How to initialize const variable in C++?

In C++, const keyword is used to create the one time initializer and read-only variable. Once intialised, it is not legal to change the value later. There are two ways to initiaze the const varaibles in C++.

• Using initialisation list
• Using static keyword 

Example:

class cns
{
  private:
    const int val; // declaring const variable
    const static int st=10;   //declaring n initializing using static keyword
  public:
    cns(int aa = 0) :val(aa) // initializing using initialization list
    {
    }
};
main()
{
    cns con(10);
}

P.S: if const variables are not initialised, the values are undefined and it will not allow to change the values. So it is mandatory to initialize the const variables.