How to declare a global variable that could be used in the entire program

Question

I have a variable that I would like to use in all my classes without needing to pass it to the class constructor every time I would like to use it. How would I accomplish th

Answer 1

// L.hpp
struct L { static int a; };

// L.cpp
int L::a(0);

Answer 2

keyword extern

//file1.cpp

int x = 0;

//file1 continues and ends.


//file2.cpp

extern int x; //this gets tied into file1.cpp's x at link time.

//file2.cpp goes on and ends

Answer 3

Declare the variable as extern in a common header.

Define it in any source file.