angular-cn/aio/content/tutorial/toh-pt0.md

# The Application Shell

## Install the Angular CLI

 Install the [Angular CLI](https://github.com/angular/angular-cli), if you haven't already done so.

<code-example language="sh" class="code-shell">
  npm install -g @angular/cli
</code-example>  

## Create a new application

Create a new project named `angular-tour-of-heroes` with this CLI command.

<code-example language="sh" class="code-shell">
  ng new angular-tour-of-heroes
</code-example> 

The Angular CLI generated a new project with a default application and supporting files. 

## Serve the application

Go to the project directory and launch the application.

<code-example language="sh" class="code-shell">
  cd angular-tour-of-heroes
  ng serve --open
</code-example>
 
<div class="l-sub-section">

The `ng serve` command builds the app, starts the development server,
watches the source files, and rebuilds the app as you make changes to those files.

The `--open` flag  opens a browser to `http://localhost:4200/`.

</div>

You should see the app running in your browser.

## Angular components

The page you see is the _application shell_.
The shell is controlled by an Angular **component** named `AppComponent`.

_Components_ are the fundamental building blocks of Angular applications.
They display data on the screen, listen for user input, and take action based on that input.

## Change the application title

Open the project in your favorite editor or IDE and navigate to the `src/app` folder.

You'll find the implementation of the shell `AppComponent` distributed over three files:

1. `app.component.ts`&mdash; the component class code, written in TypeScript. 
1. `app.component.html`&mdash; the component template, written in HTML.
1. `app.component.css`&mdash; the component's private CSS styles.


Open the component class file (`app.component.ts`) and change the value of the `title` property to 'Tour of Heroes'.

<code-example path="toh-pt0/src/app/app.component.ts" region="set-title" title="app.component.ts (class title property)" linenums="false">
</code-example>

Open the component template file (`app.component.html`) and
delete the default template generated by the Angular CLI.
Replace it with the following line of HTML.

<code-example path="toh-pt0/src/app/app.component.html" 
  title="app.component.html (template)" linenums="false">
</code-example>

The double curly braces are Angular's *interpolation binding* syntax. 
This interpolation binding presents the component's `title` property value 
inside the HTML header tag.

The browser refreshes and displays the new application title.

{@a app-wide-styles}

## Add application styles

Most apps strive for a consistent look across the application.
The CLI generated an empty `styles.css` for this purpose.
Put your application-wide styles there.

Here's an excerpt from the `styles.css` for the _Tour of Heroes_ sample app.

<code-example path="toh-pt0/src/styles.1.css" title="src/styles.css (excerpt)">
</code-example>

## Final code review

The source code for this tutorial and the complete _Tour of Heroes_ global styles 
are available in the <live-example></live-example>. 

Here are the code files discussed on this page. 

<code-tabs>

  <code-pane title="src/app/app.component.ts" path="toh-pt0/src/app/app.component.ts">
  </code-pane>

  <code-pane title="src/app/app.component.html" path="toh-pt0/src/app/app.component.html">
  </code-pane>

  <code-pane 
    title="src/styles.css (excerpt)" 
    path="toh-pt0/src/styles.1.css">
  </code-pane>
</code-tabs>

## Summary

* You created the initial application structure using the Angular CLI.
* You learned that Angular components display data.
* You used the double curly braces of interpolation to display the app title.