Static and register storage class in C programming

   Static variables in C Language

Occasionally it is desirable to declare a variable within a function whose value will be stored throughout the execution of the program. If we declare a variable within a function ( auto ) then the variable is allocated and de-allocated each time the function is invoked. But if we declare a static variable within a function then when the function is exited , the variable retains its value.

#include<stdio.h>

void count(int , int);

void main()

{

int num1,num2;

clrscr();

printf("Enter two numbers:-");

scanf("%d%d",&num1,&num2);

count(num1,num2);

printf("Another two numbers:-");

scanf("%d%d",&num1,&num2);

count(num1,num2);

printf("%d",c);

getch();

}

void count(int a,int b)

{

static int c;

a=a+b;

c++;

printf("Sum is :-%d",a);

printf("\nYou have send %d pair of values.",c);

}

 use of static variable in C Language

#include <stdio.h>

int Static( );

int Dynamic( );

static int count = 0;

void main()

{

   int i;

   clrscr();

   printf("\nProgram for use of static variable in function\n");

   printf("count is %d\n",count);

   for (i=0; i<9; i++)

   {

      count ++;

      printf("count = %d, static count = %d, dynamic count = %d\n",count, Static(), Dynamic());

   }

   getch();

}

int Static( )

{

   static int i = 0;  

   return( ++i );

}

int Dynamic(  )

{

   int i = 0; 

   return( ++i );

}

Register variable

Registers are special storage areas within a computers CPU.The actual Arithmetic and Logical operations are done within Registers and these operations are carried out by transferring datas from computers memory to registers , the indicated operations are carried out and then datas are transferred to memory. This process is executed several times in a program execution.

For programs the execution time can be reduced  if we store certain values within register rather than memory. In C a variable can be assigned this storage class simply by preceding the type declaration with the keyword register. Register variables are closely related to auto variables , except address operator ( & ) cannot be applied on them.

Any Question ? Please put your comments....