Answer 1

Data abstraction refers to, providing only essential information to the outside world and hiding their background details, i.e., to represent the needed information in program without presenting the details.

Data abstraction is a programming (and design) technique that relies on the separation of interface and implementation.

In C++, we use classes to define our own abstract data types (ADT). You can use the cout object of class ostream to stream data to standard output like this:

#include <iostream> using namespace std; int main( ) { cout << "Hello C++" <<endl; return 0; }

Here, you don't need to understand how cout displays the text on the user's screen. You need to only know the public interface and the underlying implementation of cout is free to change.

Any C++ program where you implement a class with public and private members is an example of data abstraction. Consider the following example:

#include <iostream>
using namespace std;
class Adder
{
public: // constructor
Adder(int i = 0)
{
total = i;
} // interface to outside world
void addNum(int number)
{
total += number;
} // interface to outside world
int getTotal()
{
return total;
};
private: // hidden data from outside world
int total;
};
int main( )
{
Adder a;
a.addNum(10);
a.addNum(20);
a.addNum(30);
cout << "Total " << a.getTotal() <<endl;
return 0;
}

When the above code is compiled and executed, it produces the following result:

Total 60

Above class adds numbers together, and returns the sum. The public members addNum and getTotal are the interfaces to the outside world and a user needs to know them to use the class. The private member total is something that the user doesn't need to know about, but is needed for the class to operate properly.