C++ const Keyword | Find output programs | Set 1

Answer Program 1:

Output:

[Error] non-member function 'void fun(int)' cannot have const qualifier.

Explanation:

The above code will generate an error because we cannot define, the non-member function as a const. Without a const keyword the above code will work fine.

Answer Program 2:

Output:

error: invalid conversion from ‘const int*’ to ‘int*’ [-fpermissive] ptr = &X;

Explanation:

The above program will generate an error in C++, C++ does not allow modification in a constant using pointer, but we can modify the value of a constant in C language. The below program in C language will work fine.

#include <stdio.h>

int main()
{
    const int X = 0;
    int* ptr;

    ptr = &X;
    *ptr = 10;

    printf("%d", X);

    return 0;
}

Program may run on C language compiler, but it is not a standard that we can change the constant. In C language compiler – it can be changed through the pointer.

Answer Program 3:

Output:

10 20

Explanation:

The above code will print "10 20" on the console screen.

Let's understand the program step by step.

Here we created a class Sample that contains two const data members A and B. As we know that we can assign the values of constant at the time of declaration. But here we use the concept of member initialize list.

Sample ():A(10),B(20)
{
}

We can assign value to const data members using the member initialize list. We can initialize members by a colon (:) with members and value in the constructor.

Here we also defined a print() member function, which is used to print values of data members.