How to call a global variable in to function in C? - c

Question

I'm starting at the word of programming so I'm reading a book about programming in C, it says that if I want to call a global variable into a function I need to call the global variable with (::) before the name... in terminal shows this:
funcion2.c:17:57: error: expected expression before ‘::’ token
17 | printf("value of global variable is %d\n",::k);
thaks.
#include <stdio.h>
void f1(void);
int K=5;
void main()
{
int I;
for(I=1; I<=3; I++)
{
f1();
}
void f1(void)
{
int k=2;
K+=K;
printf("VALUE IS: %d\n",k);
::K=::K+K; // <-
printf("VALUE IS %d\n",::k); // <-
}
}

Answer 1

The global variable is called before the main() function, and that beeing said, heres an example of programm using global variable in main() and in funtions:
#include<stdio.h>
void func_1();
void func_2();
int a, b = 10; // declaring and initializing global variables
int main()
{
printf("Global a = %d\n", a);
printf("Global b = %d\n\n", b);
func_1();
func_2();
// signal to operating system program ran fine
return 0;
}
void func_1()
{
printf("From func_1() Global a = %d\n", a);
printf("From func_1() Global b = %d\n\n", b);
}
void func_2()
{
int a = 5;
printf("Inside func_2() a = %d\n", a);
}
Output:
Global a = 0
Global b = 10
From func_1() Global a = 0
From func_1() Global b = 10
Inside func_2() a = 5
In line 4, a and b are declared as two global variables of type int. The variable a will be automatically initialized to 0. You can use variables a and b inside any function. Notice that inside function func_2() there is a local variable with the same name as a global variable. When there is a conflict between the global variable and local variable, the local variable gets the precedence, that's why inside the func_2() value of local variable a is printed.
Unlike local variables, global variables are not destroyed as soon as the function ends. They are available to any function until the program is executing.