ecom notes mca 5th sem


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ecom notes mca 5th sem

  1. 1. What role does a modem play in Internet? Connecting to the Internet using a computer modem is the most widely available method of connecting to the Internet. Although connecting to the Internet with a modem is a much cheaper solution A modem stands for modulation demodulation. A modem basically converts analog signals to digital signals or vice versa. This conversion is required because the subscriber line through which you are getting your internet, carries analog signals. But, a computer understands only digital signals. So the conversion to digital signals is required. Also it has to be changed back to analog signals because analog signals can go longer distances through your subscriber line. 1.3 Flat Name Space In a flat name space, a name is assigned to an address. A name in this space is a sequence of characters without structure. The names may or may not have a common section; if they do, it has no meaning. The main disadvantage of a flat name space is that it cannot be used in a large system such as the Internet because it must be centrally controlled to avoid ambiguity and duplication. Each host given a name Special file to keep name-address mapping (ex. /etc/hosts file in Linux) All hosts must know the current mapping for all other hosts with which they want to communicate Central authority to maintain authoritative host file with which all other hosts sync (ex. HOSTS.TXT at NIC in the old days) Makes the hostname file too large and the entire scheme unmanageable and impractical in any large network (ex., Internet). Flat Name Architecture (Flat Name Space) Names are assigned as a sequence of symbols that are interpreted as a single, whole label without any internal structure. There is no clear relationship between any name and any other name. Figure 232: Flat Name Architecture (Flat Name Space) This diagram shows an example of a flat name architecture. There is no structure that organizes the names or dictates how they must be constructed. Logically, each device is a peer of each of the others.
  2. 2. Hierarchical Name Architecture (Hierarchical or Structured Name Space) In this architecture, while names consist of a sequence of symbols, these symbols are assigned using a specific and clear structure. The name consists of discrete elements that are related to each other usually using hierarchical “parent/child” semantics. There are many naming architectures in various contexts that use this type of hierarchical structure; for example, consider how a large company might set up an organization chart and name the executives and officers in the organization. Figure 233 Figure 233: Hierarchical Name Architecture (Structured Name Space) In this case, the organization has chosen to structure its device names first by facility location, and then by department. Each name starts with something like “USA-Service-” or “EU-Mfg-”. This provides immediate benefits by providing local control over device naming without risk of conflicts. The structure also makes it easier to know immediately where a device can be found within the organization.
  3. 3. internet The Internet is a global network connecting millions of computers. More than 100 countries are linked into exchanges of data, news and opinions. According to Internet World Stats, as of December 31, 2011 there was an estimated 2,267,233,742 Internet users worldwide. This represents 32.7% of the world's population. There are a variety of ways to access the Internet. Most online services offer access to some Internet services. It is also possible to gain access through a commercial Internet Service Provider (ISP). The term Internet today refers to the global network of public computers running Internet Protocol The term "Internet" was originally coined in the 1970s.Throughout the 1970s, 1980s, and 1990s, a number of smaller national networks like ARPANET, BITNET, CSNET, and NSFNET evolved, merged, or dissolved, then finally joined with non-US networks to form the global Internet. The Internet is now maintained by the major Internet service providers such as MCI Worldcom, Sprint, GTE, ANS, and UUNET. Many people think the Internet and the World Wide Web are the same thing. They're not! The World Wide Web is what you are browsing right now. It is one of the many features of the Internet. E-mail, FTP, and Instant Messaging are also features of the Internet. EXTRANET is an extension of an organization’s intranet that can be accessed by users outside the organization, usually partners, vendors, and suppliers with a username and password to access the intranet. The World Wide Web, or simply Web, is a way of accessing information over the medium of the Internet. It is an information-sharing model that is built on top of the Internet. internet Intranet Internet is the worldwide interconnection of all smart communication devices that have a valid IP. intranet is a privately owned part of the internet under which only a selected number of IPs are allowed to communicate. internet the information is shared world wide with any public user to explain in simple terms information shared in intranet can be access only by authorized persons especially members or employees of the organization or company intranet is private, within the organization internet is public available for global access Intranets can help users to locate and view information faster and use app. relevant to their roles and responsibilities Communication: Intranets can serve as powerful tools for communication within an organization, vertically and horizontally Low maintenance With information residing in only one place - the Web server - it is relatively easy and affordable to add new information or to update existing information and make it instantly available.
  4. 4. Differences in Internet & Intranet Internet is general to PCs all over the world where Intranet is specific to few PCs. Internet is wider access and provides a better access to websites to large population whereas Intranet is restricted. Internet is not as safe as Intranet as Intranet can be safely privatized as per the need. Internet is network of Computers which is open for all. Internet itself contains a large number of intranets. Unlimited number of users. Visitors traffic is unlimited. Contains unlimited source of information. Collection of various LANs, WANs and MANs. What is a Network Protocol A protocol is a set of rules that governs the communications between computers on a network. These rules include guidelines that regulate the following characteristics of a network: access method, allowed physical topologies, types of cabling, and speed of data transfer. Definition: A network protocol defines rules and conventions for communication between network devices. Protocols for computer networking all generally use packet switchingtechniques to send and receive messages in the form of packets. Network protocols include mechanisms for devices to identify and make connections with each other, as well as formatting rules that specify how data is packaged into messages sent and received. Types of Network Protocols The most common network protocols are: Ethernet Local Talk FDDI ATM Internet Protocol (IP) ,higher-level protocols like TCP, UDP, HTTP, and FTPall integrate with IP to provide additional capabilities. Similarly, lower-level Internet Protocols like ARP and ICMP also co-exist with IP. Ethernet The Ethernet protocoluses an access method called CSMA/CD (Carrier Sense Multiple Access/Collision Detection). This is a system where each computer listens to the cable before sending anything through the network. If the network is clear, the computer will transmit. If some other node is already transmitting on the cable, the computer will wait and try again when the line is clear. Sometimes, two computers attempt to transmit at the same instant. When this happens a collision occurs. Each computer then backs off and waits a random amount of time before attempting to retransmit. With this access method, it is normal to have collisions. However, the delay caused by collisions and retransmitting is very small and does not normally effect the speed of transmission on the network.The Ethernet protocol allows for linear bus, star, or tree topologies. Data can be transmitted over wireless access points, twisted pair, coaxial, or fiber optic cable at a speed of 10 Mbps up to 1000 Mbps.
  5. 5. Fast Ethernet To allow for an increased speed of transmission, the Ethernet protocol has developed a new standard that supports 100 Mbps. This is commonly called Fast Ethernet. Fast Ethernet requires the use of different, more expensive network concentrators/hubs and network interface cards. In addition, category 5 twisted pair or fiber optic cable is necessary. Fast Ethernet is becoming common in schools that have been recently wired. Local Talk Local Talk is a network protocol that was developed by Apple Computer, Inc. for Macintosh computers. The method used by Local Talk is called CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance). It is similar to CSMA/CD except that a computer signals its intent to transmit before it actually does so. Local Talk adapters and special twisted pair cable can be used to connect a series of computers through the serial port. The Local Talk protocol allows for linear bus, star, or tree topologies using twisted pair cable. A primary disadvantage of Local Talk is speed. Its speed of transmission is only 230 Kbps. FDDI Fiber Distributed Data Interface (FDDI) is a network protocol that is used primarily to interconnect two or more local area networks, often over large distances. The access method used by FDDI involves token-passing. FDDI uses a dual ring physical topology. Transmission normally occurs on one of the rings; however, if a break occurs, the system keeps information moving by automatically using portions of the second ring to create a new complete ring. A major advantage of FDDI is speed. It operates over fiber optic cable at 100 Mbps. ATM Asynchronous Transfer Mode (ATM) is a network protocol that transmits data at a speed of 155 Mbps and higher. ATM works by transmitting all data in small packets of a fixed size; whereas, other protocols transfer variable length packets. ATM supports a variety of media such as video, CD-quality audio, and imaging. ATM employs a star topology, which can work with fiber optic as well as twisted pair cable. ATM is most often used to interconnect two or more local area networks. It is also frequently used by Internet Service Providers to utilize high-speed access to the Internet for their clients. As ATM technology becomes more costeffective, it will provide another solution for constructing faster local area networks. DHCP allows a computer to join an IP-based network without having a pre-configured IP address. DHCP is a protocol that assigns unique IP addresses to devices, then releases and renews these addresses as devices leave and re-join the network. Internet service providers usually use DHCP to help customers join their networks with minimum setup effort required. Likewise, home network equipment like broadband routersoffers DHCP support for added convenience in joining home computers to local area networks (LANs). DHCP environments require a DHCP server set up with the appropriate configuration parameters for the given network. Key DHCP parameters include the range or "pool" of available IP addresses, the correct subnet masks, plus network gateway and name server addresses. Devices running DHCP client software can then automatically retrieve these settings from DHCP servers as needed. DHCP clients are built into all common network operating systems. Using DHCP on a network means system administrators do not need to configure these parameters individually for each client device.
  6. 6. The TCP/IP Networking Protocol Suite TCP/IP, the protocol on which the Internet is built, is actually not a single protocol but rather an entire suite of related protocols. TCP is even older than Ethernet. It was first conceived in 1969 by the Department of Defense. Currently, the Internet Engineering Task Force, or IETF, manages the TCP/IP protocol suite. IP IP, which stands for Internet Protocol, is a Network layer protocol that is responsible for delivering packets to network devices. The IP protocol uses logical IP addresses to refer to individual devices rather than physical (MAC) addresses. A protocol called ARP (for Address Resolution Protocol) handles the task of converting IP addresses to MAC addresses. Because IP addresses consist of a network part and a host part, IP is a routable protocol. As a result, IP can forward a packet to another network if the host is not on the current network. (The ability to route packets across networks is where IP gets its name. An internet is a series of two or more connected TCP/IP networks that can be reached by routing.) TCP TCP, which stands for Transmission Control Protocol,is a connection-oriented Transport layer protocol. TCP lets a device reliably send a packet to another device on the same network or on a different network. TCP ensures that each packet is delivered if at all possible. It does so by establishing a connection with the receiving device and then sending the packets. If a packet doesn't arrive, TCP resends the packet. The connection is closed only after the packet has been successfully delivered or an unrecoverable error condition has occurred. One key aspect of TCP is that it's always used for one-to-one communications. In other words, TCP allows a single network device to exchange data with another single network device. TCP is not used to broadcast messages to multiple network recipients. Instead, the User Datagram Protocol (UDP) is used for that purpose. Many well-known Application layer protocols rely on TCP. For example, when a user running a Web browser requests a page, the browser uses HTTP to send a request via TCP to the Web server. When the Web server receives the request, it uses HTTP to send the requested Web page back to the browser, again via TCP. Other Application layer protocols that use TCP include Telnet (for terminal emulation), FTP (for file exchange), and SMTP (for e-mail). UDP The User Datagram Protocol (or UDP) is a connectionless Transport layer protocol that is used when the overhead of a connection isn't required. After UDP has placed a packet on the network (via the IP protocol), it forgets about it. UDP doesn't guarantee that the packet actually arrives at its destination. Most applications that use UDP simply wait for any replies expected as a result of packets sent via UDP. If a reply doesn't arrive within a certain period of time, the application either sends the packet again or gives up. Probably the best-known Application layer protocol that uses UDP is DNS, the Domain Name System. When an application needs to access a domain name such as, DNS sends a UDP packet to a DNS server to look up the domain. When the server finds the domain, it returns the domain's IP address in another UDP packet. The TCP/IP Internet protocols consist of: Transmission Control Protocol (TCP), which uses a set of rules to exchange messages with other Internet points at the information packet level Internet Protocol (IP), which uses a set of rules to send and receive messages at the Internet address level Additional protocols that include the Hypertext Transfer Protocol (HTTP) and File Transfer Protocol (FTP), each with defined sets of rules to use with corresponding programs elsewhere on the Internet
  7. 7. DNS - Domain Name System - translates network address (such as IP addresses) into terms understood by humans (such as Domain Names) and vice-versa DHCP - Dynamic Host Configuration Protocol - can automatically assign Internet addresses to computers and users FTP - File Transfer Protocol - a protocol that is used to transfer and manipulate files on the Internet HTTP - HyperText Transfer Protocol - An Internet-based protocol for sending and receiving webpages IMAP - Internet Message Access Protocol - A protocol for e-mail messages on the Internet IRC - Internet Relay Chat - a protocol used for Internet chat and other communications POP3 - Post Office protocol Version 3 - a protocol used by e-mail clients to retrieve messages from remote servers SMTP - Simple Mail Transfer Protocol - A protocol for e-mail messages on the Internet Also Known As: Dynamic Host Configuration Protoco Definition: Frame relay is a data link network protocol designed to transfer data on Wide Area Networks (WANs). Frame relay works over fiber optic or ISDN lines. The protocol offers low latency and to reduce overhead, does perform any error correction, which is instead handled by other components of the network. Frame relay has traditionally provided a cost-effective way for telecommunications companies to transmit data over long distances. Frame relay has decreased in popularity as companies are gradually migrating their deployments to Internet Protocol (IP) based solutions. Definition: ICMP is a network protocol useful in Internet Protocol (IP) network management and administration. ICMP is a required element of IP implementations. ICMP is a control protocol, meaning that it does not carry application data, but rather information about the status of the network itself. ICMP can be used to report: errors in the underlying communications of network applications availability of remote hosts network congestion Also Known As: Internet Control Message Protocol Global.asa file The Global.asa file is an optional file that can contain declarations of objects, variables, and methods that can be accessed by every page in an ASP application. All valid browser scripts (JavaScript, VBScript, JScript, PerlScript, etc.) can be used within Global.asa. The Global.asa file can contain only the following: Application events Session events <object> declarations TypeLibrary declarations
  8. 8. the #include directive The Global.asa file must be stored in the root directory of the ASP application, and each application can only have one Global.asa file. Events in Global.asa In Global.asa you can tell the application and session objects what to do when the application/session starts and what to do when the application/session ends. The code for this is placed in event handlers. The Global.asa file can contain four types of events: Application_OnStart - Occurs when the FIRST user calls the first page in an ASP application. This event occurs after the Web server is restarted or after the Global.asa file is edited. The "Session_OnStart" event occurs immediately after this event. Session_OnStart - This event occurs EVERY time a NEW user requests his or her first page in the ASP application. Session_OnEnd - This event occurs EVERY time a user ends a session. A user-session ends after a page has not been requested by the user for a specified time (by default this is 20 minutes). Application_OnEnd - This event occurs after the LAST user has ended the session. Typically, this event occurs when a Web server stops. This procedure is used to clean up settings after the Application stops, like delete records or write information to text files. Restrictions Restrictions on what you can include in the Global.asa file: You cannot display text written in the Global.asa file. This file can't display information You can only use Server and Application objects in the Application_OnStart and Application_OnEnd subroutines. In the Session_OnEnd subroutine, you can use Server, Application, and Session objects. In the Session_OnStart subroutine you can use any built-in object What is Gopher? Gopher was developed at the University of Minnesota and named after the school's mascot. Gopher is an older distributed information retrieval system, similar to but much simpler than theWorld Wide Web . Gopher did not offer a way to create free-form hypertext documents similar to HTML. Gopher did offer a very structured and useful approach to retrieving information and searching across many Gopher sites. Gopher is software that enables you to gain easy access to documents and databases worldwide, via the Internet, using your home or office computer. The gopher system allows people to search for and retrieve information using a text interface. The technology is based on a client-server structure, where a gopher client program is used to search gopher servers. These servers can store documents, articles, programs, and other
  9. 9. information. Instead of hyperlinks, the gopher interface uses menus of links to other documents and programs. Attributes Interface: Menu-driven hierarchy Form: Integrated Medium: Simple Text or Binary Distribution: Public Administration: Moderated Similar Tools: World Wide Web Dependent Tools: Telnet, FTP, Veronica Advantages and Disadvantages of "Internet and World Wide Web" The advantage of using internet and WWW is first you can easily get information through internet and it‟s always accessible. The disadvantage of using internet and WWW is first you can get virus online especially if your computer does not have an anti-virus, your computer can get virus like opening some website or etc. Secondly you can be scam by the people who are professional scammer . Other disadvantage is your “Personal Information” can be accessed by other people if you use the Internet, your personal information such as your name, address, etc. and sometimes if you use a credit card to shop online, then your credit card information can also be “stolen.” The disadvantages of the world wide web mainly center around the potential public accessibility of private information. Whenever a person gets on to the world wide web, they always run the risk of their private information getting into the wrong hands. Another disadvantage is that they are not doing other things that are actually more important than surfing, such as regular physical activity and spending time with friends and family. 3. PITFALLS IN USING THE WEB AS AN INFORMATION SOURCE 3.1. Authority The Internet is a distributed environment, with no overall authority. In practical terms, this means that no standards exist for content or format, and anyone can be an author or publisher. At the least, this can result in typographical and grammatical errors, misspellings, and poor layout and design,information can be misleading or erroneous. 3.2. Content/Scope Though an enormous amount of data is transmitted daily across the web. Much of what is available on the web is of little or no value, and the sheer quantity of sites makes the search for quality that much more difficult.Information is more likely to be current than historical.
  10. 10. 3.3. Stability we find a highly unstable environment where sites can come and go with alarming ease. Web sites are notorious for changing location and leave no "forwarding address," or disappearing altogether.. With heavy traffic, servers become overloaded and access is delayed or denied. the issue of reliability lies at the heart of concerns over the web. Dubious content, questionable integrity, inaccessible servers, unmaintained sites, difficulty in finding relevant information, and unpredictable costs all conspire to discourage reliance upon using the web as one uses a library. 4. BENEFITS OF USING THE WEB 4.1. Timeliness One of the web's strongest assets is its ability to provide current and timely information. Sites with business data (currency exchange rates, stock market data), geo-political information, weather, and current news exploit the webs potential to provide information with an immediacy. 4.2. Interactivity The web's interactive capabilities provide functions not possible through standard print sources. An increasing number of sites have interactive features where calculations such as unit conversion (, local times around the world (, and distance calculations ( are performed automatically. Guidelines are provided and users submit question on online form or initiate an interactive reference session. .4.3. Multimedia and Hypertext Capabilities Web sites provide for true integration of text, sound, and image, including video, for example, the web hosts dictionaries which include audio pronunciation guides, and sites which integrate music and dance clips into the text. Moreover, with its dynamic system of links, the web is able to draw related materials and information together . 4.4. Availability The web offers greater flexibility regarding where and when its information can be accessed. While achieving this capability requires powerful and properly configured hardware, necessary software, and ability to connect to the network. The web offers the advantage of simultaneous use by multiple users. formatdatetime function The Format Date Time function takes two arguments: a date and (optional) an integer from 0 through 4. The meanings of these numbers are as follows: 0 - This is the default setting. A short date DD/MM/YYYY will be used. 1 - A long date defined by the computer's regional settings. 2 - A short date defined by the regional settings. 3 - (time)A time using the time format defined by the regional settings. 4 - (time)A time using military time HH:MM (H = hour, M = Minute) examples <%= FormatDateTime(Date) %><br> <%= FormatDateTime(Date, 0) %><br> <%= FormatDateTime(Date, 1) %><br> <%= FormatDateTime(Date, 2) %><br> <%= FormatDateTime(Now, 3) %><br>
  11. 11. <%= FormatDateTime(Now, 4) %><br> <%= FormatDateTime(Now) %><br> You should get values similar to this. (They will be based on the current date when you run them though.) 4/18/2005 4/18/2005 Monday, April 18, 2005 4/18/2005 2:08:24 PM 14:08 4/18/2005 2:08:24 PM Extranet An extranet is a computer network that allows controlled access from the outside, for specific business or educational purposes. In a business-to-businesscontext, an extranet can be viewed as an extension of an organization's intranet that is extended to users outside the organization, usually partners, vendors and suppliers, in isolation from all other Internet users. In contrast, business-to-consumer (B2C) models involve known servers of one or more companies, communicating with previously unknown consumer users. An extranet is similar to a DMZ in that it provides access to needed services for channel partners, without granting access to an organization's entire network. Advantages[edit] No Hardware/Software. There's no software to install, no servers to maintain, no experts to hire! Instant Setup & Deployment. Sign up online and get started near instantly! Pay-as-you-go Pricing. Access enterprise collaboration solutions for a low monthly per user fee. Feature Rich. Get the power of an enterprise class extranet solution. Set up unlimited extranets with custom desktop, announcements, document management, calendars, task management, contact directories, forums, polls, IM and more! Extranet Portal Customization. You can easily publish unlimited extranets tailored to user needs. Finely manage branding, look, layout, organization, collaboration tools and membership. You need no expertise at all! Remote Access. Your teams, partners and clients can access the extranet from any web enabled PC, Mac or mobile device. Completely Secure. We guarantee 99.9% reliability through our secure, offsite data center facilities equipped with redundant servers. Free Webinars & Support. When we say we offer a hassle free solution, we mean it! We are always around to assist you. Exchange large volumes of data using Electronic Data Interchange (EDI) Share product catalogs exclusively with trade partners Collaborate with other companies on joint development efforts Jointly develop and use training programs with other companies Provide or access services provided by one company to a group of other companies, such as an online banking application managed by one company on behalf of affiliated banks Disadvantages[edit] Extranets can be expensive to implement and maintain within an organization (e.g., hardware, software, employee training costs), if hosted internally rather than by an application service provider. Security of extranets can be a concern when hosting valuable or proprietary information.
  12. 12. What is JavaScript JavaScript is a programming language that uses scripts to perform tasks. It was first developed as way to create more interesting web pages that could also be interactive. Along with adding interaction to pages on a website, it can also link together different web based programs such as HTML pages. JavaScript is used to modify forms, open new web pages, and create dynamic content on a web page. It uses a system of variables, operators, control structures, and functions to create a user-friendly interactive web page. How is JavaScript Used JavaScript is used to make websites interactive. HTML was developed for the sole purpose of giving the user the ability to view documents. The problem with HTML and its static presence is that computers are capable of much more. With JavaScript, an HTML page can be turned into an interactive tool. JavaScript can be added to an HTML document in three different ways. The most common way is to embed the code between two script tags. A specific JavaScript code can also be placed right within an HTML tag. A code can also be placed in a completely different file. The code is then called over to the HTML page by using an SRC attribute. Creating Dynamic Content JavaScript has many benefits, including the ability to create web content that is dynamic and interactive as opposed to hard coded content. The “write” function is one way that web developers are able to do this. Using the “write” function allows different text to be shown depending on user’s preferences or their answers to questions. Dynamic content can be a script that can be programmed to show something different every time a page loads. JavaScript is also used to create the advertisements on websites, alerts, and the security features that some websites have for their users to sign in. When an image on a page changes as the mouse moves over it, it is because of JavaScript. This can be used to draw the attention of the user to a specific link. Other Features of JavaScript JavaScript has many different features. It has the ability to detect a user’s browser and operating system. This allows the script to perform specific tasks related to a specific browser. All browsers have accepted the scripting language of JavaScript and they all provide support for it. Other languages may need a flash plugin in order to see flash content. Since all browsers support JavaScript, there is no need for this. JavaScript is a functional programming language. This means that it uses functions to perform tasks. These functions can be manipulated and can be connected to other functions for an unlimited scope of possibilities. JavaScript can also validate input from users. If they put in the wrong information, they will get an error message. This can be done right on the user’s web browser. Other programming languages have to wait for server access.
  13. 13. JavaScript Features In this JavaScript tutorial, you will learn about features of JavaScript, JavaScript as a programming tool, dynamic effects, browser detection, DOM control and other popular JavaScript features. A Great Programming Tool for HTML: Professional Web designers are undoubtedly adept in using HTML and proficient in website design but not necessarily skillful in computer programming. JavaScript is a programming tool for such a situation. JavaScript is a powerful scripting language that helps HTML designers to effectively and interactively design websites and web pages in a very simple and efficient way. Handles Dynamic Effects: JavaScript is such a powerful scripting language which has features to achieve dynamic effects in web pages. Using the features available in JavaScript, the designer can decide to have dynamically placed text at run time. Browser Detection: One of the powerful feature of JavaScript is its ability to detect client browser. Browser detection feature of JavaScript helps to achieve independent platforms. JavaScript can detect the type of browser the visitor is using and programatically switch the page to show customised pages designed for different browsers. Thus by making use of browser detection feature of JavaScript, the designer gets better control over the browser. Saves Time: JavaScript also has the feature of validating data submitted at the client level. This helps in saving the processing time of the server because JavaScript initially creates the validation on the client side. DOM: Client side JavaScript is embedded inside HTML This embedded JavaScript is used along with DOM (Document Object Model) for control over the browser by means of objects. Popular Scripting language: JavaScript has simple rules and procedures that make it easier to use and learn for programmers. This has made JavaScript a popular client-side scripting language. Interpreted Language: It is an interpreted language, meaning that it can be used or executed with ease without pre-compilation. Visual JavaScript: Visual JavaScript is a component-based visual development tool for the Netscape Open Network Environment used by programmers who want to build cross-platform web-based applications. Generators and Iterators: The newer version of JavaScript features built-in Generators and Iterators. There are other important features in JavaScript such as variables, arrays, objects, methods, event handlers, etc. which will be explained in detail in the following sections of this tutorial.
  14. 14. Database Connectivity Database Connectivity Connecting and communicating between an application and a database system. Open DataBase Connectivity, astandard database access method developed by the SQL Access group in 1992. Open Database Connectivity (ODBC) is an interface standard for accessing data and communicating with database systems, regardless of the operating system (OS), database system (DS) or programming language. This is accomplished by using ODBC drivers that serve as a bridge between applications and database systems. Open Database Connectivity (ODBC) is an open standard application programming interface (API) for accessing a database. By using ODBC statements in a program, you can access files in a number of different databases, including Access, dBase, DB2, Excel, and Text. In addition to the ODBC software, a separate module or driver is needed for each database to be accessed PURPOSE The purpose of ODBC is to make it possible to access any data from any application, regardless of which database management system (DBMS) is handling the data. ODBC manages this by inserting a middle layer, called a database driver , between an application and the DBMS. The purpose of this layer is to translate the application's data queries into commands that the DBMS understands. For this to work, both the application and the DBMS must be ODBC-compliant -- that is, the application must be capable of issuing ODBC commands and the DBMS must be capable of responding to them. ODBC is interface for accessing data in a heterogeneous environment of relational and non- relational database management systems. ODBC purpose is to provides a universal data access interface. It allows developers to use the same coding conventions regardless of the actual database platform implemented on the backend. The ODBC model contains the following three major components: Client (usually a programming application) Database Server ODBC Driver The driver’s function, which is very similar to a human translator, is to bridge the gap between parties that would not otherwise understand each other. ODBC is based on and closely aligned with The Open Group standard Structured Query Language (SQL) CallLevel Interface. It allows programs to use SQL requests that will access databases without having to know the proprietary interfaces to the databases. ODBC handles the SQL request and converts it into a request the individual database system understands.
  15. 15. ODBC was created by the SQL Access Group and first released in September, 1992. Although Microsoft Windows was the first to provide an ODBC product, versions now exist for UNIX, OS/2, and Macintosh platforms as well. EXAMPLE A good practice when using databases is to set the username, the password and the database name values at the beginning of the script code. If you need to change them later, it will be an easy task. $username="your_username";$password="your_password";$database="your_database"; You should replace "your_username", "your_password" and "your_database" with the MySQL username, password and database that will be used by your script. At this point you may be wondering if it is a security risk to keep your password in the file. You don't need to worry because the PHP source code is processed by the server before being sent to the browser. So the visitor will not see the script's code in the page source. Next you should connect your PHP script to the database. This can be done with the mysql_connect PHP function: mysql_connect(localhost,$username,$password); This line tells PHP to connect to the MySQL database server at 'localhost' (localhost is the MySQL server which usually runs on the same physical server as your script). After the connection is established you should select the database you wish to use. This should be a database to which your username has access to. This can be completed through the following command: @mysql_select_db($database) or die( "Unable to select database"); It tells PHP to select the database stored in the variable $database (in our case it will select the database "your_database"). If the script cannot connect it will stop executing and will show the error message: Unable to select database The 'or die' part is useful as it provides debugging functionality. However, it is not essential. Another important PHP function is: mysql_close(); This is a very important function as it closes the connection to the database server. Your script will still run if you do not include this function. And too many open MySQL connections can cause problems for your account. This it is a good practice to close the MySQL connection once all the queries are executed.connected
  16. 16. WEB PAGE A document on the World Wide Web.Every Web page is identified by a uniqueURL (Uniform Resource Locator). A web page or webpage is a document commonly written in HyperText Markup Language (HTML) that is accessible through the Internet or other network using a browser. A web page is accessed by entering a URL addresses and may contain text, graphics, and hyperlinks to other web pages and files. The page you're reading now is an example of a web page. A website refers to a central location that contains more than one web page. A Web page is what you see on the Net. One page with text and graphics. These can be created using HTML, DHTML and JavaScript and can be about anything the author of the page wants it to be about. PHP Session Variables A PHP session variable is used to store information about, or change settings for a user session. Session variables hold information about one single user, and are available to all pages in one application. When you are working with an application, you open it, do some changes and then you close it. This is much like a Session. The computer knows who you are. It knows when you start the application and when you end. But on the internet there is one problem: the web server does not know who you are and what you do because the HTTP address doesn't maintain state. A PHP session solves this problem by allowing you to store user information on the server for later use (i.e. username, shopping items, etc). However, session information is temporary and will be deleted after the user has left the website. If you need a permanent storage you may want to store the data in a database. Sessions work by creating a unique id (UID) for each visitor and store variables based on this UID. The UID is either stored in a cookie or is propagated in the URL. Starting a PHP Session The session_start() function must appear BEFORE the <html> tag: <?phpsession_start(); ?> <html> <body> </body> </html> The code above will register the user's session with the server, allow you to start saving user information, and assign a UID for that user's session.
  17. 17. Destroying a Session If you wish to delete some session data, you can use the unset() or the session_destroy() function. The unset() function is used to free the specified session variable: You can also completely destroy the session by calling the session_destroy() function: <?php session_destroy(); ?> Note: session_destroy() will reset your session and you will lose all your stored session data. A “session” is set for maintaining the user data as the person is browsing through the site. A session is very useful in e-commerce websites, social networking sites etc. In PHP, session variables are used to set the sessions. Anything can be set / stored in a session like the user‟s id, username, some encrypted password string etc. A session is always stored in the server. You lose all the session data once you close your browser, as every time you re-open your browser, a new session starts for any website. Example: $_SESSION[„customer_name‟] = „John‟; A “cookie” is however different from a session. It stores some information like the username, last visited pages etc. So that when the customer visits the site again, he may have the same environment set for him. You can store almost anything in a browser cookie. A cookie is stored in the client‟s browser. Like, when you check the „Remember Password‟ link on any website, a cookie is set in your browser, which exists there in the browser until manually deleted. So, when you visit the same website again, you don‟t have to re-login. But, it can also be problematic at times, if the user has blocked cookies in his browser and you have a shopping site that utilizes cookies to store the data. Then, that person will never be able to shop from your website. Example: setcookie("username", "John", time()+2400); The main difference between cookies and sessions is that cookies are stored in the user's browser, and sessions are not. This difference determines what each is best used for. Difference between Client side-scripting and Server side-scripting Server-side code executes on the server and client side code runs on the client browser. Server side validation can be done on server side using server controls, but the client-side validation can be done through the browser. Client-side validation can be done with JavaScript or VB Script. Client-side scripts are interpreted by the browser. Client-side scripting generally refers to the class of computer programs on the web that are executed client-side. Client side scripts are executed and changed
  18. 18. by the user on his side. server-side handles logging in, personal information and preferences and provides the specific data which the user wants. Server side scripting is when the users browser makes a request back to the server and the script creates the dynamic page based a number of conditions Server side scripting is when the users browser makes a request back to the server and the script creates the dynamic page based a number of conditions. Languages usually used are PHP or ASP. Example: On a website and the user clicks on the show the products link. The server then runs the PHP/ASP code to create a page by finding all the products in the data base. The page is created and sent back to the users browser for viewing. Client side scripting is when all the code is already on the users browser and the page alters based on the users input. Language is usually JavaScript. Example: A JavaScript drop down menu. The JavasScript alters how the menu is displayed but all the code is run locally while it is doing it. Client-Side vs. Server-Side Code: What’s the Difference? by Bill Fote May 1st, 2013 Server-Side Client-Side Web Development Ajax Web Apps Web Applications In web applications, there is the client and the server. The “client” is a web browser, like Internet Explorer, Google Chrome, Firefox, etc. The “server” is a web application server at a remote location that will process web requests and send pages to the client. Web applications can contain code that is processed on the client’s browser or on the web server. However, web applications have a disconnected architecture, which means that there is never a live, constant connection between the page displayed in the client’s browser and a web or database server. The majority of the processing will be done at the server and not on the client’s internet browser. When a database needs to be accessed on a server, the web application will post the page back to the web server and server-side code will process the request. In order to fully understand the web application’s architecture, we must understand postback and the page life cycle, which I have discussed more extensively in previous articles.
  19. 19. Server-Side Code There are several server-side technologies that can be used when developing web applications. The most popular is Microsoft’s ASP.NET. In ASP.NET, server-side code uses the .NET Framework and is written in languages like C# and VB.NET. Server-side processing is used to interact with permanent storage like databases or files. The server will also render pages to the client and process user input. Server-side processing happens when a page is first requested and when pages are posted back to the server. Examples of server-side processing are user validation, saving and retrieving data, and navigating to other pages. The disadvantage of server-side processing is the page postback: it can introduce processing overhead that can decrease performance and force the user to wait for the page to be processed and recreated. Once the page is posted back to the server, the client must wait for the server to process the request and send the page back to the client. Client-Side Code The benefits of client-side processing in an ASP.NET web application are programming languages like C# and VB.NET along with the .NET Framework. Languages like C# and VB.NET sit on top of the .NET framework and have all the benefits of object oriented architectures like inheritance, implementing interfaces and polymorphism. In contrast to server-side code, client-side scripts are embedded on the client’s web page and processed on the client’s internet browser. Client-side scripts are written in some type of scripting language like JavaScript and interact directly with the page’s HTML elements like text boxes, buttons, list-boxes and tables. HTML and CSS (cascading style sheets) are also used in the client. In order for client-side code to work, the client’s internet browser must support these languages. There are many advantages to client-side scripting including faster response times, a more interactive application, and less overhead on the web server. Client-side code is ideal for when the page elements need to be changed without the need to contact the database. A good example would be to dynamically show and hide elements based on user inputs. One of the most common examples is input validation and Microsoft’s Visual Studio includes a set of client-side validation controls. However, disadvantages of client-side scripting are that scripting languages require more time and effort, while the client’s browser must support that scripting language. Client-side Environment The client-side environment used to run scripts is usually a browser. The processing takes place on the end users computer. The source code is transferred from the web server to the users computer over the internet and run directly in the browser. The scripting language needs to be enabled on the client computer. Sometimes if a user is conscious of security risks they may switch the scripting facility off. When this is the case a message usually pops up to alert the user when script is attempting to run. Server-side Environment The server-side environment that runs a scripting language is a web server. A user's request is fulfilled by running a script directly on the web server to generate dynamic HTML pages. This HTML is then sent to the client browser. It is usually used to provide interactive web sites that interface to databases or other data stores on the server.
  20. 20. This is different from client-side scripting where scripts are run by the viewing web browser, usually in JavaScript. The primary advantage to server-side scripting is the ability to highly customize the response based on the user's requirements, access rights, or queries into data stores. WWW Stands for "World Wide Web." It is important to know that this is not a synonym for the Internet. The World Wide Web, or just "the Web," as ordinary people call it, is a subset of the Internet. The Web consists of pages that can be accessed using a Web browser. The Internet is the actual network of networks where all the information resides. Things like Telnet, FTP, Internet gaming, Internet Relay Chat (IRC), and e-mail are all part of the Internet, but are not part of the World Wide Web. The Hyper-Text Transfer Protocol (HTTP) is the method used to transfer Web pages to your computer. With hypertext, a word or phrase can contain a link to another Web site. All Web pages are written in the hyper-text markup language (HTML), which works in conjunction with HTTP. A technical definition of the World Wide Web is: all the resources and users on the Internet that are using the Hypertext Transfer Protocol (HTTP). A broader definition comes from the organization that Web inventor Tim Berners-Lee helped found, the World Wide Web Consortium (W3C): "The World Wide Web is the universe of network-accessible information, an embodiment of human knowledge." The term WWW refers to the World Wide Web or simply the Web. The World Wide Web consists of all the public Web sites connected to the Internet worldwide, including the client devices (such as computers and cell phones) that access Web content. The WWW is just one of many applications of the Internet and computer networks. The World Web is based on these technologies: HTML - Hypertext Markup Language HTTP - Hypertext Transfer Protocol Web servers and Web browsers Here are some of the components that hold a website together:  Front End Elements. People often describe the website as having a front end and back end. In this analogy, front end is what you see, back end is what you don’t. Simple enough, except that you can’t really see the navigation structure, not all at once. But it’s a place to start. Good front-end components include the following:  The navigation structure. This is not the same as the sitemap, though that might represent it. The navigation structure is the order of the pages, the collection of what links to what. Usually it is held together by at least one navigation menu.  The page layout. This is the way things appear on the page. Is the navigation menu on the top or along the side? Are there images above the text area? Tables? Good layout is as important as any other element of design. Bad layout makes a website look crowded and slapdash. Good layout allows the eye to find what it seeks easily.  Logo. A good website has a unifying graphic around which it is built. The graphic represents your company, your organization. It often sets up the color scheme and the style elements used throughout. The logo ties the website to everything else your company does, though the printed materials, signs, whatever.
  21. 21.  Images. Photos, graphics, navigation bars, lines and flourishes, animations can all be placed on a website to bring it to life. Or, in some cases, bury it.  Contents. Few websites exist just to be looked at. The internet began as a method of sharing information. As it evolved into the World Wide Web, it became rich in all kind of media. But it still exists primarily to communicate. Well written internet-ready text is a special kind of text. Usually the information is broken into readable chunks. It is formatted to be easily scanned, and it is often optimized for search engines as well as human eyes.  Graphic Design. Many of the elements described, such as the logo, the navigation menus, the layout, images, etc., fall under the general category of graphic design. But graphic design is more than the sum of these parts. It is the overall look and feel the website will have as a result of proper use and integration of all these elements. A website with bad graphic design is usually obvious to everyone except the person who put it together. But doing graphic design well takes a special combination of talent, skill, and education.  Back End elements. Some websites are entirely static. They are the same every time you visit. You never give them information, there are no polls, bulletin boards, or referral forms. If you want to find something on the website, there is no search box, you just look around until you find it. But such sites are growing more rare as the internet becomes an ever greater part of people’s lives. Modern sites are searchable. They offer new images on each visit. They allow the user to request more information, or to post their own thoughts. Many can be updated directly from a simple panel or word-processing program. A lot of websites are datadriven, meaning that web pages are actually created on the fly, in response to the specific needs of the user. All of these functional elements are called back-end elements. In some cases there are many different ways to do the same thing. So the line between elements is often blurry.  Content Management System. This is the ability to update your website without having to directly edit the html. A robust content management system allows for documents to be prepared, edited, approved, and tracked prior to publication. Simple systems create areas on a web page that can be easily changed on a regular basis.  E-Commerce. Purchasing items from the internet has begun more and more common. The internet allows small merchants to reach a world-wide audience, while other retailers are able to maintain huge inventories of immense variety. New levels of convenience are possible, such as mail-order rentals of DVDs and games. The simple ability to safely process credit-card transactions over the internet is where this process begins.  Shopping Cart. If you have one or two products, it’s fine if visitors click a couple times, fill out information, and purchase the product. If you have a lot of different things for sale, you need a shopping cart. This is just a way for visitors to pick out different items and make a single purchase at the end of the process.  Site Search. Among all the information on the Web, somebody found yours with a simple search and a couple clicks. Do you want them to slow down and plow through pages and pages of text to find that thing they are looking for? Only if you want to lose nine out of ten visitors.  Blog feature. Blogs are much in the news these days. Blogs can be done independently, or as part of your website. Some content management systems have blog modules. Specialized blogging software can be installed on your server, or you can use blogging services.  Image-rotation. Presenting new images each time someone visits your page gives it a sense of life. Photos can be rotated, as can pieces of text, such as quotes or service descriptions.  Chatroom. There are a number of ways to allow people to interact online. A bulletin board allows people to post up messages on a topic. Chatroom allows users to comment back and forth in real time.  Contact forms. Most websites need some kind of contact form. Even if you are just giving information away, you still might want people to thank you for it. More likely you want some ongoing relationship to spring from visits to the website. Whether the goal is commerce or political organizing, contact forms are a starting point for interaction.  Referral forms. Viral marketing takes many forms. If someone likes your site, and has an easy, one-push way to notify her friends, you’ve turned your visitors into salespeople.  Newsletter registration. If you have the kind of content that is updated periodically, there are few better ways to build a regular readership than newsletters. Newsletters keep you in front of potential clients, as well as keeping your current clients in the loop about your new products, services, or campaigns. The fastest way to build a legitimate newsletter mailing list is to allow people to opt in at your website.
  22. 22.  Online databases. Databases allow us to store, sort, search through, and display large amounts of information. Online databases bring this technology seamlessly to the Web.  Password protected sections. The public area of your website is a great way to serve a variety of audiences. But what if you have a membership that deserves better, more comprehensive content? Or what if you want certain registered visitors to be able to perform online actions? You may have a section of your website set aside for your own internal processes. This is easily done by creating password protected sections.  Downloadable files. From simple flyers to hundred page documents, e-books, music files, and even movie clips can be downloaded from websites. This is an easy way to distribute files all over the world.  Multi-media. Some websites call for more than just text and images. Photo-tours, video-clips, sound-clips all can add to the experience if they are well matched to the type of site and profile of the target audience.  Security. All kinds of information can be found hidden on websites. Trade secrets, proprietary programming, client credit card numbers, and every imaginable piece of personal data. Press releases have been uncovered early, strictly internal memos have been leaked, all because the internet has many ways of exposing data. If you are passing information online that is not meant for everyone, then you want to ensure you have the right level of security. Other components. Some elements that are essential to a website aren’t properly described as either front-end or backend components. Still, a website doesn’t work right without them.  Hosting. Hosting is where your website is physically located. On a server, somewhere, are a set of files that are transmitted to user computers when they call your name.  Domain Name. This is the address. When someone asks to see your website, they put this address into the internet, and your site is served up to them.  Online Promotion. Not exactly part of the website, but often part of the design as well as the activity surrounding its launch is the online promotion. A site with no visitors is like a huge monument built in an uninhabited desert. What is the difference between a portal and a website? A website is a unique location which is specified by a URL. It contains many pages, domains and sub domains. A web portal is the entrance (gate) to the Web. One can enter the web from many different portals (gates) and either dive into the portal inner web or move to other portals in the web. Yahoo is an good example for web portal. A Webportal is also a type of website but it differs in content and services from a typical website that provides only specialized information • A Webportal is a launch pad to a host of web based services such as email, shopping, gaming, news, weather and so on whereas a website is concerned with providing information about a company only. We have often heard the term portal and website. Both of them are sometimes used interchangeably. However there is a difference between the two. Let’s find out all about portals and websites. Usually a portal is used to describe a website that acts as an entry point or gateway to an array of services. It is obvious that all sites do this to a certain degree but a portal has a wide range of resources including search facility, directory of other sites, news,
  23. 23. e-mail and lot more. For instance, Yahoo is a great example of a general portal. There can be industry specific or occupation specific portals. Also, many people refer to a portal to as a form of content management system such as PhpNuke. A website is a collection of related web pages containing images, videos or other digital assets. It is hosted on at least one web server, accessible via a network such as the Internet or a private local area network through an Internet address known as a Uniform Resource Locator. All publicly accessible websites collectively constitute the World Wide Web. A web page is a document, typically written in plain text interspersed with formatting instructions of Hypertext Markup Language (HTML, XHTML). The page may incorporate elements from other websites with suitable markup anchors. We can also say that a website is an application deployed to a web server. A Servlet/JSP application has some level of interaction with the client that makes the experience interactive. A portal on the other hand builds heavily upon the dynamic nature of a normal website. Also, a portal has built in user functions and a fantastic ability for users to customize their own experience. A portal finds the information for the user whereas on a website the user has to search for it. A portal displays all the content in one place while information is usually dispersed across a website. A portal uses a consistent framework for presenting the information in a standard way. The services available through the portal are all designed to fit within a standard portal framework. This consistency makes it easier to learn and use these services. On the other hand, there is a learning curve for users of typical website to get familiar with all the browsing capabilities. The information presented in a typical web site is usually general and intended for a wider audience. Thus a portal is a complete environment for managing and integrating a large number of diverse applications and user repositories across an enterprise wide system. A single administrative interface makes it possible to manage users, applications, content, look, feel and navigation of an entire website. Centralized administration of a huge web based infrastructure is probably the most compelling reason for adopting the portal.