Constants and Volatile

Constants

Things which are all unchangable are said to be constant whereas things which are all changable are said to be volatile. The following diagram clearly represents the relationship between constant and volatile.

In the following diagram sealed box contains a variable i which is initialized by 16 at the time of declaration which indicates that one cannot change the value of variable i after initialization whereas opened box contains a varibale j which is intialized by 30 at the time of declaration, open box indicates the one can change the value of variable j at anytime.

Constant vs Volatile

The following table represents the constant against volatile

Constant Program Using Keyword

Let's write a C program to demonstrate the purpose of constant variable

#include <stdio.h>
int main()
{
const int i = 16;
i = i + 1;
printf("The value of i = %d ",i);
return 0;
}

Constant Program Without Using Keyword

Let's write a C program to demonstrate the purpose of constant variable without using keyword.

#include <stdio.h>
#define i 16
int main()
{
printf("The value of i = %d ",i);
return 0;
}

Volatile Program Using Keyword

Let's write a C program to demonstrate the purpose of volatile variable

#include <stdio.h>
int main()
{
volatile int j = 1;
j = j + 1;
printf("The value of j = %d ",j);
return 0;
}

Volatile Program Without Using Keyword

Let's write a C program to demonstrate the purpose of volatile variable

#include <stdio.h>
int main()
{
int j = 1;
j = j + 1;
printf("The value of j = %d ",j);
return 0;
}

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