根目录：NSHomeDirectory();

     Documents：NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES).lastObject;

     Library
           Caches：NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES).lastObject;
           Preferences：
                 // 偏好设置
                 NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
                 NSString *name = @"zhangsan";
                 [defaults setObject:name forKey:@"NAME"];
                 // 读取偏好设置
                 NSString *str = [defaults objectForKey:@"NAME"];

      tmp：NSTemporaryDirectory();