Member Initialization Lists

 #include <iostream.h>
/*********************************************
 File: constmember1.C
 This program demonstrates the problem of
 initializing const data members
*********************************************/

class ABC{
	const int x;
	const int y;
public:
	ABC(int ,int );
	void get_xy(int& ,int& );
};

ABC::ABC(int var1, int var2)
{
	cout << "Constructing..." << endl;
	x = var1;
	y = var2;
}

void ABC::get_xy(int& var1, int& var2)
{
	var1=x; var2=y;
}

int main()
{
	int var1, var2 ;
	ABC object1(10, 20);
	object1.get_xy(var1, var2);
	cout << "X = " << var1 << " Y = " << var2 << endl;

	return(0);
}

Compile Time Error:
constmember1.C: In method `ABC::ABC(int, int)':
constmember1.C:20: assignment of read-only member `int ABC::x'
constmember1.C:21: assignment of read-only member `int ABC::y'

#include<iostream.h>
/*********************************************
 File: constmember.C
 This program demonstrates the use of member
 initialization lists.
*********************************************/

class ABC{
	const int x;
	const int y;
public:
	ABC(int ,int );
	void get_xy(int& ,int& );
};

ABC::ABC(int var1, int var2) : x(var1), y(var2) // x and y are initialized
here
{
	cout << "Constructing..." << endl;
}

void ABC::get_xy(int& var1, int& var2)
{
	var1=x; var2=y;
}

int main()
{
	int var1, var2 ;
	ABC object1(10, 20);
	object1.get_xy(var1, var2);
	cout << "X = " << var1 << " Y = " << var2 << endl;

	return(0);
}