What is the difference between static int a and int a? [duplicate]

Question

Possible Duplicate:
Difference between 'global' and 'static global'

What is the difference between statements 1 and 2 :-

#include <stdio.h>
//In the global declaration area 

static int a; // 1.
int b;        // 2.

Thanks for help.

Answer 1

A static global variable is local to the translation unit it is defined in. So, if you define static int a; in two different translation units, this will create two independent variables. If you define a non-static global variable int b; in two translation units, you will experience a linker error (but you can use extern int b; in one of the two translation units to tell the linker that it should use the global variable from the other translation unit).

Answer 2

static int a; 
int b; 

a has internal linkage. b has extern linkage.

C99 6.2.2

6.2.2 Linkages of identifiers

• 1) An identifier declared in different scopes or in the same scope more than once can be made to refer to the same object or function by a process called linkage. There are three kinds of linkage: external, internal, and none.

• 2) In the set of translation units and libraries that constitutes an entire program, each declaration of a particular identifier with external linkage denotes the same object or function. Within one translation unit, each declaration of an identifier with internal linkage denotes the same object or function. Each declaration of an identifier with no linkage denotes a unique entity.

• 3) If the declaration of a file scope identifier for an object or a function contains the storage- class specifier static, the identifier has internal linkage.