What is the difference between writing iPhone applications?

I started learning about iPhone today.

Book: begining iPhone 3 development_embedding ing the iPhone SDK (Basic tutorial for iPhone 3 Development)

 

What is the difference between writing iPhone applications?
1. There is only one running application
2. There is only one "window"
3. Restricted Access
You can only read and write files in the file system created for the application on the iPhone. This area is called the sandbox of the application. You cannot access a network port with a small port number on the iPhone, or perform any operation on a desktop computer that requires root user or administrator permissions.
4. limited response time
5. Limited screen size
IPhone display screen 320*480 pixels
6. Limited system resources
7. Garbage collection is not supported
8. distinctive methods
The iPhone does not have a keyboard or mouse, which means it interacts with users in a different way than a common computer. Fortunately, most interactions do not need to be handled by you.