var app = angular.module('myApp', [])

.run(function ($rootScope) {
  $rootScope.name = 'Pascal';
});
<!DOCTYPE html>
<html ng-app="myApp">

  <head>
    <meta charset="utf-8" />
    <title>AngularJS Plunker</title>
    <script>document.write('<base href="' + document.location + '" />');</script>
    <script data-require="angular.js@1.3.x" src="https://code.angularjs.org/1.3.0/angular.js" data-semver="1.3.0"></script>
    <script src="app.js"></script>
  </head>

  <body>
    <p>Hello {{name}}!</p>
    <button ng-click="name = 'Christoph'">Click me!</button>
  </body>

</html>