using same variable in diffrent source files C++

Question

Is there any way to use from two diffrent source files the same instance of variable in C++ ?

for example,if I have

source1.cpp

x = true;
while (x) 
{

}

source2.cpp

x = false;

then if I run first source1.cpp,there is infinite loop,and after runing source2.cpp from diffrent terminal,the loops end,due to x changes.

thanks.

just to make it clear : those are two main files compiled separate from each other and run at the same time from two diffrent terminals

Answer 1

"The global variable should be declared extern in a header file included by both source files, and then defined in only one of those source files" Check out this post