Global variables

[obeeey]

Hello,
I have a problem with declaring a variable which can be used in functions.
Let's say I want to do something like this:

int G_NUMBER; //a global variable (being initialized with 0)
int main()
{
int number;
cin >> number;

G_NUMBER = number; // ERROR - how to change G_NUMBER value? 

return 0;
}

I want to use the same value of G_NUMBER as a CONST value in a lot of functions, but I can't use #DEFINE for this because this value is from input.
How can I do it so other functions will see this value which was from input?
Thanks!

[deleted account xyzzy]

Your compiler should not be having a problem with line 7.

#include <iostream>

int G_NUMBER { };

void aFunc();

int main()
{
   std::cout << "In main: " << G_NUMBER << "\n\n";

   aFunc();

   std::cout << "Enter a number for the global: ";
   int number { };
   std::cin >> number;
   std::cout << '\n';

   G_NUMBER = number; // no error

   aFunc();

   std::cout << "In main: " << G_NUMBER << '\n';
}

void aFunc()
{
   std::cout << "In aFunc: " << G_NUMBER << "\n\n";
}

In main: 0

In aFunc: 0

Enter a number for the global: 12

In aFunc: 12

In main: 12

Using globals has a trap, the value(s) can be change anywhere in your code. That makes tracking "wrong" values hard to do.

Passing local variables by pointer or reference is preferred over using globals.