Some questions about the Crystal ball app xcode

@implementation ViewController

    - (void)didReceiveMemoryWarning
    {
    [super didReceiveMemoryWarning];
    // Release any cached data, images, etc that aren't in use.
    }

    #pragma mark - View lifecycle

    - (void)viewDidLoad
   {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
   }

  - (void)viewDidUnload
  {
    [super viewDidUnload];
    // Release any retained subviews of the main view.
    // e.g. self.myOutlet = nil;
  }

    - (void)viewWillAppear:(BOOL)animated
 {
    [super viewWillAppear:animated];
 }

  - (void)viewDidAppear:(BOOL)animated
 {
    [super viewDidAppear:animated];
 }

    - (void)viewWillDisappear:(BOOL)animated
   {
    [super viewWillDisappear:animated];
  }

   - (void)viewDidDisappear:(BOOL)animated
   {
    [super viewDidDisappear:animated];
   }

    - (BOOL)shouldAutorotateToInterfaceOrientation:    (UIInterfaceOrientation)interfaceOrientation
    {
    // Return YES for supported orientations
    return (interfaceOrientation != UIInterfaceOrientationPortraitUpsideDown);
    }

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end