Now that we have covered the basics, let's go back and give it some polish. Did you play with it enough to know what needs to be improved? Here are a few of the obvious ones that I will address.
There is no application icon. When you select the application on the simulator, there is a plain black window icon—a default icon supplied by the operating system if an icon is not presented.
The name of the application is the same as the project name. This isn't horrible, but it could be better.
The edit field on the application for the bill amount will accept any value. The bill amount needs to be limited to valid numbers.
When exiting the application, a standard save prompt is shown. This is not useful, and is annoying, so it should be removed.
So let's start going through and addressing these issues!