What is your default XCode Version(if you have many)   Default XCode version from Terminal Command:  > xcodebuild -showsdks    If XCode 7.2 installed and assigned from XCode Preferences as default like below:       Run the Command:  > xcodebuild -showsdks  OS X SDKs:     OS X 10.11                        -sdk macosx10.11 iOS SDKs:     iOS 9.2                           -sdk iphoneos9.2 iOS Simulator SDKs:     Simulator - iOS 9.2               -sdk iphonesimulator9.2 tvOS SDKs:     tvOS 9.1    ...

  iOS - Objective C @Single Glance  with Ry's detailed  Figures What an Objective C can do?   What is the Relationship between Objective C and C programming Language?     How Objective Class Looks Like?     How a Property Looks Like? How methods (Functions in C) looks like?    "Categories" in Objective C :    "Protocols" in Objective C : If you want to know the complete theory of above figures, you can have a look @ http://rypress.com/tutorials/objective-c/index  

UIKIT Framework Hierarchy

                       Foundation Framework Classes Hierarchy

                ****************  Do you want fancy Text    *************** #import "ViewController.h" @interface ViewController () @property (weak, nonatomic) IBOutlet UILabel *myLabel; @end @implementation ViewController - (void)viewDidLoad {        [super viewDidLoad];        // Do any additional setup after loading the view, typically from a nib.        NSString *myString = @"That is a test attributed string.";           NSMutableAttributedString *str = [[NSMutableAttributedString alloc] initWithString:myString];         [str addAttribute:NSBackgroundColorAttributeName value:[UIColor yellowColor] range:NSMakeRange(3,5)];         [str addAttribute:NSForegroundColorAttributeName value:[UICo...

  Foundation Framework is Foundation for making       iOS Applications  The Foundation framework defines a base layer of Objective-C classes.  The Foundation framework is designed with these goals in mind: Provide a small set of basic utility classes. Make software development easier by introducing consistent conventions for things such as deallocation. Support Unicode strings, object persistence, and object distribution. Provide a level of OS independence, to enhance portability. The Foundation framework includes the root object class, classes representing basic data types such as strings and byte arrays, collection classes for storing other objects, classes representing system information such as dates, and classes representing communication ports.  "An immutable string is a text string that is defined when it is created and subsequently cannot be changed. An immutable string is implemented as an array of Unicode ch...

Here are the Quick Difference between Serial & Concurrent Queues  Above image has taken from AppCoda