![using-new-iphone-sdk-develop-old-iphone-app](https://www.memorylack.com/wp-content/uploads/2010/08/objective-c.png)
New iPhone SDK 4 was released. If your iPhone have not update to iOS4 and you already update to new iPhone SDK. I have a method to use new iPhone SDK to deploy an application can be used in old iPhone system.
First, you should open a project setting:
Enter deployment in the search field, you can find iPhone OS Deployment Target: