computer networking.

 

 INTRODUCTION TO COMPUTER NETWORKS

 

 

DATA COMMUNICATION  :-

when we communicate , we are  sharing  information . The sharing can be local or remote . between individuals, local communication usally oocurs face to face, while remote communication takes place over distance.

components :- 

A data  communication system has five components.

1. message :-

The message is the information (data) to be communicated . popular forms of information include text , number , pictures , audio and video. 

2. Sender :-  

Its a device which sends the data message. It can be a computer ,workstation , telephone handset , video camera and so on.

3. Receiver :-

Its a device that receives the message .

4. Transmission medium :- 

The transmission medium is the physical path by which a message travels fro sender to  receiver . Some examples of transmission media include twisted pair wire , coaxial cable , fibre-optic cable an d radio waves.

5. Protocol:- 

A protcol is a set of rules that govern data communications. It represents an agreement between  the comunicating devices . Without a protocol , two devices may be connected but not communicating just as a person speaking french cannot be understood by a person who speaks only japanese.

 Data representation :-

    Information can be in the form of text , numbers , images, audio, and video.

1. Text:- 

 Text symbols are represented with a sequence of bits 0 and 1. Each sequence is called a code and the process is called coding.Two coding standards are 

• Unicode

• ASCII

• Unicode:- 

unicode is an international coding standard where each letter , digit or symbol is represented with the unique sequence of 32 0s and 1s . so this code can define 232 characters . It can be used in different languages.

Notation :  U-XXXXXXXX

Where X= hexadecimal number and ranges from 0 to F.

• ASCII  :-

American standard code for information interchange is a coding standard where each letter, number or symobls represented with  unique sequence of 7 0s and 1s . so  this code can define 27 (128)  character . It is    used for english language only .

ASCII ( Basic Latin ) is subset of unicode and occupies first 7 bits of unicode for 128 code and is represented in hexadecimal form as :

00000000-0000007F

     2 . Number :-

Number are also represented with a sequence of 0 and 1. ASCII is not used for number representation . Instead , the   following numbering system is used in order to simplify  the mathematical operations :

• Base 10 (decimal)
• Base 2 (binary )
• Base 8( octal)
  
• Base 16 ( hexadecimal)
• Base 256 (IP address)

 Note :-    Number = 789456  

Symbol  =    7   8  9  4  5  6 

Position  = 5  4  3  2  1  0

• Base 10  ( decimal) :-

The base 10 or decimal number system use 10 symbols : 0,1,2 ,3,4,5,6,7,8,9

Weight  = 10 position 

• Base 2 ( binary) :-

The base 2 or binary number system uses two symbols : 0,1 

Weight  = 2position 

• Base 8 ( octal) :-

The base 8 0r octal number system uses 8 symbols : 0,1,2,3,4,5,6,7

Weight  = 8position

• Base 16  ( hexadecimal) :- 

The base 16 or hexadecimal  number system uses 16 symbols :0,1,2,3,4,5,6,7,8,9 A  B  C  D  E  F

Weight   =  16position 

• Base 256 ( IP address) :-

The base 256 number system uses 256 decimal number raging from 0 to 255. It is used to represent ipv4 address where each symbol is separates the position.

For Example ,

IPv4 address : 192.168.1.1

Symbol :   192   168   1    1

position :  3   2    1   0  

weight : 2563  2562  2561  2560

    3.  Images :-

An image is also represented with a sequence of 0 and 1 . A digital image is made up of small units called pixels .Each pixels is assigned a bit pattern whose size depend on the nature of the image.

   4 .  Audio :- 

A  sound which lies within the human frequency range of 20 to 20000 hertz is called  audio . the sound is recorded with microphone  and then digitized  to represent in the form of bit patterns  . Its transmitted form is called an audio signal.

 computer networking :-

A computer network is a system in which multiple computers are connected to each other to share information and resources.

                                 OR

A network is a set of device connected by communication links. A node can be a computer , printer, or any other device capable of sending and/or  receiving data generated by other nodes on the network .

 

 

Characteristics of a Computer Network:-

• Share resources from one computer to another.

• Create files and store them in one computer, access those files from the other computer(s) connected over the network.

• Connect a printer, scanner, or a fax machine to one computer within the network and let other computers of the network use the machines available over the network.

Following is the list of hardware's required to set up a computer network.

• Network Cables
• Distributors
• Routers
• Internal Network Cards
• External Network Cards