FINAL TEST TRYOUT

FINAL TEST TRYOUT GRADE 7

FINAL TEST TRYOUT GRADE 8

FINAL TEST TRYOUT GRADE 9

UNIT 4

GLOBAL NETWORK

4.1       World Web Wide

Definitions

The World Wide Web ("WWW" or simply the "Web") is a global information medium which users can read and write via computers connected to the Internet. The term is often mistakenly used as a synonym for the Internet itself, but the Web is a service that operates over the Internet, just as e-mail also does. The history of the Internet dates back significantly further than that of the World Wide Web.

History of the Web

Sir Tim Berners-Lee is a British computer scientist. He was born in London, and his parents were early computer scientists, working on one of the earliest computers.

Growing up, Sir Tim was interested in trains and had a model railway in his bedroom. He recalls:

“I made some electronic gadgets to control the trains. Then I ended up getting more interested in electronics than trains. Later on, when I was in college I made a computer out of an old television set.”

After graduating from Oxford University, Berners-Lee became a software engineer at CERN, the large particle physics laboratory near Geneva, Switzerland. Scientists come from all over the world to use its accelerators, but Sir Tim noticed that they were having difficulty sharing information.

“In those days, there was different information on different computers, but you had to log on to different computers to get at it. Also, sometimes you had to learn a different program on each computer. Often it was just easier to go and ask people when they were having coffee…”, Tim says.

Tim thought he saw a way to solve this problem – one that he could see could also have much broader applications. Already, millions of computers were being connected together through the fast-developing internet and Berners-Lee realised they could share information by exploiting an emerging technology called hypertext.

In March 1989, Tim laid out his vision for what would become the web in a document called “Information Management: A Proposal”. Believe it or not, Tim’s initial proposal was not immediately accepted. In fact, his boss at the time, Mike Sendall, noted the words “Vague but exciting” on the cover. The web was never an official CERN project, but Mike managed to give Tim time to work on it in September 1990. He began work using a NeXT computer, one of Steve Jobs’ early products.

By October of 1990, Tim had written the three fundamental technologies that remain the foundation of today’s web (and which you may have seen appear on parts of your web browser):

• HTML: HyperText Markup Language. The markup (formatting) language for the web.
• URI: Uniform Resource Identifier. A kind of “address” that is unique and used to identify to each resource on the web. It is also commonly called a URL.
• HTTP: Hypertext Transfer Protocol. Allows for the retrieval of linked resources from across the web.

4.2       The Internet is Global

The Internet is the global system of interconnected computer networks that use the Internet protocol suite (TCP/IP) to link billions of devices worldwide.

This statistic gives information on the total number of worldwide internet users from 2005 to 2015. As of the most recent reported period, the number of internet users worldwide was 3.17 billion, up from 2.94 billion in the previous year.

September 2, 1969: First time two computers communicated with each other. Oct 29, 1969: Message sent from computer to computer in different locations. Jan 1, 1983: ARPANET adopted the standard TCP/IP protocol. March 1989: Tim Berners-Lee invented the World Wide Web.

global network is any communication network which spans the entire Earth. The term, as used in this article refers in a more restricted way to bidirectional communication networks, and to technology-based networks.

4.3       Searching for Information on the Internet

How to find information on the Internet

Most information is found on the Internet by utilizing search engines. A search engine is a web service that uses web robots to query millions of pages on the Internet and creates an index of those web pages. Internet users can then use these services to find information on the Internet. When searching for information on the Internet, keep the below things in mind.

Surround searches in quotes

If you are searching for multiple common words, such as computer and help, it is a good idea to place quotes around the full search to get better results. For example, type "computer help" as your search criteria. This trick can also be used in parts of your search query. For example, Microsoft "computer help" would search for anything containing 'Microsoft' and that also has "computer help" together. Finally, you can also do multiple words surrounded in quotes. For example, "Microsoft Windows" and "computer help" would refine your results even more.

Be aware of stop words

Many search engines will strip out common words they refer to as stop words for each search that is performed. For example, instead of searching for why does my computer not boot, the search engine would search for computer and boot. To help prevent these stop words from being stripped out, surround the search with quotes.

Tip: If stop words are not important, don't enter them into your search.

Familiarize yourself with Booleans

Many search engines allow Booleans, which can help filter out bad results. Although common Booleans include "and", "or", and "not", most search engines have replaced these keywords with symbols. For example, to find computer help without results containing Linux, you would type computer help -linux. The "-linux" tells the search engine to exclude any results containing the word Linux.

Know what features are available

Many search engines allow for additional syntax to help limit your search strings. For example, Google enables users to search for links to a particular page by typing "link:" and other keywords at the beginning of the search query. For example, to see who is linked to Computer Hope, you'd type: link:http://www.computerhope.com.

Unit 3      

 Internet Protocol: TCP/IP

33.1   Packet of data

Definition - What does Data Packet mean?

A data packet is a unit of data made into a single package that travels along a given network path. Data packets are used in Internet Protocol (IP) transmissions for data that navigates the Web, and in other kinds of networks.

Structure of a Data Packet

The structure of a packet depends on the type of packet it is and on the protocol. Read further below on packets and protocols. Normally, a packet has a header and a payload.

The header keeps overhead information about the packet, the service, and other transmission-related data. For example, data transfer over the Internet requires breaking down the data into IP packets, which is defined in IP (Internet Protocol), and an IP packet includes:

• The source IP address, which is the IP address of the machine sending the data. 
• The destination IP address, which is the machine or device to which the data is sent.
• The sequence number of the packets, a number that puts the packets in order such that they are reassembled in a way to get the original data back exactly as it was prior to transmission. 
• The type of service
• Flags
• And some other technical data
• The payload, which represents the bulk of the packet (all the above is considered as overhead), and is actually the data being carried. 

33.2   Circuit switching vs. packet switching

Circuit Switching

In circuit switching network dedicated channel has to be established before the call is made between users. The channel is reserved between the users till the connection is active. For half duplex communication, one channel is allocated and for full duplex communication, two channels are allocated. It is mainly used for voice communication requiring real time services without any much delay. 

 
As shown in the figure 1, if user-A wants to use the network; it need to first ask for the request to obtain the one and then user-A can communicate with user-C. During the connection phase if user-B tries to call/communicate with user-D or any other user it will get busy signal from the network.

Packet Switching

In packet switching network unlike CS network, it is not required to establish the connection initially. The connection/channel is available to use by many users. But when capacity or number of users increases then it will lead to congestion in the network. Packet switched networks are mainly used for data and voice applications requiring non-real time scenarios. 
 
As shown in the figure 2, if user-A wants to send data/information to user-C and if user-B wants to send data to user-D, it is simultaneously possible. Here information is padded with header which contains addresses of source and destination. This header is sniffed by intermediate switching nodes to determine their route and destination.

In packet switching, station breaks long message into packets. Packets are sent one at a time to the network. Packets are handled in two ways, viz. datagram and virtual circuit.

In virtual circuit, preplanned route is established before any packets are transmitted. The handshake is established using call request and call accept messages. Here each packet contains virtual circuit identifier(VCI) instead of the destination address. In this type, routing decisions for each packet are not needed.

Unit 3

Parts of a Computer

 

3   3.1   The Basic Operations of Computer

5 Basic Operations of a Computer System

1. Processing
2. Outputting
3. Storing
4. Controlling

Input Unit

Inputting is a basic operation of a computer system. This is the act of feeding in the data and instruction to the computer (by computer here it means the processing unit).

A computer system consists of different functional units and Input Unit does the operation of Inputting. By inputting you should understand that it is to send data and/or instruction to computer in required format.

Information and programs are entered into the computer through Input devices such as the keyboard, disks, or through other computers via network connections or modems connected to the Internet. The input device also retrieves information off disks.

The devices that helps you to input data and instructions are known as Input Devices. Keyboard, Mouse, Light Pen, JoyStick, Scanners, Microphone etc are some examples of input unit devices.

Processing Unit

The task of performing calculations and comparisons are known as processing. The unit in Computer System that is responsible for processing is ALU (Arithmetic and Logical Unit).

ALU is the place where actual execution of the instructions takes place during the processing operations. All calculations & comparisons are made in the ALU. The data and instructions stored in the primary storage are transferred to it as when required. ALU may produce Intermediate results and store it in the memory which are also transferred back to the ALU for the final processing. After completion of processing the final results are send to storage units from ALU.

Output Unit

This unit takes care of receiving processed information from processing unit and present it to the user in suitable form. A computer produces results in binary form and output unit does decoding to make it usable to the users.

The devices that can output information from computer are known as output unit devices. Monitors, Speakers, Projectors are soft output devices whereas printers, plotters produces hard copy output.

Softcopy output is something that is temporary or is available only as long as output device is turned on. Contrary to these are hard copy output which are permanent. The printout in a paper is not lost because printer is turned off!

Storage Unit

Before actual processing start, data & instructions entered to the computer must be stored somewhere inside the computer. Similarly, results produced by the computer are required to be stored before it is passed to the output unit. The intermediate result produced by the computer must also be stored for further processing. Thus the importance of storage Unit in a computer system is vital.

Based on whether storage device is inside the main machine or not, it can be internal internal or external storage. Similarly, looking at whether the storage device works close with CPU or works as backup media, they can be primary storage or secondary storage. Primary storage are also called primary memory. Secondary storage are known with other names such as backup storage or secondary memory.

For the storage purpose, a computer system may have different devices such as registers, cache, RAM/ROM, flash, magnetic disks, optical disks and so on.

Control Unit

ALU dose not know what should be done with the data likewise, output unit dose not know when the result should be displayed. By selecting, interning and seeing to the execution of the program the CU is able to maintain order and direct the operations of the entire system. CU doesn’t perform any actual processing on data yet it is known as a central nervous system for the comforts of the computer.