AlertDialog : An alert dialog box supports 0 to 3 buttons and a list of selectable elements, including check boxes and radio buttons. Among the other dialog boxes, the most suggested dialog box is the alert dialog box.

ProgressDialog: This dialog box displays a progress wheel or a progress bar. It is an extension of AlertDialog and supports adding buttons.

DatePickerDialog: This dialog box is used for selecting a date by the user.

TimePickerDialog: This dialog box is used for selecting time by the user.

Multiple choice list can be viewed by making the CheckBox android:id value be “@android:id /text1". That is the ID used by Android for the CheckedTextView in simple_list_item_multiple_choice.

Android Application Architecture has the following components:
* Services – like Network Operation
* Intent - To perform inter-communication between activities or services
* Resource Externalization - such as strings and graphics
* Notification signaling users - light, sound, icon, notification, dialog etc.
* Content Providers - They share data between applications

Android is a stack of software for mobile devices which has Operating System, middleware and some key applications. The application executes within its own process and its own instance of Dalvik Virtual Machine. Many Virtual Machines run efficiently by a DVM device. DVM executes Java language’s byte code which later transforms into .dex format files.

Features of Android :

- Components can be reused and replaced by the application framework.
- Optimized DVM for mobile devices
- SQLite enables to store the data in a structured manner.
- Supports GSM telephone and Bluetooth, WiFi, 3G and EDGE technologies
- The development is a combination of a device emulator, debugging tools, memory profiling and plug-in for Eclipse IDE.

It is advisable to use container classes of the STL so that you don’t have to go through the pain of writing the entire code for handling collisions, making sure its working well, testing it repeatedly with an overhead of time consumption.

Suppose you have some data that has values associated with strings and its fields consist of grades> in this situation you can directly use hash table instead of having it created by yourself.

Function prototyping is a function declaration statement that tells the compiler about the return type of the function and the number as well as type of arguments required by the function at the time of calling it.

Syntax:

return_type function_name( type1 arg1, type 2 arg2, ... );

Advantages of function prototype :

- It helps the compiler in determining whether a function is called correctly or not. Each time when a function is called, its calling statement is compared with its prototype. In case of any mismatch, compiler reports an error.

- A function must be defined before calling it. But prototyping allows a function to be called before defining it.

Polymorphism is also achieved in C++ using virtual functions. If a function with same name exists in base as well as parent class, then the pointer to the base class would call the functions associated only with the base class. However, if the function is made virtual and the base pointer is initialized with the address of the derived class, then the function in the child class would be called.

Scope resolution operator allows a program to reference an identifier in the global scope that is hidden by another identifier with the same name in the local scope.