Why static data member is showing this error?

Question

I was learning static data members in c++ and I wrote this code but on compilation, it is giving me this error:

main.cpp:21:12: error: ‘int Test1::a’ is private within this context

 Test1::a=50;
        ^

main.cpp:17:5: note: declared private here int Test1::a;

But I don't know why this error is coming and how to solve this.

#include <iostream>
using namespace std;

class Test1{
    static int a; //declaration
};
int Test1::a; // definition

int main()
{
    Test1::a=50;
    cout<<"a= "<<Test1::a<<endl;
}

Answer 1

You declared static int a as private member in the class, which can be accessed only within class. Class members are private by default. You should have declared it as public.

class Test1{
public:
    static int a; //declaration
};
int Test1::a=0;
.
.
.
.
//whatever