NSArray (which is what NSMutableArray derives from) has a "writeToURL:atomically:
" method, which takes a file URL.
Now, if your array contains ONLY objects of the Objective-C types NSString, NSData, NSDate, NSNumber, NSArray or NSDictionary, you should be okay. If you have some custom objects, you'll need to write archiving / unarchiving coder methods which will allow those custom object's data to be written out to a file and read from a file.