C Programming - Declarations and Initializations - Discussion

@ALL.

extern is keyword .

When we use this word before the variable then that will store in the stack.
extern int a;
main()
{
-----
-----
}

In above program, I declared but not assigned so "a" value may present in other programs then you will get that value by using extern without this we can not get it.

The same way when function declares with extern we can get from other programs. But our compiler assumes that if you do not mention extern (in function concept only) it treats as extern.

I am not understanding this, please explain it for me.

Extern is a data storage type or storage class.
extern is a global variable.
Scope of the global variable is global.

Eg:-
file1.c

include "file2.c"
main()
{
extern int a;
printf(",,...d",a);
}


file2.c

int a;

extern points to the int a of file2.c(another file) .
Because file1.c refers to file2.c (#include "file2.c" )

What is the difference between int main and extern int main?

"Extern" is keyword in C ,suppose you write 2 diff. function in diff. file and main function in third file,

And you want one variable use globally eg. int a;

At that time we use extern keyword eg. extern int a;

This procedure same for function.

Hi,

How is extern function different from normal function?

If a function is declared as extern, then that function can be overrided?

What is global function and why extern keyword used to declare a function?

extern int a;

extern keyword tell the compiler, identifier a of type integer define anywhere through the program. This statement is just declaration.

@Ragveni.

Global variable means that the variable which are defined outside all the blocks of functions, anywhere in file (not only before main).

main()
{
pf("hello");
}
int a;

a is global variable.

Declaration means that the variable exist in program :-

#include<stdio.h>
main()
{
int a;
printf("%d",&a);
return 0;
}
Why it gives address of memory location?