Question

How to define and use global variable in C

Answer 1

#include <stdio.h>

void function1(void);
void function2(void);

int g_n;

int main(int argc, char **argv) 
{ 
    g_n = 0;
    printf("g_n = %d\n", g_n); // 0
    
    function1();
    printf("g_n = %d\n", g_n); // 100
 
    function2();
    printf("g_n = %d\n", g_n); // 12345
    
    g_n = 77;
    printf("g_n = %d\n", g_n); // 77
    
    g_n = 999; // this value (999) will change to 100 in function1()
    function1();
    printf("g_n = %d\n", g_n); // 100
    
    return(0);
}

void function1(void)
{
   g_n = 100;
}

void function2(void)
{
   g_n = 12345;
}

/*
run:

g_n = 0
g_n = 100
g_n = 12345
g_n = 77
g_n = 100

*/

 

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