Thread: Doubt regarding storage of a static variable

Hi frnds.. please help me in solving my doubt

In the below prog

Code:

#include.......
static int x = 10;

main()
{
    fun1();
    sleep(1);
     fun1();
     fun2();
}

fun1(){
  static int x = 11;
  printf("%d \n", x++ );
}

fun2()
{
  printf( "%d \n", x );
}

we have static var x globally initialized, and the static var with same name x is defined and modified with block scope in fun1 and the static var x being used in fun2.

Actually static variables will be stored in BSS (if uninitialized) and in Data seg (if initialized). But in the above prog where the locally defined static var x in fun1 is stored?

Thanks a lot for your answer. Conceptually.... yes the scope varies.. so, static var in fun1() will be stored in Data Segment with the block scope .... and even the global var x will also be stored in Data segment but with file scope. If so, when x is getting incremented in fun1() technically how the program will know which x should get incremented?

Frnds.... help needed

Originally Posted by karthik537

Thanks a lot for your answer. Conceptually.... yes the scope varies.. so, static var in fun1() will be stored in Data Segment with the block scope .... and even the global var x will also be stored in Data segment but with file scope. If so, when x is getting incremented in fun1() technically how the program will know which x should get incremented?

Both x's will be stored in the data segment, but that's their storage class and is very different from their scope.

The C lang isn't block structured except when it comes to variables and any variable defined in a block masks out a same name variable outside that block. So, the x in fun1() masks out the global x, only when fun1() is entered, elsewhere the global x has visibility.

The keyword 'static' means something totally different when used with global variables vs. inside a function.
When used on a global variable it means that the variable is only visible inside this source module. It will not interfere with any global variables of same name in other source modules.
When used on a variable inside a function it means that the value of the variable will remain. That is, re-entering the function will find the value is still there. Basically it ensures it is not on that stack but is instead in stable data space.

As itCbitC stated, type of physical memory used is less important than variable accessibility regarding C scoping rules.

Your question: "... technically how the program will know which x should get incremented?" is answered by realizing that the compiler generates memory access instructions according to the context in which it finds the variables. When inside a function, references to variables defined therein are made to wherever they are physically stored. The compiler is not confused just because the variable's name is also found elsewhere in the program.