Technology Questions

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.

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.

“In software testing, a test harness or automated test framework is a collection of software and test data configured to test a program unit by running it under varying conditions and monitor its behavior and outputs. It has two main parts: the test execution engine and the test script repository.”

The backup strategies that are provided by Oracle are as follows:

- Logical backup using Exports and import.

- Physical file system backup

- RMAN Recovery Manger which is also known as incremental files system backup.

Definition: 3G, known as 3rd Generation, is a standard for mobile / cellular phones. It provides the services that fulfill the International Telecommunication Union specifications.

The application services of 3G include wireless voice telephone, mobile internet access, video calls and mobile television – all in a mobile environment.

3G allows simultaneous use of speech and data services
3G provides peak data rates of at least 200 KBits according to the IMT-2000 specification.
Mobile broadband access of several MBits to laptop computer systems, smart phones is provided by latest 3.5G, 3.75G versions.

3G standards:

UMTS:

  -  Universal Mobile Telecommunications System – One of the 3G mobile telecommunications technologies, also being developed into a 4G technology.
  -  Most common form of UMTS uses W-CDMA as an underlying air interface.
  - UMTS also covers Radio Access Network – UMTS Terrestrial Radio Access Network (UTRAN), and Mobile Application Part (MAP).
  -  Users are authenticated via USIM cards (Universal Subscriber Identity Module).

CDMA2000

   -  Also known as IMT Multi-Carrier (IMT-MC), uses CDMA channel access for sending voice, data and signaling data between mobile phones and cell sites.
   -  The standards are CDMA2000 IX, CDMA2000 EV-DOR Rev.0, CDMA2000 EV-DO Rev.A and CDMA2000 EV-Rev.B. They are approved radio interfaces for the ITU’s IMT-2000.

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One of the main causes of congestion is that traffic is often busy. If hosts could be made to transmit at a uniform rate, congestion would be less common. Another open loop method to help manage congestion is forcing the packet to be transmitted at a more predictable rate. This is called traffic shaping.

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.