> 
> **Possible Duplicate:**  
> 
> [How does an underscore in front of a variable in a cocoa objective-c class work?](https://stackoverflow.com/questions/822487/how-does-an-underscore-in-front-of-a-variable-in-a-cocoa-objective-c-class-work) 
> 
> 
> 

I am new to iphone development.I am doing research on voice recording in iphone .I have downloaded the "speak here" sample program from Apple.It consist of LevelMeter.h file, in which

```
 @interface LevelMeter : UIView {

CGFloat                     _level, _peakLevel;

   }

```

The property are set as 

```
 @property                      CGFloat level;
 @property                      CGFloat peakLevel;

```

What is the use of declaring a varible like \_level and setting its property as level.Please explain me.Thanks.