Global variables
suggest changeTo declare a single instance of a variable which is accessible in different source files, it is possible to make it in the global scope with keyword extern
. This keyword says the compiler that somewhere in the code there is a definition for this variable, so it can be used everywhere and all write/read will be done in one place of memory.
// File my_globals.h:
#ifndef __MY_GLOBALS_H__
#define __MY_GLOBALS_H__
extern int circle_radius; // Promise to the compiler that circle_radius
// will be defined somewhere
#endif
// File foo1.cpp:
#include "my_globals.h"
int circle_radius = 123; // Defining the extern variable
// File main.cpp:
#include "my_globals.h"
#include <iostream>
int main()
{
std::cout << "The radius is: " << circle_radius << "\n";'
return 0;
}
Output:
The radius is: 123
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