COMPUTER NETWOKS TYPES-LAN;MAN;WAN AND ITS AREA

Depending on the coverage area of Network, it is divided in three types.
They are:
a) Local Area Network (LAN)
b) Metropolitan Area Network (MAN)
c) Wide Area Network (WAN)

a) Local Area Network (LAN)
A computer network that is spread in a small local area is known as Local Area Network (LAN). The network of computers within a room, building or campus is Local Area Network. Computers in a LAN are usually connected with cables. So, the data transmission speed is very high in a LAN. Now-a-days, wireless media are used to connect computers on the network. The type of LAN where wireless media are used is called Wireless LAN or WLAN.

b) Metropolitan Area Network (MAN)
A computer network, that is bigger than LAN and smaller than WAN, is Metropolitan Area Network (MAN). The network of computers within a city or in between neighboring cities is MAN. There may be large numbers of LANs in a MAN. The cable television (CATV) of the city is the example of MAN.

c) Wide Area Network (WAN)
The network of computers within a country or continents is known as Wide Area Network (WAN). The WAN links computers of the country with computers of other countries like India, America, Japan, etc. The WAN covers the very large geographical area i.e. the whole world. The WAN can have many MANs and LANs. The Internet is an example of WAN.


INTRANET
An intranet is a private computer network owned by a company or an organization and is accessible only to its employees. It uses internet protocols, network connectivity and telecommunication system to share a part of the organization’s information or operations with its employees. The features of the intranet are:
i. Intranet runs on private networks within a company and among its branch offices.
ii. Intranet is closely related to the Internet.
iii. Intranet serves as a powerful tool for communication within an organization.
iv. Intranet helps the employees to quickly find and view information and applications relevant to their roles and responsibilities within the organization.

COMPUTER NETWORK AND SHARING

INTRODUCTION:

The word ‘Network’ refers to an interconnected system. The network of roads within a country connects different cities of the country. The network of telephones connects telephone system of the country. Many telephones are connected with each other by means of telephone wires in the telephone network. In the same way, we can connect two or more computers of the same place or different places. To connect computers of near by places we use cable other wireless media. Computers of far places can be connected through some media such as telephones lines, radio wave, communication satellite, etc. Such an interconnection of computers is known as Computer Network.

Computer Network refers to the group of computers which are interconnected to each other by means of transmission media like cables or without cables. A computer network may have one or more server computers and client computers. The server computer on the network acts as the storehouse and distributor for the data, information and programs. The server computer also provides facilities of sharing hardware to the computers on the network. A server computer uses network operating software like Window NT Server, Novel Netware Server, UNIX, LINUX etc. The other computers on the networks are workstations. The workstation is also known as Client computers. The workstations use the resources provided by the server computer.

When computers are on the network they can transfer data, information and programs among themselves. Computer network made it possible to book an airplane ticket, reserve the room in hotel, purchase goods and much more. Offices, Organizations, Companies, Universities etc. Keep their computers on the network for the following reasons.
a. To share computer hardware like printer, scanner etc.
b. To share data, information and programs.
c. To send or receive message i.e. to communicate with each other.


ADVANTAGES OF NETWORK
The main purpose of computer network in for data communicate but one can benefit the following advantages from the computer network.

a. Data and information sharing
The main advantage of computer network is sharing data and information. While working in a computer you may need to share data and information with other person. If you are using a stand-alone computer, you have to copy data and information on a portable storage device or take hardcopy output and send it to the required person. This process needs some portable storage devices, papers, a printer and one additional person to carry the potable storage devices or printouts. In a network environment, data and information stored on computers can be shared with each other. You don’t need portable storage devices, papers, printers and additional person to carry portable storage devices or printouts.

b. Hardware Sharing
Computers on a network can their hardware resources. Network is impractical for each computer of an office, or an organization to have computer hardware like laser printer, scanner, fax machine, etc. A printer connected with one of the computers on the network can be used by any other computers on the network. Similarly other resources which can be shared on a network are scanners, hard disk, modem, CD-drives and fax machine.

c. Software Sharing
In a network environment, software resources can be shared effectively among the computer on the network. In stand-along environment, the software to be used must be present on each computer. It is time consuming to install and configure the software individually on each computer. In a network environment, the software can be centrally installed and configured on a server and be used on other computers on the network. A computer on the network can legally share the copies of software with other computers on the network.

d. Communication facilities
Network users can send or receive instant message to each other at vary fast speed.

e. Security
Only an authorized user can access the resources of network. Normally, there are at least two servers (Primary Domain and Secondary Domain) on a network. These server computers centrally stored data, information, files and software. By mistakes or accidentally if data and files are deleted then they can be recovered easily from one of them.

f. Cost Factor
The sharing of hardware and software reduce economic burden. Messages can be sent and received at economic price.

MULTIMEDIA EXPRESS

The world ‘MULTIMEDIA’ is made up of two words: ‘Multi’ and ‘Media’. The word ‘multi’ refers to more than one and the word ‘media’ refers to the way through which one can express information. There are many different media to communicate information. The different media used to communicate information are text, audio, video, picture and animation. The information can be presented more effectively and understandable way by using more than one medium.

Multimedia is technology of presenting information in more attractively, interesting, interactive and understandable manner, different media like text, pictures, videos, sounds and animations are used in a multimedia. So, multimedia is the communication of more than on medium which present information in more interesting, interactive and understandable ways. Many software companies, institutes, training, centers etc. have developed interactive multimedia. It is an interactive multimedia, there is provision of reading, learning, writing saving information of a subject at the user desired time as well as the user can text him/her knowledge on a subject within the specified time frame. Since the compact disk is only of the chipset, portable and high storage disk. So, multimedia are available in compact disk are these CDs are called Multimedia CD. Encyclopedia, Tutorial CDs, TOFEL CD, etc are example of interactive multimedia compact discs.

To use the multimedia application, a computer should have all the necessary hardware and software which can handle more than one media. A computer which can handle or present more than one medium (text, audio. Images, video and animation) simultaneously is known as multimedia computer or multimedia system. The multimedia computer should have sound card, speaker, microphone, high resolution, monitor high speed microprocessor, large RAM capacity, high capacity hard disk and CD or DVD drive. Except these to capture movies or pictures from external devices like TV, VCR or camcorder, it should have video player, Microsoft power point, Xing player, power DVD, macromedia Flash, photo shop, 3D Max, Maya etc., to handle those media.


COMPONENT OF MULTIMEDIA
To convey information effectively all the components of multimedia must be used properly. The components of multimedia are text, audio, Images, video and animation.

a. Text
Text is the primary component of multimedia. Most of the information is conveyed through the text. The used of different styles, fronts and colors can be used to emphasize the texts. Text can be combined with the other media in the powerful and meaningful ways to present information.

b. Pictures
A computer can digitize and handles picture and graphic. Images created in different applications can be stored in a computer as TIF (Tagged Images File), BMP (Bitmap), GIF (Graphic Interchange Format), WMF (Windows metafile Format), JPEG (Join Photographic Expect Groups) file formats. Pictures or graphics play a key role in multimedia. Presenting information using text and images media give concept than presenting information using only using text medium. Pictures help in explaining concepts through illustrations and charts. The information presented by using texts and pictures media retain for a long times in the memory than that of the text medium.

c. Sound
Sound is very important aspect of multimedia. Computers are digital technology have changed the quality of music considerably. Digital music is used to produce special music and sound effects, which are used not only to accompany animation but also to increase interactivity with the user.

d. Animation
Animation refers to simulation of movements created by displaying a serial of pictures one after the other. Animation can explain a procedure more accurately than that of movie. Nowadays animations are mostly used to explain how did anything happen. For example the germination of plant can explained more clearly through animation. Cartoons such as Pokemon, Tom and Jerry, Donald duck, Power Puff Girls example of computer animation.

e. Video
Video refers to pictures in motion. Video is the excellent way to convey messages to the user in a limited time. Video also increases the retention of information for a long time in the memory of people.

MULTIMEDIA SOFTWARE
The following table lists the different multimedia software and their uses in various application fields.
Name of Multimedia Software-------------------------------Application Fields
1. Adobe PhotoShop----------------------------------------Creating Graphics.
2. Macromedia Flash, Animator----------------------------Creating 2D animations.
3. 3D Studio Max----------------------------------------------Creating 3D animations.
4. Microsoft PowerPoint----------------------------------------Creating Presentations

ADVANTAGES OF MULTIMEDIA
These are some advantages of multimedia.
1. One can present ideas, information to others in effective ways.
2. Using multimedia technology, a subject can be taught in interesting and effective ways in the classroom.
3. Students can learn, read and test his/her knowledge using multimedia technology.
4. A country can be used multimedia technology to uplift tourism sector of a country.
5. Games and movies are made more realistic using multimedia technology.
6. Electronic advertising can be made more interesting.
7. In video songs, one can put animations.

APPLICATION OF MULTIMEDIA TECHNOLOGY

Multimedia technology is used in games, learning software, reference materials like encyclopedia, movies, web pages, advertisement, virtual reality and some others fields.

a. Multimedia in Education and Training

The use of multimedia in education is increasing rapidly. Multimedia in education’s power to present information in creative ways has led to the creation of rich learning environments. Multimedia enables students to grasp the concept easily and quickly. In addition, students retain the information for longer time. Educational Multimedia CD i.e. CAL (Computer Assisted Learning) helps students to learn different subjects. The use of sound, pictures and video enables the students to observe a real world situation which is just not possible with the more conventional methods of instruction. For examples, using Flight Stimulators aircraft pilots are trained to control aircrafts.

b. Multimedia in Business

Nowadays multimedia is used in almost every aspect of business. To convey and present information about business or products multimedia is used in business. Some of the uses are given below.

- Interactive training: Organizations use multimedia to provide interactive training programs to their employees through a network or CDs.

- Video Conferencing: Video Conferencing enables virtual face-to-face communication among people sitting at different locations. All locations simultaneously receive the audio, video, or data that the location transmits.

c. Multimedia in Advertising

With the use of multimedia advertisers find new and creative ways of advertising and marketing products. Everything that the human mind imagination can be presented realistically through the use of multimedia. This means that for advertisers who use this technology, there is no limit to the number of ways in which they can advertise a given product.

d. Multimedia in Games and Movies

Multimedia is used in video games. There are many interesting video games like Snake and Ladder, Prince of Persia, PC-Man etc., where multimedia technology is used.

In many movies, special effects are kept with the help of multimedia technology which is not possible without it. For example, Terminator, Titanic, Start Wars, Jurassic Park, King Kong, Godzilla etc. are some English movies where special effects are used. Similarly, in video and audio songs multimedia technology is used to put some special effects.

e. Multimedia in Internet

Multimedia technology is widely used in Internet. Information in websites are presented beautifully using multimedia technology.

VIRTUAL REALITY

Virtual Reality is an artificial environment created with the computer hardware and software and presented to the user in such a way that it appears real. To enter virtual reality, a user puts on special gloves, earphones and goggles, all of which receive inputs from the computer system. Today, virtual reality is primarily used in the entertainment industry but it is going to be very useful tool for simulation purposes and remote control applications. However, virtual reality systems require extremely expensive hardware and software.

MICROSOFT WINDOWS OF GRAPHICAL USER INTERFACE (GUI)

Microsoft window is an operation system. An operation system is a program that tells the computer how to work. Operation system makes the hardware of the computer functions. Operation system manages the input, output, memory, storage and retrieval of data.

GUI based operation system

Windows operation system is user friendly i.e. Windows operation is easy for anyone to use windows operation system. We do not have to remember the commands. We communicate with the computer using symbols and graphic.

GUI stands for Graphic User Interface. A GUI based operation system is a program. GUI uses icons, menus, dialog boxes and windows to display information on screen. Windows in such GUI based operation system. It allows the user to select and click items with the help of the mouse.

In Windows, different programs are represented graphically be icons, so we can easily recognize programs. It is very easy to use windows because of this. That is why, windows is called Graphical User Interface (GUI). This feature of windows made it very popular and user friendly.
MS-Windows 98, MS-Windows 2000, Windows XP etc. are some GUI based operation system.

Starting Windows …………
1) Connect the main power chord from the back of the CPU to the main plug (on the wall).
2) Switch on the main power socket and then the computer. Wait for sometime until Windows fully gets loaded and shows the windows desktop on the screen (as shows below). Now, you are ready to use windows.

The Desktop
What do we usually have on our desk? Papers, pens, pencils, books, etc. Similarly, desktop in Windows is what we see on the screen, when windows get loaded on the computer. Desktop is the screen with icons and a taskbar at the bottom with a start button on the left.

Icons
Icons are small pictures on the desktop that represent various programs or programs files.

Taskbar
The bar which is located at the bottom of the windows desktop is called as the taskbar. It shows the names of the programs items that we have minimized. The programs which we are not working currently can be minimized by clicking the minimized button ( _ ) through we can continue working with the current application.
The taskbar also contains the start button. We can click on the start button and get other menus from which we can run different programs.

PRINCIPLE OF KEYS OF THE KEYBAORD

The Keys can be classified as given below:

1. Alphabetic Keys:
All the letters or alphabets from A-Z or a-z are the alphabetic keys. Alphabetic keys are used to type words, sentences, paragraphs etc.
Example: Q E R T Y U I O P
A S D F G H J K L
Z X C V B N M

2. Numeric Keys:
Numeric Keys are those, on which numbers are printed. Numeric Keys are used to type the numeric information like age, phone number, postal code etc.
Example: 1 2 3 4 5 6 7 8 9 0

3. Cursor Movement Keys:
Cursor is a flashing point on the screen that indicates the location, where the next character will appear. Cursor movement keys help the cursor to be moved to the position where you want to type the information.
a. Up arrow (↑): moves the cursor one line up.
b. Down arrow (↓): moves the cursor one line down.
c. Right arrow (→): moves the cursor towards the right.
d. Left arrow (←): moves the cursor towards the left.

4. Symbolic Keys:
Symbolic keys are used to give symbolic information to the computer and carry out different functions. Symbolic keys appear above the numbers 0, 1, 2 …………The Shift key is used to type them.
Example: ! @ # $ % ^ & * ( )

5. Special keys:
Three are different special keys present on the keyboard. Each of them have their own special function.

i. Control keys: Ctrl
Control keys used along with some other keys to carry out different functions according to different software used. E.g. Ctrl + X will cut the selected text in MS-Word

ii. Alternate key: Alt
The Alt key is also used along with some other keys to carry out different functions. E.g. if you just press the Alt key, menu will be activated in any menu based program.

iii. Delete key: Del
Delete key is used to delete one character right to the cursor position. E.g. if the cursor is in between the alphabet P and O of the word POT, pressing the delete key will erase the alphabet O

iv. Back space key: ← Backspace
The Back space key removes one character to the left of the cursor position. E.g. if the cursor is between the alphabet P and O of the word POT, pressing the backspace key will erase the alphabetic P

v. Enter key: Enter
When the enter key is pressed, the information typed is sent to the computer’s memory for processing. It also indicates the end of the program.
Ctrl + Alt + Del
These three keys are pressed together to restart the computer.

vi. Shift key: Shift
The Shift key is used along with the other alphabetic keys to produce capital letters (when caps lock is off). It is also used to produce the special keys (upper character of the key).E.g.
Shift + m = M
Shift + 6 = ^

vii. Num lock key: Num Lock
If the Num lock is OFF, the numeric keys on the numeric keypad (present on the right hand side of the keyboard) is used for cursor movement. But if it is ON, it is used to type the numbers of the numeric keypad. Num lock can be toggled i.e. it can be made ON or OFF by pressing it alternatively.

viii. Caps lock key: Caps Lock
This is also a toggle key. That is, the caps lock key when turned ON (light can be seen when ON) types the letter in capital letters. When it is OFF, letters are typed in small letters.

ix. Insert key: Insert
Insert is used to type a character in between the characters they are already typed. When it is OFF (insert OFF), the text matter on the right hand side will automatically Shift towards the right and adjust the new character typed.

Home
Home key moves the cursor to the beginning of the line.

End
End key moves the cursor to the end of the line.

Esc
The Escape key is used to cancel the command.

Page up
Page up key moves one page up i.e. moves the current page upward and the lower page appears on the screen.

Page down
Page down key moves the current page down by one page and thus the upper page appears on the screen.

Print screen
Print key prints the text appearing on the screen.

Pause
The scrolling of the screen is paused, when this key is pressed.

Tab
Tab key helps the cursor jump at a definite position in the line.

6. Functional keys:
They are used to issue or give common commands. They lie at the top row of the keyboard.
Example: F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12

WORKING IN DOS ENVIRONMENT

Disk Operating System in a Command Line Interface (CLI) based operating system introduced by Microsoft Cooperation in 1981. Disk Operating System was developed for IMB PC.
Nowadays Disk Operating System is not used in computer. Disk Operating System has been replaced by GUI based operating system. But still GUI based operating system provides facilities of MS-DOS commands. There are some programs they are still based on CLI.

To get the DOS environment i.e. Command prompt in the computer having operating system like Windows 98 or Windows XP, follows these steps.

• Click on start menu.
• Point to all programs, Accessories.
• Click command prompt option.

You can also get DOS prompt (Command Prompt) where you follow these steps.

• Click on start button.
• Click on Run command. It open Run dialog box.
• Type command in the text box if OS is Window 98.

Or,

• Type cmd in the text box if OS is Windows XP.

In Dos environment, a folder is known as a Directory.

MS-DOS Commands
There are many DOS commands but you will learn very few DOS commands. Every DOS command has its syntax that tells how to write a command in proper order.

1. DIR Command
This command lists all the files and sub-directories of a drive or a directory.
Syntax:
DIR [Drive:][path][filename][/P][/S][/A][:] [Attributes][/O]
Where,
[drive:][path][filename] -------- Specifies drive, directory and files to list.
/P ----------------------------------- Pauses after the each screen full display.
/S ----------------------------------- Displays contents of subdirectories.
/O ----------------------------------- List files in sorted order.
The sorted orders are:
D ------------------------------------ by date and time
E ------------------------------------ by extension
N ------------------------------------ by name
S ------------------------------------ by file size
/A ----------------------------------- Display files with specified attributes.
The attributes are:
D ----------------------------------- Directories
R ----------------------------------- Read only files
H ----------------------------------- Hidden files
S ----------------------------------- System files

Examples:
C:\> DIR
This command lists all the files and directories in the drive C:.

C:\> DIR C:\Documents and Settings
This command lists all the files and directories of Documents and Setting directory.

C:\> DIR QBASIC
This command lists all the files and directories of QBASIC directory.

C:\> DIR/P
This command lists files of drive C pausing after a screenful display.

C:\> WINDOWS>DIR SYSTM\*.INI
Displays files having .INI extension of SYSTEM subdirectory of WINDOWS directory of drive C:

Note:
- A root directory is the initial directory or main directory. The disk drive is indicated as C: or D: which is called root directory.
- Asterisk (*) and question mark (?) are known as wild cards in MS-DOS.
- The asterisk (*) represents one or more characters in a file whereas question mark represents only one character in a file.


2. CD or CHDIR command
This command changes directory from one directory to another.
Syntax:
CD [drive:]
Or
CD … or CD\
Where,
Drive: refers to disk drive like C:, D: or A:
Path: refers to directory.

Examples:
C:\>Documents and Settings\Ratna> CD\
The prompt change to C:\>. It directly changes from any directory to the root directory.

C:\> Nepal>CD….
The prompt changes to C:\>. This indicates that now the working directory is drive C:.

C:\> CD QBASIC
Changes directory to QBASIC of drive C: i.e. C:\QBASIC>. Now QBASIC is the working directory.


3. CLS command
This command clear the screen.
Syntax: CLS


4. MD command
MD command is used to create a directory in a disk.
Syntax: MD [drive:]path

Examples:
C:\> MD Nepal
Creates a directory name Nepal in drive C.

C:\> QBASIC>MD Class
Creates a directory name Class in QBASIC directory of drive C.

C:\> Nepal>MD Koshi
Create a Koshi directory in Nepal directory of drive C.


5. RD command
This command removes an empty directory from a disk.
Syntax: RD[drive:]

Examples:
C:\> RD GAME
Deletes a directory name GAME from the root directory of drive C.

C:\> RD C:\Work\Homework
Deletes a directory Homework from Work directory of drive C.


6. DEL or ERASE command
DEL or ERASE command deletes a file or group of files.
Syntax:
DEL [drive:][path]filename

Examples:
C:\DEL C:\Windows\Temp*.*
Deletes all the files of Temp subdirectory of Windows directory of drive C.

C:\QBASIC>DEL A*.BAS
Deletes all files whose name start with ‘A’ and have extension. BAS from QBASIC directory of drive C.


7. REN or RENAME command
This command renames a file.
Syntax:
REN [drive:][path] old_filename New_filename

Examples:
C:\>REN Nepal.TXT NewNepal.TXT
Renames Nepal.TXT of drive C as NewNepal.TXT.

C:\>REN QBASIC\DIGITSUM.BAS NUMSUM.BAS
Renames DIGITUM.BAS of QBASIC of drive C as NUMSUM.BAS


8. TYPE command
This command displays the contents of a file.
Syntax:
TYPE[drive:] [path]filename

Examples:
C:\>TYPE BABU.txt
Displays the contents of BABU.txt file of drive C.

C:\>QBASIC>TYPE NUMSUM.BAS
Displays the contents of NUMSUM.BAS file of QBASIC directory of drive C.


9. COPY command
This command creates a duplicate of the original files.
Syntax:
COPY[Source-drive:][path]filename [Target_drive:][path]

Examples:
C:\>COPY NAYADESH.TXT D:\
Copies NAYADESH.TXT file of drive C to drive D.

C:\>COPY C:\QBASIC\*.BAS D:\
Copies all files having .BAS extension of QBASIC directory of drive C to drive D.


10. EXIT command
The EXIT command is used to exit from MS-DOS and return to Windows XP.
Syntax: EXIT

Examples:
C:\>EXIT
This exits from DOS environment.

OPEN SOURCE SOFTWARE OR FREE SOFTWARE

INTRODUCTION

Open Source Software (OSS), also called Free Software (FS), are programs whose General Public Licenses (GPLs) give users the freedom to run the program for any purpose, to study and modify the program, and to redistribute copies of either the original or modified program (without having to pay royalties to previous developers). Some OSS/FS software are good and some are technically poor. Good software may also not fit as your specific needs. OSS/FS users have control over the software. So, they can modify and maintain OSS as their needs.

Since freeware are also freeware for the users, it is not OSS/FS. A freeware is proprietary software that is available to the computer users without any cost and does not provide the rights in examine, modify, and redistribute the program’s sources code. Ni the case of proprietary (close source) software, the software company completed controls the product. The company hides security holes and fundamental flaws from the users. The users are not allowed to modify the programs to suit their own needs. This type of monopoly is removed in open source software, where anybody can or change the software for their own needs.

Advantages of Open Sources of Software
The advantages of open source software are listed below.

1. One of the major advantages of open source software is the availability of the source code and the right to modify it. open source software enables the unlimited turning and improvement of a software product. Sources code availability also makes it much easier to isolate bugs, and (for a programmer) to fix them.
2. The users have the right to redistribute modifications and improvements to the code.
3. The users have the right to use the software in any way.
4. There is no single entity on which the future of the software depends. In the case of proprietary software, it the software manufacturer closes or decides to discontinue development of the product, no one has right to take the program and continue development on it. Open sources software effectively protects against this, because if the group or company that originated the codes decides to stop development, it is always possible to fund another software group to continue the maintenance and improvement, without neither legal nor practical limitations.

Disadvantages of Open Source of Software

1. Only the programmers can modify the source codes of open source software as their needs.
2. Since there is no company or groups responsible for the development for the open source software. So, there is no guarantee that development will happen.
3. There may be significant problems connected to intellectual property.