Objective-C property and synthesize logic

Question

What is an actual name of instance variable, say, topSpeed, as from lectures of Stanford University about the Objective-C and iOS development?

Here is the code:

Answer 1

1. It's a syntax sugar, let you type less word.
2. Unlike java/c++, in obj-c you can't access variable of class. You could only call It's methods.
3. @synthesize topSpeed = _topSpeed means You want an variable named _topSpeed and has Accessors named topSpeed and setTopSpeed.

4. @property (nonatomic) double topSpeed; is not a pure variable declaration, It will also declare Accessors too. A pure variable of a class Foo will look like this :

   @interface Foo:NSObject{ double topSpeed; }