static variables are those which retains the outcoming 
value after 'n' iterations(initialized once)

(see below)
#include <stdio.h>

int g = 10;  

main(){

    int i =0; 
    void f1();
    f1();            
    printf(" after first call \n");
    f1();            
    printf("after second call \n");
    f1();            
    printf("after third call \n");

}
void f1()
{
    static int k=0;  //static variable
    int j = 10;  //auto variable           
    printf("value of k %d j %d",k,j);
    k=k+10;
}


the output will be:

value of k 0 j 10 after first call
value of k 10 j 10after second call
value of k 20 j 10after third call

hope this will help u....

I have a doubt..what is the difference between.."static" 
and "constant(const)"??

enum

a static variable is shared by all the the instances of a
class.

Variables that statically retain their memeory location 
across function calls or in other words even beyond their 
scope. 

Global static values or functions are used to hide them 
from other files in the program.

Static vairiable is one which can be accessed without 
creation of an object of Class i.e. by direct calling calss.

static variables are variables that are initiated only once 
in a memory,suppose u have initiated a variable as static 
everytime u visit a iteration the value is changed 4m the 
initialised value,not like auto variables where the values 
remain same everytime u visit a iteration