Introduction

A web browser (commonly referred to as a browser) is a software application for retrieving, presenting, and traversing information resources on the World Wide Web. An information resource is identified by a Uniform Resource Identifier (URI/URL) and may be a web page, image, video or other piece of content.Hyperlinks present in resources enable users easily to navigate their browsers to related resources.

Although browsers are primarily intended to use the World Wide Web, they can also be used to access information provided by web servers in private networks or files in file systems.

Types of Browsers

There are five major browsers used today - Internet Explorer, Firefox, Safari, Chrome and Opera. I will give examples from the open source browsers - Firefox,Chrome and Safari, which is partly open source. According to the W3C browser statistics, currently(October 2009), the usage share of Firefox, Safari and Chrome together is nearly 60%. So nowdays open source browsers are a substantial part of the browser business.

Functionality

The browser main functionality is to present the web resource you choose, by requesting it from the server and displaying it on the browser window. The resource format is usually HTML but also PDF, image and more. The location of the resource is specified by the user using a URI (Uniform resource Identifier).

The way the browser interprets and displays HTML files is specified in the HTML and CSS specifications. These specifications are maintained by the W3C (World Wide Web Consortium) organization, which is the standards organization for the web. The current version of HTML is 4 . Version 5 is in progress. The current CSS version is 2 and version 3 is in progress.

Interface

Browsers’ user interface have a lot in common with each other. Among the common user interface elements are

Address bar for inserting the URI
Back and forward buttons
Bookmarking options
A refresh and stop buttons for refreshing and stopping the loading of current document
Home button that gets you to your home page

Component

Web browsers consist: Interface- This includes the address bar, back/forward button, bookmarking menu etc. Every part of the browser display except the main window where you see the requested page. Layout engine- Responsible for displaying the requested content. For example if the requested content is HTML, it is responsible for parsing the HTML and CSS and displaying the parsed content on the screen. Rendering engine-responsible for displaying the requested content. For example if the requested content is HTML, it is responsible for parsing the HTML and CSS and displaying the parsed content on the screen. JavaScript interpreter- Used to parse and execute the JavaScript code. UI backend- used for drawing basic widgets like combo boxes and windows. It exposes a generic interface that is not platform specific. Underneath it uses the operating system user interface methods. Networking component-used for network calls, like HTTP requests. It has platform independent interface and underneath implementations for each platform. Data persistence component- This is a persistence layer. The browser needs to save all sorts of data on the hard disk, for examples, cookies. The new HTML specification (HTML5) defines ‘web database’ which is a complete (although light) database in the browser.

References

I’m an inline-style link I’m an inline-style link I’m an inline-style link I’m an inline-style link I’m an inline-style link