When to use extern in C++

Question

I\'m reading \"Think in C++\" and it just introduced the extern declaration. For example:

extern int x;
extern float y;

I thi

Answer 1

It is useful when you share a variable between a few modules. You define it in one module, and use extern in the others.

For example:

in file1.cpp:

int global_int = 1;

in file2.cpp:

extern int global_int;
//in some function
cout << "global_int = " << global_int;