upgrading Xcode

I am currently working with Xcode 3.1.3 , i wanted to upgrade it to new 开发者_运维百科version of Xcode 4.0.My question is will i be able to run my older applications which were built on Xcode 3.1.3 on the new version of Xcode.

Thanks in advance

Yes you will be able to do so. However PPC support and 10.4 support is dropped on the mac. If you want to play safe, you can install Xcode 4 in a separate location leaving your Xcode 3.1.3 untouched, so you can switch between these two.

The project format of Xcode 3.2 and Xcode 4 is the same.

One option is to install Xcode 4 into another directory. I just installed the latest version yesterday and it offers you this option. Here is a link here about this also. There is also a StackOverflow question here. If everything works as you expect you can delete Xcode 3.1.3. If not, you still have your current version around.