introduction to computer

Introduction to Computer Client Server Definition of client server: The term client-server refers to a popular model for computer networking that utilizes client and server devices each designed for specific purposes. The clientserver model can be used on the Internet as well as local area networks (LANs). Examples of client-server systems on the Internet include Web browsers and Web servers, FTP clients and servers, and DNS.

Client and Server Devices: Client/server networking grew in popularity many years ago as personal computers (PCs) became the common alternative to older mainframe computers. Client devices are typically PCs with network software applications installed that request and receive information over the network. Mobile devices as well as desktop computers can both function as clients.

A server device typically stores files and databases including more complex applications like Web sites. Server devices often feature higher-powered central processors, more memory, and larger disk drives than clients.

Peer to peer Peer to peer : Often referred to simply as peer-to-peer, or abbreviated P2P, a type of network in which each workstation has equivalent capabilities and responsibilities. This differs from client/server architectures, in which some computers are dedicated to serving the others. Peer-to-

peer networks are generally simpler, but they usually do not offer the same performance under heavy loads.

peer-to-peer (P2P) network is created when two or more PCs are connected and share resources without going through a separate server computer. A P2P network can be an ad hoc connection —a couple of computers connected via a Universal Serial Bus to transfer files. A P2P network also can be a permanent infrastructure that links a half-dozen computers in a small office over copper wires. Or a P2P network can be a network on a much grander scale in which special protocols and applications set up direct relationships among users over the Internet.

Difference between client server and peer to peer network: Both peer-to-peer and client-server networks connect computers so that resources such as files and applications can be shared. Peer-to-peer networks connect computers so that each computer shares all or part of its resources. Client-server networks have a central computer that holds the data and manages the resources.

1. The Basics o Peer-to-peer networks involve two or more computers pooling individual resources such as disk drives, CD-ROMs and printers. These shared resources are available to every computer in the network. Each computer acts as both the client and the server. Each computer communicates directly with the other computers and can add or remove resources to the network at will.

A client-server network involves multiple clients connecting to a single, central server. Public data and applications are only installed on the server. The client computers connect over the network in order to use the resources. Servers often have private user directories as well as multiple public directories.

2. Advantages o In a peer to peer network, a software application can be installed on a single computer and shared by every computer in the network. They also are cheaper to set up because most desktop operating systems have the software required for the network installed by default.

Client-server networks tend to have faster access speeds because of the large number of clients they are designed to support. The clients are allowed to function as workstations without sharing any resources. It is easier to upgrade software applications and files because they are held on one single computer. Systemwide services can be provided through the server software. Security is enhanced on a client server network because the security is handled by the server. Client-server networks can be extended in order to handle organizational growth. The extent of the growth is only dependent on the hardware available.

3. Disadvantages o Peer-to-peer networks are typically less secure than a client-server network because security is handled by the individual computers, not on the network as a whole. The resources of the computers in the network can become overburdened as they have to support not only the workstation user, but also the requests from network users. It is also difficult to provide systemwide services because the desktop operating system typically used in this type of network is incapable of hosting the service.

Client-server networks have a higher initial setup cost. It is possible to set up a server on a desktop computer, but it is recommended that businesses invest in enterprise-class hardware and software. They also require a greater level of expertise to configure and manage the server hardware and software.

4. Software Installation o Peer-to-peer networks require a software application to be installed on each computer in the network in order for the computer to connect and share resources.

The application is typically installed when the operating system is installed, but needs to be configured to be used. If the network contains multiple operating systems, there may be a third party application that must be installed.

Most of the software required for a client-server network is installed only on the server. Many different types of software including printer, FTP and security software can be installed on a single machine. Client computers only need to have software that enables the computer to connect to the server. Often, the client computers have this software installed by default.

5. Usage o

Due to the security issues and the lack of extensibility, peer-to-peer networks are used in a home network or in an environment where growth is not expected, security is not a concern and there is little or no need for systemwide services.

Client-server networks should be used in environments where growth is expected, security is important and faster access times are required.

Protocols

A protocol is a special set of rules that enable communication between two computers. The commonly used protocols are Transmission Control (TCP/IP), File Transfer Protocol (FTP), and Hypertext Transfer Protocol (HTTP).

In information technology, a protocol (from the Greek protocollon, which was a leaf of paper glued to a manuscript volume, describing its contents) is the special set of rules that end points in a telecommunication connection use when they communicate. Protocols exist at several levels in a telecommunication connection. For example, there are protocols for the data interchange at the hardware device level and protocols for data interchange at the application program level. In the standard model known as Open Systems Interconnection (OSI), there are one or more protocols at each layer in the telecommunication exchange that both ends of the exchange must recognize and observe. Protocols are often described in an industry or international standard.

HTTP The Hypertext Transfer Protocol (HTTP) is a networking protocol for distributed, collaborative, hypermedia information systems. HTTP is the foundation of data communication for the World Wide Web. Short for HyperText Transfer Protocol, the underlying protocol used by the World Wide Web. HTTP defines how messages are formatted and transmitted, and what actions Web servers and browsers should take in response to various commands. For example, when you enter a URL in your browser, this actually sends an HTTP command to the Web server directing it to fetch and transmit the requested Web page.

File Transfer Protocol File Transfer Protocol (FTP) is a standard network protocol used to transfer files from one host to another host over a TCP-based network, such as the Internet. FTP is built on a client-server architecture and utilizes separate control and data connections between the client and server.[1] FTP users may authenticate themselves using a clear-text sign-in protocol but can connect anonymously if the server is configured to allow it.

The first FTP client applications were interactive command-line tools, implementing standard commands and syntax. the protocol for exchanging files over the Internet. FTP works in the same way as HTTP for transferring Web pages from a server to a user's browser and SMTP for transferring electronic

mail across the Internet in that, like these technologies, FTP uses the Internet's TCP/IP protocols to enable data transfer.

FTP is most commonly used to download a file from a server using the Internet or to upload a file to a server (e.g., uploading a Web page file to a server).

HTML Hypertext Markup Language (HTML) is the predominant markup language for web pages.

HTML elements are the basic building-blocks of webpages.

HTML is written in the form of HTML elements consisting of tags, enclosed in angle brackets (like <html>), within the web page content. HTML tags most commonly come in pairs like <h1> and </h1>, although some tags, known as empty elements, are unpaired, for example <img>. The first tag in a pair is the start tag, the second tag is the end tag (they are also called opening tags and closing tags). In between these tags web designers can add text, tags, comments, and other types of text-based content.

The purpose of a web browser is to read HTML documents and compose them into visible or audible web pages. The browser does not display the HTML tags, but uses the tags to interpret the content of the page.

World Wide Web The World Wide Web (abbreviated as WWW or W3 and commonly known as the Web) is a system of interlinked hypertext documents accessed via the Internet. With a web browser, one can view web pages that may contain text, images, videos, and other multimedia and navigate between them via hyperlinks.

Using concepts from earlier hypertext systems, British engineer and computer scientist Sir Tim Berners-Lee, now Director of the World Wide Web Consortium (W3C), wrote a proposal in March 1989 for what would eventually become the World Wide Web.[1] At CERN in Geneva, Switzerland, Berners-Lee and Belgian computer scientist Robert Cailliau proposed in 1990 to use hypertext "... to link and access information of various kinds as a web of nodes in which the user can browse at will",[3] and they publicly introduced the project in December.

Wireless Application Protocol Wireless Application Protocol (WAP) is a technical standard for accessing information over a mobile wireless network. A WAP browser is a web browser for mobile devices such as mobile phones (called "cellular phones" in some countries) that uses the protocol.

Before the introduction of WAP, mobile service providers had limited opportunities to offer interactive data services, but needed interactivity to support Internet and Web applications such as:

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Email by mobile phone Tracking of stock-market prices

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Sports results

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News headlines

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Music downloads Different methods used to communicate

methods used to communicate on the web. It is important to understand the nuances and benefits of the different forms.

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Email This is the most popular communication method. Users typically use desktop software to receive, read and respond to messages. Some users use web-based mail and manage messages in a web browser like Internet Explorer. The downfall to email communication is that anyone can send email messages to anyone else if they have (or guess) the correct email address. This system's Achilles heel is its simplicity and universal popularity.

Email accounts are often burdened by spam or unsolicited email. Despite software developers having created complex spam filters and legislators having introduced new anti-spam legislation, the problem persists and spam continues to burden email as a messaging medium.

Instant Messaging Instant messaging allows users to "chat" in real time. Users can send text messages to anyone online and receive instant replies if the user is also online. The "instant" fad gave way to parental fears as children made "friends" online. With no way to confirm if "friends" are who they represent themselves to be, and multiple security holes, instant messaging has taken a back seat in internet communication.

Blogs Online journals and daily diaries have taken hold. Some blogs are interactive, allowing users to respond and comment on posts. Locating topic-specific blogs that provide relevant and interesting content on a daily basis can be a challenge. The nature of a blog is to contain fresh public content. As our lives become more complicated blogs are often abandoned, as they require constant updating.

Social networking: Social networking is the grouping of individuals into specific groups, like small rural communities or a neighborhood subdivision, if you will. Although social networking is possible in person, especially in the workplace, universities, and high schools, it is most popular online. When it comes to online social networking, websites are commonly used. These websites are known as social sites.

IP address An Internet Protocol address (IP address) is a numerical label assigned to each device (e.g., computer, printer) participating in a computer network that uses the Internet Protocol for communication.[1] An IP address serves two principal functions: host or network interface identification and location addressing. Its role has been characterized as follows: "A name indicates what we seek. An address indicates where it is. A route indicates how to get there."[2] Every machine on the Internet has a unique identifying number, called an IP Address. A typical IP address looks like this: • 216.27.61.137 • History of internet •

History of internet: Before there was the public internet there was the internet's forerunner ARPAnet or Advanced Research Projects Agency Networks. ARPAnet was funded by the United States military after the cold war with the aim of having a military command and control center that could withstand nuclear attack. The point was to distribute information between geographically dispersed computers. ARPAnet created the TCP/IP communications standard, which defines data transfer on the Internet today. The ARPAnet opened in 1969 and was quickly usurped by civilian computer nerds who had now found a way to share the few great computers that existed at that time.

Orpanet, the first internet: "The Internet may fairly be regarded as a never-ending worldwide conversation." - supreme judge statement on considering first amendment rights for Internet users.

On a cold war kind of day, in swinging 1969, work began on the ARPAnet, grandfather to the Internet. Designed as a computer version of the nuclear bomb shelter, ARPAnet protected the flow of information between military installations by creating a network of geographically separated computers that could exchange information via a newly developed protocol (rule for how computers interact) called NCP (Network Control Protocol).

History of internet according to years of inventions 1969: Arpanet 1969: Unix 1970: Arpanet network 1971: Email 1973: The first trans-Atlantic connection and the popularity of emailing

1974: The beginning of TCP/IP 1975: The email client 1977: The PC modem 1978: The Bulletin Board System (BBS) 1978: Spam is born 1979: MUD â&#x20AC;&#x201C; The earliest form of multiplayer games 1979: Usenet 1980: ENQUIRE software 1982: The first emoticon 1983: Arpanet computers switch over to TCP/IP 1984: Domain Name System (DNS) 1985: Virtual communities 1986: Protocol wars 1987: The Internet grows 1988: IRC â&#x20AC;&#x201C; Internet Relay Chat 1988: First major malicious internet-based attack 1989: AOL is launched 1989: The proposal for the World Wide Web 1990: First commercial dial-up ISP 1990: World Wide Web protocols finished 1991: First web page created 1991: First content-based search protocol 1991: MP3 becomes a standard

1991: The first webcam 1993: Mosaic â&#x20AC;&#x201C; first graphical web browser for the general public 1993: Governments join in on the fun 1994: Netscape Navigator 1995: Commercialization of the internet 1995: Geocities, the Vatican goes online, and JavaScript 1996: First web-based (webmail) service 1997: The term "weblog" is coined 1998: First new story to be broken online instead of traditional media 1998: Google!

1998: Internet-based file-sharing gets its roots 1999: SETI@home project 2000: The bubble bursts 2001: Wikipedia is launched 2003: VoIP goes mainstream

2003: MySpace becomes the most popular social network 2003: CAN-SPAM Act puts a lid on unsolicited emails 2004: Web 2.0 2004: Social Media and Digg

2004: "The" Facebook open to college students

Facebook launched in 2004, though at the time it was only open to college students and was called "The Facebook"; later on, "The" was dropped from the name, though the URL http://www.thefacebook.com still works.

2005: YouTube â&#x20AC;&#x201C; streaming video for the masses YouTube launched in 2005, bringing free online video hosting and sharing to the masses.

2006: Twitter gets twittering Twitter launched in 2006. It was originally going to be called twittr (inspired by Flickr); the first Twitter message was "just setting up my twttr".

The biggest innovation of 2007 was almost certainly the iPhone, which was almost wholly responsible for renewed interest in mobile web applications and design.