why archive? how does it improve performance? iOS
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I've seen some of the example of using NSCoder to archive the things in your application 

    @interface MyApplicationData : NSObject <NSCoding, NSCopying> {
        NSMutableArray* items;
        NSMutableArray* categories;
    }

Please see this thread. http://stackoverflow.com/questions/1701582/how-to-use-nscoder

Why does this improve the performance of your app? isn't that doing more things in your application? Can anyone tell me why and when you want to use archive? 

Thanks in advance. 