Technology Questions

IUnknown as an interface of a COM object. Every COM object has to support IUnknown, besides optionally adding other interfaces.

IUnknown is made of QueryInterface, AddRef and Release.

- Web browser functions are to provide the resources or information to the user when asked by them. 

- It processes the user inputs in the form of URL like https://www.google.com in the browser and allows the access to that page. 

- URL is used to identify the resources and fetch them from the server and displays it to the client. 

- It allows the user to interact with the web pages and dynamic content like surveys, forms, etc. 

- It also allows the user to navigate through the complete web page and see its source code in the HTML format. 

- It provides security to the data and the resources that are available on the web that is by using the secure methods.

Catalog views return information that is used by the SQL Server Database Engine. Catalog Views are the most general interface to the catalog metadata and provide the most efficient way to obtain, transform, and present customized forms of this information. All user- available catalog metadata is exposed through catalog views.

Bitmap indexes make use of bit arrays (bitmaps) to answer queries by performing bitwise logical operations.

Bitmap indexes are useful in the data warehousing applications.

Bitmap indexes have a significant space and performance advantage over other structures for such data.

Tables that have less number of insert or update operations can be good candidates.

The advantages of Bitmap indexes are:

   - They have a highly compressed structure, making them fast to read.

   - Their structure makes it possible for the system to combine multiple indexes together so that they can      access the underlying table faster.

The Disadvantage of Bitmap indexes is:

  - The overhead on maintaining them is enormous. 

ArrayList and LinkedList both implements List interface and maintains insertion order. Both are non synchronized classes.

But there are many differences between ArrayList and LinkedList classes that are given below.

ArrayList    V/s     LinkedList ::

1) ArrayList internally uses dynamic array to store the elements.

                   Whereas

LinkedList internally uses doubly linked list to store the elements.

2) Manipulation with ArrayList is slow because it internally uses array. If any element is removed from the array, all the bits are shifted in memory.

                   Whereas

Manipulation with LinkedList is faster than ArrayList because it uses doubly linked list so no bit shifting is required in memory.

3) ArrayList class can act as a list only because it implements List only.

                   Whereas

LinkedList class can act as a list and queue both because it implements List and Deque interfaces.

4) ArrayList is better for storing and accessing data.

                   Whereas

LinkedList is better for manipulating data.

The Singleton design pattern ensures a class only has one instance, and provides a global point of access to it. The class keeps track of its sole instance and ensures that no other instance can be created. Singleton classes are appropriate for situations where it makes sense for a single object to provide access to a global resource.Several Cocoa framework classes are singletons. They includeNSFileManager, NSWorkspace, NSApplication, and, in UIKit,UIApplication. A process is limited to one instance of these classes. When a client asks the class for an instance, it gets a shared instance, which is lazily created upon the first request.

A Thread is a block of code that can be executed in parallel with another block of code.

Some of the rules which should be followed while naming a variable in VB are as follows: 

1) Characters should be less than 255.

2) Space between characters should be allowed.

3) A variable should begin with a number.

4) Period may not be permitted.