Declaration of const data member
const int x = 10;once you have initialized x you can not reassign its value
value can not be changed
initialization is not same as assignment
const int x = 20; //initialization
x = 20; // assignmentexample of constant value is pi = 3.14
we can initialize const members from both inside and outside of class
We can initialize const variable from outside of the class also, like passing value from main as parameter
Initializer list is used to define const members from outside of the class
How to initialize const data member outside of a class
for that you must use initializer list
#include <iostream> using namespace std; class A{ public: const int a; // A(int b){ // a = b; // } A(int b) : a(b) {}; //initializer list void show(){ cout<<a; } // void changename(){ // a = 45; //} //error: assignment of read-only member ‘A::a’ }; int main() { A obj(5),obj2(6); obj2.show(); obj.show(); return 0; } //output : 65 
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