Angular's $rootScope can be used to share information between the app's components (besides other uses). It is discouraged to rely upon it too much because it could become polluted or difficult to trace up and down the app's entire scope 'stack'. But if you really need or want to set 'global' data, it works:
In your new plunkr, you are using both ng-model and ng-value for the text input. Remove the ng-value altogether. (It is used typically for elements that have 'value' properties, like radio buttons and checkboxes, where the 'value' is 'checked' or 'selected', etc.) ng-model is what you want.
http://plnkr.co/edit/DnzOdRicXLHtg4DqoVdJ?p=preview
name is :{{$root.name}}
username is :{{$root.uname}}
and
Name:
You entered: {{$root.name}}