engine: In 1833, it was developed by Charles Babbage to perform addition, subtraction, multiplication and division through the use of the stored program. First programmer lady Ada Augusta Byron Lovelace helped him in its developing.
6. Atanasoff-Berry Computer: This electronic machine was developed by Dr John Atanasoff in 1939 for certain mathematical equations. It was called Atanasoff-Berry Computer or ABC, after its inventor’s name and his assistant Clifford Berry. It used 45 vacuum tubes for internal logic and capacitors for storage.
7. Mark 1: In 1944, Dr. Howard Aiken developed a machine called an Automatic Sequence Controlled Calculator which was later named as Mark-I. It was the first electromechanical computer.
8. ENIAC: First fully electronic computer named ENIAC (Electronic Numerical Integrator and Calculator) was developed by Prosper Eckert and J.W. Mauchly in 1945. It used high-speed vacuum tube switching devices.
9. EDVAC: In 1946, Dr John Von Neumann used the principle of storing in 0 and 1 (Binary Digits) in place of earlier technologies and developed EDVAC with the new concept of ‘stored program’. ED VAC (Electronic Discrete Variable Automatic Computer).
10. UNIVAC: Universal Automatic Computer was developed by Eckert and Mauchly in the year 1951. It was the first commercial computer used by Electronic Corporation. Its memory was MDL (Mercury Delay Line).
11. PDP Series: The computer of this series was developed by DEC (Digital Equipment Corporation).
- PDP-1 → 1961 → 8 bit → 4 KB
- PDP-8 → 1965 → 16 bit → 16 KB
- PDP-11 → 1970 → 16 bit → 32 KB
12. Micro Computers: Intel is the No. 1 company in the microprocessor. The microprocessors developed by this company were the best for microcomputers, few of them are as follows:
- 8080 → 1974 → 8 bits
- 8085 → 1978 → 8 bits
- 8086 → 1980 → 16 bits
- 80286 → 1982 → 32 bits
- 80386 → 1985 → 32 bits
- 80486 → 1986 → 32 bits
13. Pentium Series: After 80486, Intel developed Pentium processors which are used almost in every computer nowadays.
- Pentium → 1993
- Pentium I → 1995
- Pentium II → 1997
- Pentium Mobile → 1998
- Pentium III → 1999
- Pentium IV → 2000
- Pentium Centrino → 2004
What are the different components of the Computer?
The main components of the computer system are as follows:
- Computer Hardware.
- Computer Software.
- Computer User.
Computers are made up of many electronic and electro-mechanical devices. The devices together are referred to as computer hardware.
Hardware is the physical components of the computer which are tangible and visible to the user. Hardware is mainly categorised into two parts:
- C.P.U. (Central Processing Unit),
The computer will be of no use if it is not communicating with the external world. For a computer, it is must to have a system to receive information from the outside world and must be able to communicate results to the external world. Thus, a computer consists of an Input/Output (I/O) System.
Input Unit: Input unit is a link between user and computer. It takes the input from the user and converts it into a form understandable by the computer. It consists of input devices attached to the computer which feeds the data and instructions into the computer. Examples of Input Devices :
- Light Pen
- Optical Character Reader (OCR)
- Magnetic Ink Character Reader (MICR), etc.
1. Keyboard: The Keyboard is one of the most common input devices for the computer. The layout of the keyboard is like that of the traditional QWERTY type-writer.
Different type of keys of a keyboard are as follows:
- Alphabetical keys (A to Z, a to z)
- Numeric keys (0 to 9)
- Function keys (FI to FI2)
- Special keys (@, !, +, -, <, =, etc.)
- Cursor control keys (space bar, →, ↓, ↑, etc.)
2. Mouse: A mouse is a pointing device used while display based package. It is a push-button control device that eliminates the need to type computer commands. Instructions are given by the user to the computer by pointing an arrow on the screen to a picture or word and then pushing the button on the mouse. The user moves the arrow on the screen by sliding the mouse across the desktop. It is used for selection, dragging, drawing, playing games, etc.
3. MICR: Today banks are issuing special types of cheques. These cheques have the cheque number printed by special magnetic ink. The cheque clearance is done using computers. There is a special device called a MICR. It directly reads the cheque number, bank code, branch code etc. and converts it in machine-readable form.
4. OCR: Optical Character Reader is an information processing device that converts typed or handwritten data in a form that the computer understands. Its speed ranges from 50 to 3000 characters per second.
5. Scanner: Scanner is used to convert photographs and other images from documents and drawing into electronic form. The scanner is used to scan the images and store them on the disk, as a file.
6. Light Pen: A light pen is an electronic device in the form of a photodiode, that allows the operator to identify a particular point or character displayed on the screen, and can be used alone or in conjunction with a keyboard to add, rearrange or delete information, modify images displayed on the screen.
It is a communication link between the computer and the user. The output unit consists of the output devices attached to the computer. The output devices help in the communication of data and information from machine to man.
The output devices help the computer to communicate with the user by converting the electric signals to human understandable signals. Examples of output devices:
- VDU (Visual Display Unit)
The output on the VDU is called soft copy output whereas the output on paper, which is produced on printers and plotters is referred to as hard copy output.
1. Monitor/VDU: Monitor is a device to interact with the computer. The messages from the computer are displayed on the screen of the monitor. It is the most common output device using a Cathode Ray Tube (CRT) to produce images. Images are formed by a collection of spots, each known as a pixel.
Classification of Monitors: Monitors can be classified based on:
(A) Resolution: The number of pixels that make up the screen
The examples are CGA (Colour Graphic Adapter), EGA (Enhanced Graphic Adapter), VGA (Video Graphic Array Adapter), SVGA (Super Video Graphic Array Adapter), CGA having the least resolution and SVGA the highest resolution.
(B) Colour Facilities:
Monochrome. Single colour display on a black background.
Colour monitors. Which can display multicolour outputs by combining red, green and blue in varying intensities?
2. Printer: A printer is a device that can record information permanently on paper in the form of printed copies.
Printers are mainly divided into two parts:
(i) Impact Printer: These printers print characters by striking the character against the inked ribbon, which leaves an impression on the paper. Impact printers are noisy and can be used to create carbon copies.
(a) Dot-Matrix Printer: This is one of the most popular printers used for personal computing systems. These printers are cheaper as compared to other technologies. Dot Matrix Printer uses impact technology and a print head containing banks of wires moving at high speeds against inked ribbon and paper. These printers form characters by building them up by dots. The character matrix (array of wires) are of 7’5, 7’7, 9’7, 9’9.
The speeds range from 40 cps (characters per seconds) to about 1000 cps.
(b) Line Printer: The line printer prints one line at a time. The speed of line printers is measured in lines per minute. The printing speed of these printers varies from 300-3000 lines per minute. The width of the line is 15 inches and the line has 96 to 160 characters. Different types of line printers are Drum printers, Chain printers and Band printers.
(c) Daisy Wheel: Daisy wheel printer contains a disk of metal or plastic and it has 96 characters on its petals. This disk is capable of rotating. A hammer hits the petal to print the character. Speed of the Daisy wheel printer is 20-100 characters per second. These printers cannot be used for longer duration and also these are very slow in functioning. The main feature of the Daisy wheel printer is that its printing is of superior quality.
(ii) Non-Impact Printer: Non-impact printers print characters without directly striking on the paper. Non-impact printers cannot create carbon copies. They are, however, very quiet.
(a) Laser Printer: This is a high quality, high speed, high volume technology which works in non-impact fashion on plain paper or pre-printed forms.
Printing is achieved by deflecting laser beam on to the photosensitive surface of a drum. The latent image attracts the toner (A special kind to ink) to the image areas. The toner is then electrostatically transferred to the paper and fixed into the permanent image. The speed of printing can range from 10 pages per minute to about 200 pages per minute. This technology is relatively expensive but is becoming very popular because of the quality, speed and noiseless operations.
(b) Ink-Jet Printer: Ink-Jet printers print by spraying a cont-rolled stream of tiny ink droplets (from a fine nozzle) accurately on the paper forming either dot matrix or solid characters. These are non-impact printers.
The typical speed ranges from 50 cps to above 300 cps. This technology has been used well for the production of colour printing and elaborate graphics.
3. Plotter: Plotter is an output device that is used to produce graphical outputs on the paper. It uses pens, either of a single colour or multi-colour to draw pictures. Engineering designs can be printed with good precision by making use of plotters.
There are two types of plotters:
- Drum Plotter,
- Flatbed Plotter.
Applications of Plotters:
- Computer-Aided Design (CAD).
- Map Drawing.
- Architectural Drafting.
- General Business Applications.
The system unit is a box-like case that houses the electronic components of the computer that are used to process data. The system unit is made of metal or plastic and is designed to protect the electronic components from damage. The electronic components and most storage devices reside inside the system unit and the other devices such as a keyboard, mouse, monitor are located outside the system unit.
It is the main printed circuit board in an electronic device, which contains sockets that accept additional boards. In a personal computer, the motherboard contains the bus, CPU, memory sockets, keyboard controller and supporting chips.
Chips that control the video display, serial and parallel ports, mouse and disk drives may or may not be present on the motherboard. If not, they are independent controllers that are plugged into an expansion slot on the motherboard.
Central Processing Unit (CPU)
CPU is the brain of a computer system. It consists of:
- Control Unit (CU),
- Arithmetic Logical Unit (ALU),
- Memory Unit (MU).
The parts of a CPU are connected by an electronic component referred to as a bus, which acts as an electronic highway between them. In order to temporarily store data and instructions, the CPU has special-purpose storage devices called as registers. The CPU of a modem computer is fully electronic. It is made up of millions of electronic components etched on to a number of silicon chips. These chips are all assembled on a printed circuit board called the Mother Board.
Functions of CPU: The main functions of the CPU are the following:
- To store data and instructions.
- To control the sequence of operations.
- To carry out the processing.
The CPU of a personal computer is mainly recognized by the microprocessor chip that it uses.
Microprocessor Chips: A microprocessor is assembled from thousands of tiny transistors, resistors and other electronic components. A typical microprocessor is fabricated on a single tiny chip of silicon and is combined with other elements. These other elements provide input and output connections, storage and control to form a complete microprocessor onboard.
In the 70’s, Intel engineers built the first microprocessor chip for a Japanese manufacturer of desk calculators. Subsequently, 8-bit data processing capabilities were developed in chips. In 1974, a personal-sized system was developed and called ‘ALTAIR 8800′ which used the Intel 8-bit microprocessor.
In the 80’s, the personal computer systems started being based on a 16-bit microprocessor. The most popular amongst these is IBM PC.
All 16-bit personal computers are also built around a few popular microprocessors. The Intel 8088 is found in IBM PC. Another popular microprocessor used in systems such as Apple, Cromemco and many other vendors is the Motorola’s 68000.
Intel 80286, 80386 and 80486 are 32-bit microprocessor chips.
Intel’s Pentium series is the latest 32-bit and 64-bit microprocessor chips.
The microprocessor is the brain of a computer system. It is the place where actual processing is done. It consists of :
- Control Unit
- ALU or Arithmetic Logic Unit
1. C.U. (Control Unit): It controls the movement of data and program instructions into, and out of the C.P.U. and to control the operations of A.L.U., C.U., fetches the instructions from the main memory into registers, decodes it and sends control signals to other components of the computer so that the appropriate actions are carried out. This is known as fetch executes cycle.
2. ALU (Arithmetic Logic Unit): The ALU performs all the arithmetic and logical functions, that is, it adds, subtracts, multiplies, divides and does comparisons. It also performs logical operations (AND, OR and NOT). These operations provide the facility of decision making through the computer. The result of a logical operation is either TRUE or FALSE.
A.L.U. only operates on data that is in the internal C.P.U. memory, also known as registers. C.P.U. memory, also known as registers. Registers are very fast, temporary storage whose functions are to receive and hold data. They are not accessible to the programmers.
3. Registers: A register is a special temporary location within the CPU. Registers very quickly accept, store and transfer data and instructions that are being used immediately. To execute an instruction, the control unit of the CPU retrieves it from main memory and places it into a register.
The number and types of registers in a CPU vary according to the CPU design. Their size (capacity) and number can affect the processing power of a computer system. In general, the “larger” is the register (the more bits it can carry at once), the greater is the processing power.
BUS: The term ‘bus’ refers to an electrical pathway through which bits are transmitted between the various computer components. Depending on the design of a system, several types of buses may be present.
The control bus is the pathway for all timing and controlling functions sent by the control unit to the other units of the system.
The address bus is the pathway used to locate the storage position in memory where the next instruction is to be executed or the next piece of data will be found.
Data bus is the pathway where the actual data transfer takes place.
What do you mean by memory? Explain in brief.
Memory: A computer system has storage areas, referred to as memory. The memory can receive, hold and deliver data when instructed to do so. Data that are being processed are held in Primary Memory, which is capable of sending and receiving the data at very high speeds. Secondary memory stores data not currently being used and operates more slowly, but it is capable of storing large volumes of data.
Primary Memory: Primary Memory consists of semi-conductor memory chips and is used to store data and programs currently in use. Each storage element of memory is directly (randomly) accessible and can be examined and modified without affecting other cells. Main memory can be volatile or non-volatile. Primary memory is classified into two groups:
(A) RAM (Random Access Memory),
(B) ROM (Read Only Memory).
RAM is read/write memory. It is a volatile memory. It stores the information as long as power is switched on and the information is lost when the power supply is switched off. RAM is of two types:
- DRAM: It needs constant refreshing in order for the stored data to be maintained.
- SRAM: It does not need refreshing. It is faster and expensive than DRAM.
Features of RAM: The main features of RAM are as follows:
- Data that needs to be processed and the instructions which are used for processing are held in the RAM.
- Each element of RAM is a memory location in which data can be stored. Each location has a unique address. Using this address, data can be directly retrieved or stored.
- Since RAM must hold the data to be processed and the instructions for processing, its size or capacity is one of the measures of the power of the computer.
Functions of RAM: The principal function of the main memory is to act as a buffer between the CPU and the rest of the computer system components.
Main memory is used for the following purposes:
- Storage of a copy of the main software program that controls the general operation of the computer. This copy is loaded into main memory when the computer is turned on. and it stays there as long as the computer is on.
- The temporary storage of a copy of application programs and instructions to be retrieved by the CPU for interpretation and executed.
- The temporary storage of data that has been input from the keyboard or another input device until instructions call for the data to be transferred into the CPU for processing.
Read-Only Memory (ROM): ROMs are the memories on which it is not possible to write the data when they are on-line to the computer. They can only be read. The ROMs can be used in storing programs provided by the manufacturer of computer for basic operations. ROMs are non-volatile in nature and need not be loaded in a secondary storage device.
ROMs can be written only at the time of manufacture. It is necessary, and also convenient, to have instructions stored in ROM. For example, if you are using a microcomputer with floppy disk drives, the more instructions in ROM. the fever diskettes you may have to handle.
The process of manufacturing ROM chips and recording data on them was more expensive than the process of producing RAM chips. As a result, manufacturers tended to record in ROM only those instructions that were crucial to the operation of the computer.
PROM, EPROM, EEPROM: In addition to ROM, three additional categories of non-volatile memory are used in some computer systems namely PROM, EPROM and EEPROM.
PROM: Programmable Read-Only Memory is a non-volatile memory which allows the user to program the chip with a PROM writer. The chip can be programmed once, thereafter it cannot be altered. Therefore, PROMs are more flexible than ROMs.
EPROM stands for Erasable Programmable Read-Only Memory. EPROM chips were developed as an improvement over PROM chips.
The EPROMs can be written electrically. It requires the erasure of whole storage cells by exposing the chip to ultraviolet light, thus brings them to the same initial state. This erasure is a time-consuming process. Once all the cells have been brought to the same initial state, then the EROM can be written electrically.
EEPROM stands for Electrically Erasable Programmable Read-Only Memory. EEPROMs are becoming increasingly popular as they do not require prior erasure of previous contents. It avoids the inconvenience of having to take chips out of the computer to change data and instructions. Instead, changes can be made electrically under software control. These chips are being used in point-of-sale terminals to record price-related data for products. The only disadvantage of EEPROM chips is that they cost more than regular ROM chips.
Secondary Memory: Secondary memory is also known as permanent memory as we can store data on it for future use. It is both read/write memory and consists of different storage devices known as secondary storage devices as follows:
(A) Magnetic tape: Magnetic tape allows large amount of data to be stored economically passes the devices write head, data is recorded by magnetising the iron oxide in different directions. While reading the iron oxide causes a current in the read head.
(B) Floppy disk: It is a plastic film coated with iron oxide metal and protected by a plastic jacket as cover that has an opening which allows the read/write head to retrieve or store data. The most common floppy disk now in use is the 3.5″ disk also known as micro floppy. Earlier floppies were of 5.25″ and 8″.
(C) Hard disk: It comprises at least one rigid disk protected by a strong and airtight casing. It contains disks, read/write head, access arms, servomotor and the electronic circuit board to control the disk operations. This is the most common secondary storage device having the highest storage capacity (2GB, 4GB, 10GB, 40GB….). It is fast and speeds of less than 10 microseconds are achievable.
(D) Optical disk: These are plastic disks handles more data in comparison to floppy disks. In Optical disk a light source is used to catch data patterns on the disks. Normally two laser lights are used; a weak to read data and stronger to write by burning the surface of the disk. Different types of optical disks are CD-R, CD-R/W, DVD.
Describe Software in brief.
Software: Software is one of the primary elements of a computer system. It is a set of computer programs, procedures and associated documentation related to the effective operation of a computer system.
The software’s are classified into the following categories:
- System Software,
- Utility Software,
- Application Software.
1. System Software: System software is programs that directly interact with the hardware. For example, when a file is to be saved on a disk, the system software sends the required instructions to perform this task. It provides the environment to write application programs.
The system software is written by computer professionals called System Programmers.
The system software is of two types:
- Operating System.
Translators: Instructions given to a computer in any language, have to be translated into machine code for the computer systems to execute the instructions. This work of translation is done by a Translator.
Translators can be classified as:
(a) Interpreters: Interpreters are the translators which are used to convert programming language into machine language for the purpose of execution line by line. It translates one statement at a time and executes it.
(b) Compilers: The compiler translates the whole program code (known as source code) and prints a list of errors which have to be corrected as a whole. Once the program is error-free, the executable code is generated.
(c) Assemblers: This software translates a program written in assembly language to machine code.
(ii) Operating System: An Operating System is a set of routine programs that are used to manage the operations of the computer.
The Operating System isolates the hardware from the user. The user communicates with the Operating System, supplies application programs and the data that are in a language and format acceptable to the Operating System and receives output.
Some of the popular operating systems are:
DOS, WINDOWS 95, WINDOWS 98, WINDOWS NT, WINDOWS Millennium, XP, OS/2, LINUX, UNIX.
2. Utility Software: A utility program is a type of system software that performs a specific task, usually related to managing a computer, its devices or its programs. Most operating systems include several utility programs.
Some of the utilities are described below:
(i) File Compression Utility: A file compression utility reduces or compresses the size of a file. A compressed file takes up less storage space on a hard disk or floppy disk, which frees up room on the disk and improves system performance.
When a compressed file is received, it must be uncompressed or unzipped to restore it to its original form. Two popular stand-alone file compression utilities are PKZIP and WinZip.
Disk Scanner: A Disk Scanner is a utility that detects and corrects both physical and logical problems on a hard disk or floppy disk. It also searches and removes unwanted files.
Windows 98/XP includes two disk scanner utilities:
- Scan Disk which detects and corrects problems.
- Disk Cleanup searches for and removes unnecessary files such as temporary files.
(ii) Disk Defragmenter: A disk defragmenter is a utility that reorganizes the files and unused space on a computer’s hard disk so that data can be accessed more quickly and programs can run faster.
When a computer stores data on a disk, it places the data in the first available sector on the disk. Disk defragmenter reorganises the file and unused space. Windows includes a disk defragmenter called Disk Defragmenter.
(iii) Uninstaller: An uninstaller is a utility that removes an application, as well as any associated entries in the system files. When you install an application, the operating system records the information that it uses to run the software in the system files.
If you attempt to remove the application from your computer by deleting the files and folders associated with that program without running the uninstaller, the system file entries remain.
(iv) Anti-virus: An anti-virus program is a utility that prevents v detects and removes viruses from a computer’s memory or storage devices. A virus is a program that copies itself into other programs and spreads through multiple computers. Viruses are designed to damage a computer intentionally by destroying or corrupting their data.
(v) Back-Up: This is used to back-up files on your hard disk. Files can be back-up to a floppy disk, a tape drive or another computer on the network. If the original files are damaged or lost, it can be restored from the backup.
(vi) Search Engine: It is used to search files or data from the disk quickly. It works randomly to give search results to the user as quickly as possible.
3. Application Software: Application software consists of programs designed to perform specific tasks for users.
Application software also called a software application, can be used for the following purposes:
- As a productivity/business tool.
- To assist with graphics and multimedia projects.
- To support household activities, for personal business, or for education.
- To facilitate communications.
Word Processor: Word Processor transforms a screen into ‘sheets of paper’ to be written on, and provides quick and accurate ways to create and revise business documents.
These packages allow:
Text to be written in document form.
Edit any part of a document.
Adjust the format of a document, such as margins, spacing, page numbers.
Save the entire document on a disk and retrieve it later.
Wordstar, MS-Word, Word Perfect, Page Maker.
Spreadsheets: A spreadsheet is a table consisting of rows and columns, and provides business professionals with a quick and accurate means of performing mathematical calculations involved in answering a question.
It performs various mathematical functions as well as logical and conditional operations in a quick and accurate manner.
Examples: Lotus 1-2-3, Quattro Pro, Excel, Multiplan.
Database Management System: Database Management System (DBMS) is a set of programs that manipulates a database by appending, deleting and modifying records. It is used to generate the queries, forms, reports etc. on the basis of some condition by using different records stored in it.
The two basic types of data management software are
- File management systems, for example, Dbase, Foxbase, FoxPro etc.
- Relational Database Management System, for example, Ingress, Oracle, Unify etc.
Graphics/Presentation Packages: This software is used to create slide transition, animation, etc. by using its advanced features. Most of the graphics or presentations are being prepared using this software.
PowerPoint, Corel Draw, Macromedia, Director.
Desk Top Publishing (DTP) Software: It is a software system that is used to produce attractive page layouts complete with pictures and text printed in a variety of styles, which is ideal for use in newspaper and magazine publishing companies.
Examples: Page Maker, Word, Corel Draw.
What are the different means of communication available in the modern age? Give their comparison also. (U. P. 2006, 12, 15, 19)
Communication Media: The medium (or media) is the matter or substance that carries the voice or data transmission. It can be copper (wire or coaxial cable), glass (fibre optical cable), or wave (microwave). A circuit (channel or line) is nothing more than the path over which data moves.
Communication media is of two types:
(A) Guided / Wired Media: In this type of media, wires are used.
It is further classified into three categories:
(1) Twisted Pair Cable:
Made of copper, coated with insulating material and continuously twisted throughout its entire length.
Twisted cable helps minimize the effects of noise or electromagnetic interference.
Relatively inexpensive and easy to install.
Low immunity of noise, narrow bandwidth.
Data rates up to 20 Mbps in LAN; 19.2 Kbps for long-distance communications over the telephone network.
Readily available in existing buildings.
Usage: Voice communication, Data communication e.g., telephone.
2. Coaxial Cable:
Consists of wire surrounded by the insulating layer, shielding layer and an outer jacket.
Quarter-inch or more in diameter, therefore, less flexible than twisted pair.
Less susceptible to noise but more expensive than twisted pair.
Wider bandwidth, more difficult to install/tap, more costly than twisted pair.
Data rate up to 150 Mbps.
Data Communication Video Transmission Voice Communication
Used extensively in LAN and relatively short distance (10 miles). For longer distance, repeaters may be necessary.
3. Fibre Optic Cable:
- One or more glass or plastic fibres are woven together to form the core of the cable. This core is surrounded by a glass or plastic layer called the cladding, which in turn is covered with plastic or other material for protection.
- The light source used is either LASER or light-emitting diodes (LED) whereas the detector is a photodiode.
- Low error rate, very high noise immunity, immunity to electrical and magnetic noise.
- Reduced size and weight (than copper or coaxial).
- The high cost of installation with special equipment.
- Very expensive, but maybe economical for high-volume application.
- Broad bandwidth.
- High data rate-over 2 Gbps possible.
- Voice Communication
- Video Communication
- Data Communication
- Networks using fibre-optic are called “Fibre Distributed Data Interface” (FDDI) often ring-based.
(B) Unguided/Wireless Media: In this type of media, wires are not used, means no physical connection.
Why are computer and communication used together? What are its advantages? Give their application. (U. P. 2004, 16, 17)
Communication: Communication is a process in which data is transferred from one place to another. The three components of communication are:
- Sender: where the information is sent.
- Receiver: to whom the information is sent.
- Medium: through which the information is sent.
A computer is an electronic machine which can perform a variety of tasks like:
- Text formatting
- Producing sound
- Creating graphics
- Show clippings, etc.
All the above tasks are needed in the process of communication and that is why a computer is one of the most popular devices used for communication. In computer, communication information is sent electronically.
Advantages of Computer Communication: There are the following advantages of computer communication:
- A user-friendly environment.
- Information can be sent in multiple ways.
- Information can be transferred in pictures, sound, text, etc. from the same place.
- Secured means of communication.
- It saves time as well as money.
Application of Computer Communication: There are the following applications of computer communication:
- E-mail: Electronic mail is one of the most popular applications of communication.
- Video-conferencing: People from far off places can organize meetings very easily.
- Chatting: Different persons from different places can exchange their thoughts at the same time.
- Information Distributor: Information available on different computers can be used.
Draw the basic model for primary communication. Explain the functions of each block. (U. P. 2007, 10)
What is a basic model of communication? Explain its various parts. (U. P. 2008)
Give a simple block-view of a primary communication system. Explain the working of each block in detail. (U. P. 2011)
Communication: Transferring the data from one place to another is known as “communication.” For this, computers are playing a very important role in today’s life. We can connect one computer to others in any part of the world very easily and computers are used to do fast and accurate communication.
Every communication system has the following important components:
1. Sender: It is an electronic device which is responsible for sending information e.g., Telephone, Computer, Mobile, etc.
2. Data Communication Device: It is a device which accepts the data from source sending device and converts it into such a form (analogue signal) that can be transmitted over communication channels e.g., computers with the modem.
3. Communication Medium: In order to transfer the information from one place to another “carriers are needed”, and in a computer network these carriers are generally of two types:
Guided Communication Medium: In this type of medium, wires are used to transfer the data and it is also known as wired media. It consists of:
- Twisted Pair Cable,
- Co-axial Cable,
- Fibre Optics Cable.
Unguided Communication Medium: This is wireless medium, hence, no wires are used. It is categorised into:
- Radio Waves,
- Microwave Waves,
- Satellite Communication.
4. Receiver: It is used to accept signals of the communication system and convert them in an understandable form. Generally, the receiver is a computer with a modem.
- TCP/IP (Transmission Control Protocol/Internet Protocol): TCP breaks up the data to be sent into packets. It guarantees that any data sent to the destination computer reaches it. IP is a set of conventions used to send packets from one host to another. It is responsible for routing the packets to a desired destination IP address.
- X.12: This protocol is used to establish the connection between companies to exchange important papers.
- X. 25: This protocol establishes the interface for common data network.
- HTTP: HyperText Transfer Protocol works on the internet to send and receive files from different locations.
Computer and Communication Short Answer Type Questions (4 Marks)
The Internet is a packet-switching network, data is transmitted by converting it into packets. This work is done by the set of rules or standard designs to enable a computer to connect to one another and to exchange information known as PROTOCOL.
- TCP/IP is the only protocol used to send data all around the Internet.
- TCP/IP is made up of two components—TCP and IP.
TCP (Transmission Control Protocol): TCP breaks up the data to be sent into packets. It guarantees that any data sent to the destination computer reaches it.
IP (Internet Protocol): IP is a set of conventions used for routing packets from one host to another. It is responsible for routing the packets to a desired destination IP address.
Define different types of Verbal Communication. (U. P. 2008)
Verbal Communication. When any data or information is transferred verbally from one place to another, it is known as verbal communication, such as the communication between two persons on the telephone.
Different types of Verbal Communications are:
- Telephone: With the help of telephone, we can converse with others from a distance. The communication is verbal in this case and the medium is wire.
- Intercom: It is just like telephone technology, but it is limited to a building or campus for the purpose of conversation between the two.
- Mobile: It is the modem technology of the telephone system. In this, we can also converse with each other, but the medium in this is magnetic wave through the air.
- Chatting through Computer: In this technology, we can exchange our views and thoughts verbally by using a microphone. The medium in this technology is the telephone.
Explain the ISO reference model. (U. P. 2016, 19)
An interconnected protocol for the computer to computer communication as recommended by the International Standards Organisation (ISO) is gaining wide acceptance. It is an approach based on defining a number of distinct layers each addressing itself to one aspect of linking. This is known as the ISO model for Open System Interconnection. It is a seven-layer architecture and defines a separate set of protocols for each layer.
Define satellite Communication.
- Line of sight required between satellite and earth stations.
- 12 to 24 transponders per satellite. These transponders receive, amplify, change frequency and transmit.
- Geosynchronous orbit (22,300 miles).
- Low security—anyone with satellite dish and right frequency can tune in.
- Ease of adding stations.
- Data rates of up to 50 Mbps.
- Microwave signal at 6 GHz is beamed to it from a transmitter on the earth.
It is amplified and retransmitted to the earth at 4 GHz by a system called a transponder mounted on the satellite to avoid interference.
Explain Data Communication. (U. P. 2017)
Communication refers to the electronic transmission of any type of electronic information encompasses telephone communication, the transmission of television signals, data communication of all forms, electronic mail, facsimile transmission, and so on.
Data communication is the movement of encoded information from one point to another by means of an electrical or optical transmission system, such systems often are called data communication networks.
Computer and Communication Very Short Answer Type Questions (2 Marks)
Give names of various type of communication media. (U. P. 2014)
Communication media are of two types:
- Guided or Wired media:
- Twisted pair cable
- Coaxial cable
- Optical Fibre Cable.
- Unguided or Wireless media:
How many layers are there in the ISO model? (U. P. 2016)
There are seven layers in the ISO model.
Which layer is responsible for file transfer?
The application layer is responsible for file transfer.
Which communication is used to link metropolitan cities?
Microwave communication is used to link metropolitan cities.
Discuss Wireless Communication Media. (U. P. 2014)
In this type of media, wires are not used, means not physical connection.
At how much distance are the repeaters used in microwave transmission?
Repeaters are used at a distance of 30-35 km in microwave transmission.
What is RS-232-C?
RS-232-C is a kind of protocol which is used to link a digital device to the modem.
Explain the full form of E-mail.
The full form of E-mail is Electronic Mail.
Computer and Communication Objective Type Questions (1 Mark)
There are four alternative answers for each part of the questions. Select the correct one and write in your answer book:
Which communication media has a data rate of up to 20 Mbps?
(a) Coaxial cable
(b) Twisted cable
(c) Fibre optic
(b) Twisted cable
Which is not a protocol? (U. P. 2014)
Which is not a physical communication channel?
(a) Twisted pair
(b) Coaxial pair
(c) Fibre optic
In which media, transponders are used? (U. P. 2012, 14)
(c) Fibre optic
(d) Twisted cable.
Transponders are used in which communication media? (U. P. 2014)
(a) Fibre optic
(d) Co-axial cable.
(d) Co-axial cable
Which of the following is not Hardware? (U. P. 2015)
In which transmission medium the data transmits in the form of light waves? (U. P. 2017)
(a) Copper wire
(b) Coaxial Cables
(c) Telephone lines
(d) Optical Fibre Cable.
(b) Coaxial Cables
Which of the following is not an input device? (U. P. 2018)
Which one of the following is an O.S.? (U. P. 2018, 19)
(c) Pen drive
Which of the following is not a hardware device? (U. P. 2018)
What type of communication happens in Computer Communication? (U. P. 2019)
(b) Full duplex
Whose Communication range is high among the following? (U. P. 2019)
(a) Cable Communication
(b) Microwave Communication
(c) Satellite Communication
(d) Radio Communication.
(c) Satellite Communication