Variable and scope beyond file . cpp C++

Question

Is there a possibility of a file . cpp "seeing" a variable declared in in another file . cpp? Example: in the main.cpp file there is a global variable int myVar. You can access it in another file, in my.cpp?

Answer 1

Variables declared in global scope of the file can be accessed by other files using extern.

foo.cpp

int myVar = 10;

main.cpp

#include <iostream>

extern int myVar;

int main() {
  std::cout << myVar << std::endl;

  return 0;
}

To share variables it is recommended to declare them in header files. h, and they must also be constant or pre-processed to not interfere with the behavior of the other functions that depend on them.