What is a Web application ?and How does it runs on server?

A web-based application is any application that uses a web browser as a client. The term may also mean a computer software application that is coded in a browser-supported programming language (such as JavaScript, combined with a browser-rendered markup language like HTML) and reliant on a common web browser to render the application executable.

OR

A web application is a collection of static and dynamic web pages. A static web page is one that does not change when a user requests it: the web server sends the page to the requesting web browser without modifying it.

Flow of a web application is starts with these following steps:

•   Initial request is triggered by user through the browser over the internet to the web server
• The web server manages the request(s) forwarding to the applicable web application server
• The web application server(s) performs the requested task
• Access the database
• Response back to the web server
• The web server responds back to user with the successful transaction
• Information appears on the user’s monitor.

 These are the following business advantages: 

1.Cost effective development:

With web-based applications, users access the system via a uniform environment—the web browser. While the user interaction with the application needs to be thoroughly tested on different web browsers, the application itself needs only be developed for a single operating system. There’s no need to develop and test it on all possible operating system versions and configurations. This makes development and troubleshooting much easier.

2.Accessible anywhere:

Unlike traditional applications, web systems are accessible anytime, anywhere, via a PC with an Internet connection, putting the user in charge of where and when they access the application.

3.Easily customization:

The user interface of web-based applications is easier to customize than it is in desktop applications. This makes it easier to update the look and feel of the application, or to customize the presentation of information to different user groups.

4.Accessible for a range of devices:

In addition to customizing content for user groups, content can also be customized for presentation on any device connected to the internet, including PDAs, mobile phones, etc., further extending the user’s ability to receive and interact with information.

5.Improved Interoperability:

Using internet technologies based on industry-wide standards, it’s possible to achieve a far greater level of interoperability between applications than with isolated desktop systems. For example, it is much easier to integrate a web-based shopping cart system with a web-based accounting package than it is to get two proprietary systems to talk to each other. Web-based architecture makes it possible to rapidly integrate enterprise systems, improving work-flow and other business processes.

6.Easier installation and maintenance:

Installation and maintenance becomes less complicated. Once a new version or upgrade is installed on the host server, all users can access it straight away. There is no need to upgrade each client PC. Rolling out new software can be accomplished more easily, requiring only that users have up-to-date browsers and plugins. And as the upgrades are only performed by an experienced professional to a single server, the results are more predictable and reliable.

7.Adaptable to increased workload:

Increasing processor capacity also becomes a far simpler operation. If an application requires more power to perform tasks, only the server hardware needs to be upgraded. The capacity of web-based software can be increased by “clustering” or running the software on several servers simultaneously. As workload increases, new servers can be added to the system easily—Google, for example, runs on thousands of inexpensive Linux servers. If a server fails, it can be replaced without affecting the overall performance of the application.

8.Security:

Web-based applications are typically deployed on dedicated servers, which are monitored and maintained by experienced server administrators. This is far more effective than monitoring hundreds or even thousands of client computers, as is the case with new desktop applications.

9.Flexible core technologies:
Any of three core technologies can be used for building web-based applications, depending on the requirements of the application.

•  JSP and Servlets(Sun microsystems). 
• Asp.Net and Sql Server(Microsoft).
•  The third option is the Open Source platform (predominantly PHP and MySQL).

Web applications commonly use a combination of server-side script (ASP, PHP, JSP, ASP.NET etc.) and client-side script (HTML, JavaScript, etc.) to develop the application. The client-side script deals with the presentation of the information while the server-side script deals with all the hard stuff like storing and retrieving the information.

 Web Application resides with web server which will located under network server. Clients are going to interact with web server via following some open standard:

1. Web Server:

A web server is software that serves files in response to requests from web browsers. A web server is sometimes called an HTTP server. Common web servers include IIS, Netscape Enterprise Server, iPlanet Web Server, and Apache Tomcat.

2. Web Browser:

It is software which resides on client system and it is responsible to make request in the form of HTTP and HTTP is the open standard protocol which is applicable for different types of or all types of users. HTTP derived from W3 ORG.

3. HTML (Hyper Text Markup Language):

HTML is a light weight language which is used for showing output in the browsers.

Using HTML, we can design the web pages that are displayed in the client browser.

Every web application must produce to output to the client in HTML form only.

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