1) INTRODUCTION OF ASP.NET & ITS ADVANTAGES:-

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1 1) INTRODUCTION OF ASP.NET & ITS ADVANTAGES:- INTRODUCTION OF ASP.NET:- ASP.NET is a web development platform, which provides a programming model, a comprehensive software infrastructure and various services required to build up robust web applications for PC, as well as mobile devices. ASP.NET works on top of the HTTP protocol, and uses the HTTP commands and policies to set a browser-to-server bilateral communication and cooperation. ASP.NET is a part of Microsoft.Net platform. ASP.NET applications are compiled codes, written using the extensible and reusable components or objects present in.net framework. These codes can use the entire hierarchy of classes in.net framework. Advantages ASP.NET:- 1) ASP.NET significantly reduces the amount of code required for building large and complex applications which can increase overall development speed and reduce development costs. 2) Just-in-time compilation, smart caching technologies and native optimization dramatically increase overall application performance. 3) ASP.NET Framework supports varied languages, it allows you to select the language that better applies to your application. 4) ASP.NET provides ability of cross platform migration. 5) ASP.NET provides simplicity making it easy to perform common tasks including configuration and deployment. 6) ASP.NET features vast class library enclosing a large number of common functions and ready-touse custom web-controls that allow creating professional applications with no need to develop from scratch. 7) ASP.NET ensured high reliability and security due to built-in Windows authentication and perapplication configuration. 8) ASP.NET is regularly updated by Microsoft to meet the most up-to-date technology requirements 2) ASP.NET Life Cycle:- The ASP.NET life cycle could be divided into two groups: 1 Application Life Cycle Page Life Cycle ASP.NET Application Life Cycle The application life cycle has the following stages: User makes a request for accessing application resource, a page. Browser sends this request to the web server. A unified pipeline receives the first request and the following events take place: o An object of the class ApplicationManager is created. o An object of the class HostingEnvironment is created to provide information regarding the resources. o Top level items in the application are compiled.

2 2 Response objects are created. The application objects such as HttpContext, HttpRequest and HttpResponse are created and initialized. An instance of the HttpApplication object is created and assigned to the request. The request is processed by the HttpApplication class. Different events are raised by this class for processing the request. ASP.NET Page Life Cycle When a page is requested, it is loaded into the server memory, processed, and sent to the browser. Then it is unloaded from the memory. At each of these steps, methods and events are available, which could be overridden according to the need of the application. In other words, you can write your own code to override the default code. The Page class creates a hierarchical tree of all the controls on the page. All the components on the page, except the directives, are part of this control tree. You can see the control tree by adding trace= "true" to the page directive. We will cover page directives and tracing under 'directives' and 'event handling'. The page life cycle phases are: Initialization Instantiation of the controls on the page Restoration and maintenance of the state Execution of the event handler codes Page rendering Understanding the page cycle helps in writing codes for making some specific thing happen at any stage of the page life cycle. It also helps in writing custom controls and initializing them at right time, populate their properties with view-state data and run control behavior code. Following are the different stages of an ASP.NET page: Page request - When ASP.NET gets a page request, it decides whether to parse and compile the page, or there would be a cached version of the page; accordingly the response is sent. Starting of page life cycle - At this stage, the Request and Response objects are set. If the request is an old request or post back, the IsPostBack property of the page is set to true. The UICulture property of the page is also set. Page initialization - At this stage, the controls on the page are assigned unique ID by setting the UniqueID property and the themes are applied. For a new request, postback data is loaded and the control properties are restored to the view-state values. Page load - At this stage, control properties are set using the view state and control state values. Validation - Validate method of the validation control is called and on its successful execution, the IsValid property of the page is set to true. Postback event handling - If the request is a postback (old request), the related event handler is invoked.

3 3 Page rendering - At this stage, view state for the page and all controls are saved. The page calls the Render method for each control and the output of rendering is written to the OutputStream class of the Response property of page. Unload - The rendered page is sent to the client and page properties, such as Response and Request, are unloaded and all cleanup done. 3) Net Framework ARCHITECTURE:- Before going to the next session on Visual Studio.Net, let us go through at the various components of the.net framework 3.5. The following table describes the components of the.net framework 3.5 and the job they perform: Components & FEATURES OF.NET FRAMEWORK (1) Common Language Runtime or CLR:- It performs memory management, exception handling, debugging, security checking, thread execution, code execution, code safety, verification, and compilation. The code that is directly managed by the CLR is called the managed code. When the managed code is compiled, the compiler converts the source code into a CPU independent intermediate language (IL) code. A Just In Time(JIT) compiler compiles the IL code into native code, which is CPU specific. (2).Net Framework Class Library:- It contains a huge library of reusable types. classes, interfaces, structures, and enumerated values, which are collectively called types. (3) Common Language Specification:- It contains the specifications for the.net supported languages and implementation of language integration. (4) Common Type System:- It provides guidelines for declaring, using, and managing types at runtime, and cross-language communication. (5) Metadata and Assemblies:- Metadata is the binary information describing the program, which is either stored in a portable executable file (PE) or in the memory. Assembly is a logical unit consisting of the assembly manifest, type metadata, IL code, and a set of resources like image files. (6) Windows Forms:- Windows Forms contain the graphical representation of any window displayed in the application. (7) ASP.NET and ASP.NET AJAX:- ASP.NET is the web development model and AJAX is an extension of ASP.NET for developing and implementing AJAX functionality. ASP.NET AJAX contains the components that allow the developer to update data on a website without a complete reload of

4 4 the page. (8) ADO.NET:- It is the technology used for working with data and databases. It provides access to data sources like SQL server, OLE DB, XML etc. The ADO.NET allows connection to data sources for retrieving, manipulating, and updating data. (9) Windows Workflow Foundation (WF)::- It helps in building workflow-based applications in Windows. It contains activities, workflow runtime, workflow designer, and a rules engine. (10) Windows Presentation Foundation:- It provides a separation between the user interface and the business logic. It helps in developing visually stunning interfaces using documents, media, two and three dimensional graphics, animations, and more. (11) Windows Communication Foundation (WCF):- It is the technology used for building and executing connected systems. (12) Windows CardSpace:- It provides safety for accessing resources and sharing personal information on the internet. (13) LINQ:- It imparts data querying capabilities to.net languages using a syntax which is similar to the tradition query language SQL. 4) Architecture of CLR:- FEATURES OF CLR:-

5 5 Automatic lifetime management Garbage collection for all.net objects, Multi-generational mark-and-compact garbage collection (GC) No stray pointers, no circular references Self-configuration, dynamic tuning Exception handling, Error handling as a first-class concept (not Boolean or HRESULTs), Dramatically improved error reporting Windows Language SEH integration Several compilation models: Native (for example, Managed C++) and Microsoft Intermediate Language (MSIL or IL) (for example, VB and C#) Lack of an interpreter as the code compiles at install-time or runtime Code correctness and type safety, Verifiable IL that guarantees type safety No unsafe casts, no uninitialized variables, no out-of-bounds array indexing Evidence-based security, Both code- and user-based security Extensible permissions 4) ASP.NET Authentication & Authorization & its types? Authentication :- Authentication is the process of verifying the identity of a user by obtaining some sort of credentials and using those credentials to verify the user's identity. If the credentials are valid, the authorization process starts. Authentication process always proceeds to Authorization process. ASP.Net Authentication The ASP.NET authentication scheme that is used to identify users who view an ASP.NET application. An ASP.net application has two separate authentication levels because all requests coming through IIS before it handled by ASP.NET. After IIS authentication schemes ASP.NET implements additional authentication schemes. They are : Windows Authentication :- Windows Authentication provider is the default authentication provider for ASP.NET applications. When a user using this authentication logs in to an application, the credentials are matched with the Windows domain through IIS. There are 4 types of Windows Authentication methods: 1) Anonymous Authentication - IIS allows any user 2) Basic Authentication - A windows username and password has to be sent across the network (in plain text format, hence not very secure). 3) Digest Authentication - Same as Basic Authentication, but the credentials are encrypted. Works only on IE 5 or above 4) Integrated Windows Authentication - Relies on Kerberos technology, with strong credential encryption Forms Authentication :- This authentication relies on code written by a developer, where credentials are matched against a database. Credentials are entered on web forms, and are matched with the database table that contains the user information

6 6 Authorization:- Authorization is the process of allowing an authenticated users to access the resources by checking whether the user has access rights to the system. Authorization helps you to control access rights by granting or denying specific permissions to an authenticated user. Asp.Net Authorization:- ASP.NET allows two ways to authorize access to a given resources, they are URL authorization and File authorization. URL authorization :- URL authorization maps users and roles to URLs in ASP.NET applications File authorization :- File authorization validate the ACL (access control list) of the.aspx or.asmx handler file to determine whether a user should have access to the file. 5) Explain the ASP.NET validation & its types? Ans:- Validations can be performed on the server side or on the client side ( web browser). The user input validation take place on the Server Side during a post back session is called Server Side Validation and the user input validation take place on the Client Side (web browser) is called Client Side Validation. Client Side Validation does not require a postback. If the user request requires server resources to validate the user input, you should use Server Side Validation. If the user request does not require any server resources to validate the input, you can use Client Side Validation. Server Side Validation In the Server Side Validation, the input submitted by the user is being sent to the server and validated using one of server side scripting languages such as ASP.Net, PHP etc. After the validation process on the Server Side, the feedback is sent back to the client by a new dynamically generated web page. It is better to validate user input on Server Side because you can protect against the malicious users, who can easily bypass your Client Side scripting language and submit dangerous input to the server. Client Side Validation In the Client Side Validation you can provide a better user experience by responding quickly at the browser level. When you perform a Client Side Validation, all the user inputs validated in the user's browser itself. Client Side validation does not require a round trip to the server, so the network traffic which will help your server perform better. This type of validation is done on the browser side using script languages such as JavaScript, VBScript or HTML5 attributes. For example, if the user enter an invalid format, you can show an error messeage immediately before the user move to the next field, so the user can correct every field before they submit the form. Mostly the Client Side Validation depends on the JavaScript Language, so if users turn JavaScript off, it can easilly bypass and submit dangerous input to the server. So the Client Side Validation can not protect your application from malicious attacks on your server resources and databases. As both the validation methods have their own significances, it is recommended that the Server side validation is more SECURE

7 7 6) EXPLAIN HTML controls & Its advantages? HTML controls :- HTML controls are the native browser elements and they are part of HTML language. These are client side controls which is accessible only in the HTML page, so it will improve the performance of the web page. HTML controls on an ASP.NET Web page are not available to the web server. Advantages of HtmlControls * HtmlControls are very useful if you need to translate classic ASP web site to ASP.NET. Just add runat="server" to needed <input> or <select > tags and you can convert HTML form to ASP.NET web form fast. * With HtmlControls you can easily access any html tag on web page. For example, if you want to change some attribute of <body> tag, just add runat="server" and you can do it with one line of code like with TextArea in last example. * If you need to manipulate HTML tags, you will can do it easily with HtmlControls, instead of working with ASP.NET code inside of <% and %> like in classic ASP before. * Reset of all input elements on form is very easy to do with HtmlInputReset control. * Adding meta tags is easy to do with HtmlMeta control. Or, simply add id and runat="server" to meta tag. 7) Explain the html server controls & web server controls? HTML Server controls :- You can add the attribute runat="server" to any HTML control, such cases it will be an HTML server control. These controls map directly to html tags and without runat="server" it cannot access the control in code behind. Web Server Controls or ASP.NET controls :- Web Server Controls are group of controls derived directly from the System.Web.UI.WebControls base class. They are executed on the server side and output HTML sent back to the client browser. These controls are programmable and reusable that can perform function as the ordinary HTML controls. Web Server Controls can detect the target browser's capabilities and render themselves accordingly. 8. What is the difference between client side and server side programming? Server side programming: - The combination of hardware and software that outputs documents (web pages) when requested by a client Server side programing interacts with the server, and outputs documents (web pages). ASP (Active Server Pages), cgi/perl, Cold Fusion, PHP, and SSI (Server Side Includes) are server side languages.

8 8 Since all server side programing is done BEFORE the page is sent to the client, NONE of the code has to be downloaded and the code can't be seen when viewing the source code of a document. All server side programing IS server dependent (it must interact with the server) so it can only be viewed when loaded through the server. (If viewed from a floppy or hard disk, no scripting (parsed) output will be displayed.) Server side programming IS NOT client dependant, so web pages functionality will be the same, regardless of what client (browser) is used. (Note - client side scripting such as JavaScript or HTML 4 can be sent to the browser as parsed output, and will therefore be browser dependant.) Client side programing - The application (Netscape or Internet Explorer) that the end user (web surfer) uses to view documents (web pages). Client side programing interacts with the client (Netscape or Internet Explorer) to show the document. HTML and JavaScript are client side languages. All client side programing code must be downloaded to the browser and much of the code can be viewed when viewing the source code of a document. Client side programming IS NOT server dependant, so web pages will function the same way, when opened from the web, a floppy disk, or your hard drive. Client side programming IS client dependant, so web pages will function differently in different clients. Javascript and HTML 4 work in version 4 browsers, but not version 2 browsers. 9) ASP.NET Validators ASP.NET validation controls validate the user input data to ensure that useless, unauthenticated, or contradictory data don't get stored. ASP.NET provides the following validation controls: RequiredFieldValidator :- The RequiredFieldValidator control ensures that the required field is not empty. It is generally tied to a text box to force input into the text box. RangeValidator:- The RangeValidator control verifies that the input value falls within a predetermined range. CompareValidator:- The CompareValidator control compares a value in one control with a fixed value or a value in another control. RegularExpressionValidator:- The RegularExpressionValidator allows validating the input text by matching against a pattern of a regular expression. The regular expression is set in the ValidationExpression property. CustomValidator:- The CustomValidator control allows writing application specific custom validation routines for both the client side and the server side validation. The client side validation is accomplished through the ClientValidationFunction property. The client side validation routine should be written in a scripting language, such as JavaScript or VBScript, which the browser can understand. The server side validation routine must be called from the control's ServerValidate event handler. The server side validation routine should be written in any.net language, like C# or VB.Net.

9 9 ValidationSummary:- The ValidationSummary control does not perform any validation but shows a summary of all errors in the page. The summary displays the values of the ErrorMessage property of all validation controls that failed validation. The following two mutually inclusive properties list out the error message: ShowSummary : shows the error messages in specified format. ShowMessageBox : shows the error messages in a separate window. 10) EXPLAIN ADO.NET ACHITECTURE ADO.NET ACHITECTURE:- ADO.NET provides a bridge between the front end controls and the back end database. The ADO.NET objects encapsulate all the data access operations and the controls interact with these objects to display data, thus hiding the details of movement of data. The following figure shows the ADO.NET objects at a glance: The DataSet Class:- The dataset represents a subset of the database. It does not have a continuous connection to the database. To update the database a reconnection is required. The DataSet contains DataTable objects and DataRelation objects. The DataRelation objects represent the relationship between two tables. The DataTable Class:- The DataTable class represents the tables in the database. It has the following important properties; most of these properties are read only properties except the PrimaryKey property: The DataRow Class:- The DataRow object represents a row in a table. The DataAdapter Object:- The DataAdapter object acts as a mediator between the DataSet object and the database. This helps the Dataset to contain data from multiple databases or other data source. The DataReader Object:- The DataReader object is an alternative to the DataSet and DataAdapter combination. This object provides a connection oriented access to the data records in the database. These objects are suitable for read-only access, such as populating a list and then breaking the connection.

10 10 DbCommand and DbConnection Objects:- The DbConnection object represents a connection to the data source. The connection could be shared among different command objects. The DbCommand object represents the command or a stored procedure sent to the database from retrieving or manipulating data. 11) HOW TO ACCESS A DATABASE WITH USING ADO.NET? ASP.NET allows the following sources of data to be accessed and used: Databases (e.g., Access, SQL Server, Oracle, MySQL) XML documents Business Objects Flat files ASP.NET hides the complex processes of data access and provides much higher level of classes and objects through which data is accessed easily. These classes hide all complex coding for connection, data retrieving, data querying, and data manipulation. (1) Create a web site and add a SqlDataSourceControl on the web form (2) Click on the Configure Data Source option. (3) Click on the New Connection button to establish connection with a database (4) Once the connection is set up, you may save it for further use. At the next step, you are asked to configure the select statement (5) Select the columns and click next to complete the steps. Observe the WHERE, ORDER BY, and the Advanced buttons. These buttons allow you to provide the where clause, order by clause, and specify the insert, update, and delete commands of SQL respectively. This way, you can manipulate the data. (6) Add a GridView control on the form. Choose the data source and format the control using AutoFormat option. (7) After this the formatted GridView control displays the column headings, and the application is ready to execute. (8) Finally execute the application. 12) EXPLAIN ASP.NET - Error Handling: Error handling in ASP.NET has three aspects: Tracing - tracing the program execution at page level or application level. Error handling - handling standard errors or custom errors at page level or application level. Debugging - stepping through the program, setting break points to analyze the code It has a label control, a dropdown list, and a link. The dropdown list loads an array list of famous quotes and the selected quote is shown in the label below. It also has a hyperlink which has points to a nonexistent link.

11 11 Tracing:-To enable page level tracing, you need to modify the Page directive and add a Trace attribute. It provides the following information at the top: Session ID Status Code Time of Request Type of Request Request and Response Encoding The status code sent from the server, each time the page is requested shows the name and time of error if any. Error Handling Although ASP.NET can detect all runtime errors, still some subtle errors may still be there. Observing the errors by tracing is meant for the developers, not for the users. Hence, to intercept such occurrence, you can add error handing settings in the web.config file of the application. It is application-wide error handling. For example, you can add the following lines in the web.config file The <customerrors> section has the possible attributes: Mode : It enables or disables custom error pages. It has the three possible values: o o o On : displays the custom pages. Off : displays ASP.NET error pages (yellow pages) remoteonly : It displays custom errors to client, display ASP.NET errors locally. defaultredirect : It contains the URL of the page to be displayed in case of unhandled errors. To put different custom error pages for different type of errors, the <error> sub tags are used, where different error pages are specified, based on the status code of the errors. 13) The Advantages of Centralized Database Storage:- Improves Data Preservation:- Centralized database storage improves data preservation. PC computers and laptops rarely offer fault tolerance -- the capacity to continue functioning after hardware failure. Fault tolerance requires duplicate components, which drives up costs. The lack of fault tolerance places any data stored only on a PC or laptop at risk for permanent loss. Centralized storage often includes a fault-tolerant setup and redundant storage that preserves the data, even in the event of a catastrophic hardware failure in a hard drive. Improves Physical Security:- Locally stored data represents an ongoing physical security risk. Laptops and notebooks get lost or stolen. An unattended PC presents an opportunity for anyone to

12 12 access, steal or damage locally stored data. Centralized database storage and proper server room security restrict direct physical access to a single location and a small group of people. Improves Data Security:- As businesses now maintain vast quantities of sensitive consumer information, data protection is a mission-critical issue. Providing data security with central database storage creates fewer challenges than ensuring data security across multiple local storage sites. Data access policies limit the damage one compromised computer can do, as does implementing encrypted virtual private networks, firewalls and rigorous password protection. Reduces costs:- Centralized storage requires the business to invest heavily in the server technology, such as fault tolerance, but also allows it to cut overall costs. The maintenance to the central server proves less costly than maintenance to multiple computers, especially if the business operates in multiple locations. Centralized storage also reduces overall space requirements for data storage and processing. Improved Reliability and Update Speed:- Centralized storage typically employs higher-quality components and redundancy, which makes it significantly more reliable than local storage. Centralized database storage facilitates virtualization and provides comprehensive data access, if desired, from anywhere in the world. Updates carried out on a database run on centralized storage carry through to all end-users, as opposed to local storage, which only applies to that computer. 14) EXPLAIN XML Web services? XML stands for Extensible Markup Language and is a text-based markup language derived from Standard Generalized Markup Language (SGML). This tutorial will teach you basics of XML. The tutorial is divided into sections such as XML Basics, Advanced XML and XML tools. Each of these sections contain related topics with simple and useful examples. XML Web services and XML Web service clients should now be created using Windows Communication Foundation. Building a simple Web service using ASP.NET is relatively easy and is covered in ASP.NET XML Web Service Basics and Walkthrough: Building a Basic XML Web Service Using ASP.NET. However, the true power of Web services is realized when you look at the infrastructure. Web services are built on top of the.net Framework and the common language runtime. A Web service can take advantage of these technologies. For instance, the performance, state management, and authentication supported by ASP.NET can all be taken advantage of by building Web services using ASP.NET. The infrastructure for Web services is built to conform to industry standards such as SOAP, XML, and WSDL, and this allows clients from other platforms to interoperate with Web services. As long as a client can send standards-compliant SOAP messages, formatted according to a service description, that client can call a Web service created using ASP.NET (regardless of the platform on which the client resides). For

13 more information on how ASP.NET provides an attribute-based mechanism for modifying the format of the expected SOAP, see Customizing SOAP Message Formatting. When you build a Web service using ASP.NET, it automatically supports clients communicating using the SOAP, HTTP-GET, and HTTP-POST protocols. Since HTTP-GET and HTTP-POST support passing messages in URL-encoded name-value pairs, the data type support for these two protocols is not as rich as that supported for SOAP. In SOAP, which passes data to and from the Web service using XML, you can define complex data types using XSD schemas, which support a richer set of data types. Developers building a Web service using ASP.NET do not have to explicitly define complex data types they expect using an XSD schema. Rather, they can simply build a managed class. ASP.NET handles mapping class definitions to an XSD schema and mapping object instances to XML data in order to pass it back and forth across a network. It is important to note that Web services are not a replacement for DCOM, but rather a messaging infrastructure for communicating across platforms using industry standards ) EXPLAIN IIS - Internet Information Server Ans:- Internet Information Server :- Internet Information Server (IIS) is one of the most popular web servers from Microsoft that is used to host and provide Internet-based services to ASP.NET and ASP Web applications. A web server is responsible for providing a response to requests that come from users. When a request comes from client to server IIS takes that request from users and process it and send response back to users. Internet Information Server (IIS) has it's own ASP.NET Process Engine to handle the ASP.NET request. The way you configure an ASP.NET application depends on what version of IIS the application is running on. Internet Information Server (IIS) includes a set of programs for building and administering Web applications, search engines, and support for writing Web-based applications that access databases such as SQL Server. With IIS, you can make your computer to work as a Web server and provides the functionality to develop and deploy ASP.NET Web applications on the server. You can also set security for a particular Website for specific Users and Computer in order to protect it from unauthorized access. IIS helps organizations to increase Web sites and application availability while lowering system administration and cost of deployment. IIS 7.5 supports HTTP, HTTPS, FTP, FTPS, SMTP and NNTP. 16) EXPLAIN ASP.NET Debugging Debugging allows the developers to see how the code works in a step-by-step manner, how the values of the variables change, how the objects are created and destroyed, etc.

14 14 When the site is executed for the first time, Visual Studio displays a prompt asking whether it should be enabled for debugging: Breakpoints:- Breakpoints specifies the runtime to run a specific line of code and then stop execution so that the code could be examined and perform various debugging jobs such as, changing the value of the variables, step through the codes, moving in and out of functions and methods etc. 17) EXPLAIN & ITS TYPES Electronic mail is a method of exchanging digital messages from an author to one or more recipients. Modern operates across the Internet or other computer networks. Some early systems required the author and the recipient to both be online at the same time, in common with instant messaging. Today's systems are based on a store-and-forward model. servers accept, forward, deliver, and store messages. THERE ARE THREE DIFFERENT TYPES OF S:- 1. MARKETING S:- Marketing (or Bulk) s stimulate your clients and leads. They contain informative / incentive messages. The recipient must agree to receive such s: opt-in is mandatory. There can be a periodicity, but the message can also be sent to a segment in particular. Nonetheless, the main point is that messages are sent independently from specific actions from the clients. 2. Notification s:- Notification are also known as trigger, alert or auto-responder. They allow the user to be notified each time a particular event happens (or has happened). More generally, the notification may be used in order to celebrate and/or mark an event. It is either the recipients themselves, or the sender that will establish criteria for an outgoing message to be triggered by an event. 3. Transactional s:- This is an expected message and its content is information that the client wishes to check or confirm, and not "discover". This type of is not intended to optimize the customer relationship but to define it and mark it out. It is a point of reference in one s CRM. 18) WEB SERVER? POP :- POP, or Post Office Protocol, is a way of retrieving information that dates back to a very different Internet than we use today. Computers only had limited, low bandwidth access to remote computers, so engineers created POP in an effort to create a dead simple way to download copies of s for offline reading, then remove those mails from the remote server. POP3 is the current version of this particular style of protocol, and still remains one of the most popular. Since POP3 creates local copies of s and deletes the originals from the server, the s are tied to that specific machine, and cannot be accessed via any webmail or any separate client on other computers. At least, not without doing a lot of forwarding or porting around mailbox files.

15 15 IMAP:- IMAP was created in 1986, but seems to suit the modern day world of omnipresent, always-on Internet connectivity quite well. The idea was keep users from having to be tied to a single client, giving them the ability to read their s as if they were in the cloud. Compared to POP3, IMAP allows users to log into many different clients or webmail interfaces and view the same s, because the s are kept on remote servers until the user deletes them. In a world where we now check our on web interfaces, clients, and on mobile phones, IMAP has become extremely popular. It isn t without its problems, though. Because IMAP stores s on a remote mail server, you ll have a limited mailbox size depending on the settings provided by the service. If you have huge numbers of s you want to keep, you could run into problems sending and receiving mail when your box is full. Some users sidestep this problem by making local archived copies of s using their client, and then deleting them from the remote server. SMTP:- Simple Mail TransferProtocol, a protocol for sending messages between servers. Most e- mail systems that send mail over the Internet use SMTP to send messages from one server to another; the messages can then be retrieved with an client using eitherpop or IMAP. In addition, SMTP is generally used to send messages from a mail client to a mail server. This is why you need to specify both the POP or IMAP server and the SMTP server when you configure your application. SMTP is part of the application layer of the TCP/IP protocol. Using a process called "store and forward," SMTP moves your on and across networks. It works closely with something called the Mail Transfer Agent (MTA) to send your communication to the right computer and inbox. MAPI:- MAPI (Messaging Application Program Interface) is a Microsoft Windows program interface that enables you to send from within a Windows application and attach the document you are working on to the note. Applications that take advantage of MAPI include word processors, spreadsheets, and graphics applications. MAPI-compatible applications typically include a Send Mail or Send in the File pulldown menu of the application. Selecting one of these sends a request to a MAPI server. 19) ADVANTAGES OF S:- s are easy to use. You can organize your daily correspondence, send and receive electronic messages and save them on computers. s are fast. They are delivered at once around the world. No other form of written communication is as fast as an . The language used in s is simple and informal. When you reply to an you can attach the original message so that when you answer the recipient knows what you are talking about. This is important if you get hundreds of s a day. It is possible to send automated s with a certain text. In such a way it is possible to tell the sender that you are on vacation. These s are called auto responders.

16 16 s do not use paper. They are environment friendly and save a lot of trees from being cut down. s can also have pictures in them. You can send birthday cards or newsletters as s. Products can be advertised with s. Companies can reach a lot of people and inform them in a short time. Disadvantages of s s may carry viruses. These are small programs that harm your computer system. They can read out your address book and send themselves to a number of people around the world. Many people send unwanted s to others. These are called spam mails. It takes a lot of time to filter out the unwanted s from those that are really important. s cannot really be used for official business documents. They may be lost and you cannot sign them. Your mailbox may get flooded with s after a certain time so you have to empty it from time to time.