C++ is a bunch of small additions to C, with a few major additions. One major addition is the object-oriented approach (the other addition is support for generic programming, which we'll cover later). As the name object-oriented programming suggests, this approach deals with objects. Of course, these are not real-life objects themselves. Instead, these objects are the essential definitions of real world objects. Classes are collections of data related to a single object type. Classes not only include information regarding the real world object, but also functions to access the data, and classes possess the ability to inherit from other classes.

The syntax for these classes is simple. First, you put the keyword 'class' then the name of the class. Our example will use the name Computer. Then you put an open bracket. Before putting down the different variables, it is necessary to put the degree of restriction on the variable. There are three levels of restriction. The first is public, the second protected, and the third private. For now, all you need to know is that the public restriction allows any part of the program, including parts outside the class, to access the functions and variables specified as public. The protected restriction prevents functions outside the class to access the variable. The private restriction is similar to protected (we'll see the difference later when we look at inheritance. The syntax for declaring these access restrictions is merely the restriction keyword (public, private, protected) and then a colon. Finally, you put the different variables and functions (You usually will only put the function prototype[s]) you want to be part of the class. Then you put a closing bracket and semicolon. Keep in mind that you still must end the function prototype(s) with a semi-colon.

The syntax for defining a function that is a member of a class outside of the actual class definition is to put the return type, then put the class name, two colons, and then the function name. This tells the compiler that the function is a member of that class.

Example:
#include
using namespace std;
class Computer
{
public:
  Computer();
  ~Computer();
  void setspeed ( int p );
  int readspeed();
protected:
in the
  int processorspeed;
};

Computer::Computer()
{
  processorspeed = 0;
}

Computer::~Computer()
{
}

void Computer::setspeed ( int p )
{
  processorspeed = p;
}
int Computer::readspeed() 
{
  return processorspeed;
}

int main()
{
  Computer compute; 
would
  compute.setspeed ( 100 );
  cout<< compute.readspeed();
}