Translate how browsers work

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How does a browser work.
Introduction:
Browsers can be said to be the most widely used software. In this articleArticle, I will explain how they work behind the scenes. We will see what happened when you typed 'Google. com' in the address bar to the middle of the page in the browser.

The browser we will discuss

Currently, we mainly use five types of browsers-Internet Explorer, Firefox, Safari, chorm, and opera.

I will give some examples from open source browsers-Firefox, chorm, Safari is partially open source.

AccordingW3C(World Wide Web ConsortiumBrowser statistics of the World Wide Web alliance, the current (2011Year5Month ),Firefox,SafariAndChromeThe market share is close60%. (Original:2009Year10The data has not changed much.) Therefore, it can be said that open-source browsers have occupied half of the browser market.

Main functions of the browser

The main function of the browser is to present our Web requests. It needs to request resources from the server and display them in the browser window. The resource format is usually htm, which also includes PDF, image, or other formats. The resource location is a Uniform Resource Identifier (URI) used by the specified user ). More discussions will be held in the network chapter.

The browser parses and displays HTML files according to HTML and CSS specifications. Those standards are mainly maintained by W3C (the World Wide Web Alliance), which can be said to be an organization of web development standards.

HtmlThe latest version of the specification isHtml4 (http://www.w3.org/TR/html401),HTML5It is still being developed. Now it has been developed ).

Current CSS Version 2 (http://www.w3.org/TR)Css3It is still being developed ).

Over the years, browser vendors have followed only a few development standards and have developed their own extensions.WebDevelopers bring about serious compatibility issues. Currently, most browser vendors are more or less compliant with some standards.

The user interfaces of browsers have many things in common. The elements between these commonalities are:

Enter the URI Address Bar

Forward and backward buttons

Bookmarks

Refresh and stop buttons. They are used to refresh and stop loading the current document.

Return to the home page. You can go back to your home page

It is also strange that no formal specifications are specified on the browser user interface. These are the results of constant imitation and improvement between browser vendors. The HTML5 specification does not define the UI elements or the elements that the browser must possess, but lists some common elements. Among them are the address bar, Status Bar, and toolbar of the browser. Of course, it also has unique features, such as the Download Manager of Firefox.

For more information, see the following user interface section.

Main Components of browsers

Main Components of the browser:

1. the user interface contains the address bar of the browser, the back/forward button, and the bookmarks menu.That is, what you see is other than displaying the main window of the page you requested.

2. browser engine-interfaces used to query and operate rendering engines.

3. Rendering Engine-responsible for displaying the requested content. For example, if the request content is HTML, it is responsible for parsing HTML and CSS and displaying the parsed content on the screen.

4. Network-used to complete network calls, such as HTTP requests. It has platform-independent interfaces and can work across platforms.

5. The UI backend is used to draw basic components, such as a combination selection box. It has a common interface that is not specific to a platform and uses the user interface of the operating system at the underlying layer.

6. js interpreter-used to explain execution of JSCode

7. Data Storage-a persistent layer. The Browser needs to store data similar to cookies on the hard disk. HTML5 defines the WEB database technology, which is a lightweight and complete client storage technology.

 

Unlike most browsers, chrome allocates rendering engine instances for each tab. Each tab is an independent process.

The components that constitute the browser will be discussed in detail later.

Communication between components

Both Firefox and chrome have developed a licensed Communication Organization, which will be discussed later.

Rendering Engine

The rendering engine is responsible for rendering, that is, displaying the requested content in the browser window.

By default, the rendering engine can display HTML, XML documents, and images. It can also use plug-ins (a browser extension) to display other types of data, such as the PDF Reader plug-in, the PDF format can be displayed. A special chapter will be used to explain plug-ins and extensions. Here we will only discuss the main purpose of the rendering engine-display HTML and images after CSS is applied.

Rendering Engine