Internal static variable vs. External static variable with Examples in C

The static variable may be internal or external depending on the place of declaration. Both kinds of static variables are stored in initialized data segments.

Internal Static Variables

Internal Static variables are defined as those having static variables which are declared inside a function and extend up to the end of the particular function.

Syntax:

 main( ) 
{
  static datatype variable;
  // other statements
}

Example:

C

// C program to demonstrate
// Internal Static Variables

#include <stdio.h>

int value();

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

int value()
{
    static int a = 5;
    return a;
}

Output

5

External Static Variables

External Static variables are those which are declared outside a function and set globally for the entire file/program.

Syntax:

 
static datatype variable;

main()
{
  statements
}

function1()
{
  statements
}

Example:

C

// C program to demonstrate
// External Static Variables

#include <stdio.h>

int add(int, int);

static int a = 5;

int main()
{
    int c;
    printf("%d", add(a, c));
}

int add(int c, int b)
{
    b = 5;
    c = a + b;
    return c;
}

Output

10

Difference between Internal Static Variables and External Static Variables

Following are some major differences between internal static and external static variables:

Parameter	Internal Static Variables	External Static Variables
Keyword	”static”	”static”
Linkage	Internal static variable has internal linkage.	External static variables has internal linkage.
Declaration	Internal static variables are declared within a function.	External static variables are declared outside any function.
Comparison	Internal static variables are local variables.	External static variables are similar to global variables.
Visibility	Internal static variables are accessible only in their particular function.	External Static variables are accessible only from within the file of their declaration.
Lifetime	The storage duration of Internal static variables is throughout the whole program.	The storage duration of external static variables is throughout the whole program.
Scope	Function of the variable’s declaration.	File of the variable’s declaration.