static

static keyword is used to declear static variable.

Syntax

static data_type var_name;

Declearation of static variable

static int score;

Properties of static variable:

local static variable visiblity will be within block. global decleared variable having global visiblity.
scope of an static variable will always whole program.
static variable gets memory at compile time
static can be used with all data types
default initial value of static variable are zero for integral data type and NULL for others
same ststic variable can be decleared many time but it should initilize only one time throught whole program.

Guess the output #1

#include <stdio.h>

static int foo;

int main()
{
	static int foo = 10;

	printf("foo: %d\n", foo);

	return 0;
}

Compiling this code produces following output. click on below icon to see the output.

foo: 10

Explanation: None.

Guess the output #2

#include <stdio.h>

static int foo = 10;

int main()
{
	static int foo;

	printf("foo: %d\n", foo);

	return 0;
}

Compiling this code produces following output. click on below icon to see the output.

foo: 0

Explanation: None.

Guess the output #3

#include <stdio.h>

static int foo = 10;

int main()
{
	static int foo = 20;

	printf("foo: %d\n", foo);

	return 0;
}

Compiling this code produces following output. click on below icon to see the output.

foo: 20

Explanation: None.

Guess the output #4

#include <stdio.h>

static int foo;
static int foo = 10;

int main()
{
	printf("foo: %d\n", foo);

	return 0;
}

Compiling this code produces following output. click on below icon to see the output.

foo: 10

Explanation: None.

Guess the output #5

#include <stdio.h>

static int foo = 20;
static int foo = 10;

int main()
{
	printf("foo: %d\n", foo);

	return 0;
}

Compiling this code produces following output. click on below icon to see the output.

static_5.c:4:12: error: redefinition of ‘foo’
    4 | static int foo = 10;
      |            ^~~
static_5.c:3:12: note: previous definition of ‘foo’ with type ‘int’
    3 | static int foo = 20;
      |            ^~~

Explanation: None.

C Programming