Question

This variable is defined in xyz.cpp

const int i = 10;

The below main() method is written in abc.cpp

void main()
{
    cout<<i; //trying to access 'i' from a different .cpp file
}

Answer 1

You need to declare it extern in abc.cpp:

extern const int i;

EDIT: As stated in the comment below, in C++ (unlike C), to give a const variable external linkage, you need to declare it es extern also in xyz.cpp:

extern const int i = 10;

Reference: MSDN