I am unable to call a funtcion from one file to another, eventhough both the files are in same workspace

Question

File_1.c:

#include <stdio.h>
#include <stdlib.h>

int main()
{
    int value;
    value = increment();
    value = increment();
    value = increment();

    printf("%d", value);
    return 0;
}

File_2.c:

static int var;
int increment()
{
    var = var+1;
    return var;
}

I was trying to execute File_1.c,

But the below error I am getting implicit declaration of function 'increment' [-Wimplicit-function-declaration] value = increment();

I am trying in Visual Studio Code. Both the files are in same workspace.

Do I need to do something in vscode for that since I am able to get output in code blocks ?