Static Keyword ( C )

• Static Global variables: Variable is initialised only once and then it is reused. Variables can be used anywhere in the same file only. Scope is said to be the complete file, Lifetime is the complete program.

#include<stdio.h>

static int a;

int main(){

  printf("%d \n",a); // will print 0 


  return (0);
}        

• Static variables in Functions (including main function): Variable is initialised only once and then it is reused. Scope is said to be the Function in which it is initialised, Lifetime is the complete program.

#include<stdio.h>

void function(){
  static int b=0;
  b++;
  printf("%d, ",b); // will print 1, 2, 3, 

  c++; //ERROR: 'c' was not declared in this scope
  printf("%d, ",c); //ERROR: 'c' was not declared in this scope

}

int main(){

  for(int i=0 ; i<3 ; i++){
    function();
  }

  static int c=2;
  c++; 
  printf("%d, ",c); //will print 3, 

  return (0);

}        

• Static Functions : Functions cannot be called from other files of the project.

// main.c

static func(){
  return (0) ;
}

int func_1(){
  return (10) ;
}

int main (){
  printf("%d \n", func() ); //will print 0 
  printf("%d \n", func_1() ); //will print 10
  printf("%d \n", func_2() ); // ERROR: Func_2() not declared in this scope. 
  printf("%d \n", func_3() ); // will print 20

  return (0);
}

        

let's say, another file is also a part of the same project.

//file_1.c

static int func_2(){
  return (10+func()); //ERROR: func() not declared in this scope.
}

int func_3(){
return (20);
}        

Miscellaneous implications:

• Static variables are stored in data segment.
• Static variables cannot be declared inside structure.