Const Functions in C++

The Const member functions are used to prevent modifications of class data members within it.Likewise,the const parameters are used to prevent modification of data collected by them.

class sample
{
     int i;
     public:
               int fun() const
               {
                      i=82;   //error
                      return i;
               }
               void fun1(const int &ii)
               {
                      ii=8;    //error
               }
};
void main()
{
      sample s;
      int p=9;
      p=s.fun();
      s.fun1(p);
}

Here fun() is a const member function.Hence ,compiler flashes an error when we try to modify the data member i.Similarly,the function fun1() cannot modify the value of ii as ii is declared as const.