WEEK 4: DATA 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 the letter, if the PC is connected to all the client's PC 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 programs 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.

Type  Of Signal             

• Data come on a variety at styles : text,pic, etc....

   

Analogue Signal

• Human voice
• It is formed by continuously varying voltage levels that create wave that can be grasped by an analogue transmitter like microphone.
• Represent by thier character the wave.
• Frequency-number of complete wave circle.[Hertz(Hz)] 
• Amplitude-wave height measured by voltz(v)/decibel(dB).  
• Analogue signal is transmitted

      
             

Digital Signal

• Digital signals are signals that are represented by binary numbers, "1" or "0". The 1 and 0 values can correspond to different discrete voltage values, and any signal that doesnt quite fit into the scheme just gets rounded off. Digital signals are sampled, quantized & encoded version of continuous time signals which they represent. In addition, some techniques also make the signal undergo encryption to make the system more tolerent to the channel.

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WEEK 3 : WEB SEARCHING

Web broswer?

• Software application that enables a user to display and interact with text, image, and other information typically located an a web page at a website on the World Wide Web or local area network.
• Software that display web page.
• A web browser can also be defined as an application software or program designed to enable users to access, retrieve and view documents and other resources on the Internet.
• Although browsers are primarily intended to access the World Wide Web, they can also be used to access information provided by web servers in private networks or files in file systems. The major web browsers are Firefox, Google Chrome, Internet Explorer, Opera, and Safari.

 Directories

• A web directory or link directory is a directory on the World Wide Web. It specializes in linking to other web sites and categorizing those links.
• A web directory is not a search engine and does not display lists of web pages based on keywords; instead, it lists web sites by category and subcategory. Most web directory entries are also not found by web crawlers but by humans.
• The categorization is usually based on the whole web site rather than one page or a set of keywords, and sites are often limited to inclusion in only a few categories. Web directories often allow site owners to submit their site for inclusion, and have editors review submissions for fitness.

MetaSearch Engine

A metasearch engine is a search tool that sends user requests to several other search engines and/or databases and aggregates the results into a single list or displays them according to their source. Metasearch engines operate on the premise that the Web is too large for any one search engine to index it all and that more comprehensive search results can be obtained by combining the results from several search engines. This also may save the user from having to use multiple search engines separately.

Clear History

Clear History is free and powerfull windows desktop application to clean search history from your computer. It is full featured program that greatly surpasses most commercial programs out there.

Multitasking

Multitasking is a method where multiple tasks, also known as processes, share common processing resources such as a CPU. In the case of a computer with a single CPU, only one task is said to be running at any point in time, meaning that the CPU is actively executing instructions for that task. Multitasking solves the problem by scheduling which task may be the one running at any given time, and when another waiting task gets a turn. The act of reassigning a CPU from one task to another one is called a context switch. When context switches occur frequently enough the illusion of parallelism is achieved. Even on computers with more than one CPU (called multiprocessor machines), multitasking allows many more tasks to be run than there are CPUs.

Plug-in

In computing, a plug-in (or plugin) is a set of software components that adds specific abilities to a larger software application. If supported, plug-ins enable customizing the functionality of an application. For example, plug-ins are commonly used in web browsers to play video, scan for viruses, and display new file types. Well-known plug-ins examples include Adobe Flash Player, QuickTime, and Microsoft Silverlight. 

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TELECOMMUNICATION & NETWORKING ?

A telecommunications network is a collection of terminals, links and nodes which connect to enable telecommunication between users of the terminals. Networks may use circuit switching or message switching. Each terminal in the network must have a unique address so messages or connections can be routed to the correct recipients. The collection of addresses in the network is called the address space.

The links connect the nodes together and are themselves built upon an underlying transmission network which physically pushes the message across the link.

Examples of telecommunications networks are:

• computer networks
• the Internet
• the telephone network
• the global Telex network
• the aeronautical ACARS network

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