The IOS Application Model Compared To Android

The Application Model

 

To begin with, note that the operating system on your iOS device starts a set
of system programs when the device boots. This set of programs, which you
can think of as the iOS runtime system, runs constantly in the background
and manages every app that is run.
Technically, your app is nothing more than an executable program (like an
.exe on Windows) that runs on the device and interacts with the iOS runtime
system. The home screen on the iOS device simply shows icons for all such
executable programs. When an icon is clicked, the operating system launches
the executable corresponding to the icon and causes the program to run on
the iOS device.
In other words, an iOS app is just a program that runs on the device — a pretty
straightforward beast.
An Android app, on the other hand, consists of a set of Java classes that are
loaded by and encapsulated inside the Android runtime system. This Android
runtime system is a Java program that runs on the Java virtual machine.
When the app is built, it’s linked with a standard main program along with an
app-specific component generated by the Xcode IDE known as the app delegate.
The main program and the app delegate together serve as the interface
between your app and the iOS runtime. These components deal with user
interface events, such as touches, and system events such when your app
goes into the background — for example, because of a user’s action or maybe
an e-mail