Technology Questions

PEAR(PHP Extension and Application Repository) is a framework and repository for reusable PHP components. PEAR is a code repository containing all kinds of php code snippets and libraries. 

PEAR also offers a command-line interface that can be used to automatically install "packages".

Function is an algorithm which can be used any where in the program when required

Structure: Initially (in C) a structure was used to bundle different type of data types together to perform a particular functionality. But C++ extended the structure to contain functions also. The major difference is that all declarations inside a structure are by default public.
Class: Class is a successor of Structure. By default all the members inside the class are private.

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.

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.

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.