C : Volatile Modifier

Hello, friends. I am the student of the MscCS. I have the knowledge of the C language. But I don't know about the Volatile Modifier of the C language. I have to submit the assignment in the college. So, I want know about the Volatile Modifier of the C language. I would also like to know about how the Volatile Modifier work, what is the use of the Volatile Modifier, how can I use them in the program. So, Can anyone help me to know about the Volatile Modifier.

Hi, The Volatile Modifier means it is a directive to the compiler's optimizer. The operations involving Volatile Modifier should not be optimized in certain ways. It is worth to having use of the Volatile Modifier in two special cases. In the first case, It involves memory-mapped hardware means a device like a graphics adapter as if it is part of the computer's memory that appears to the computer's hardware and In the second case, It involves shared memory means that memory that is being used by more than two programs simultaneously running.

I suggest you to carefully go through the following lines of code that help you to know about the Volatile Modifier more easily :
tim_t tim_add(volatile const struct timr *t, int b)
{
int m;
int y;
tim_t then;
y = 0;
then = t->value;
for (m = 0; m < 1000; m++)
{
y = y + b;
}
return t->value - then;
}

When the value of the variable can change unexpectedly that time variable can be declared as Volatile. basically, Only three types of variables can change:
1. Global variables accessed by multiple tasks within a multi-threaded application
2. Memory-mapped peripheral registers
3. Global variables modified by an interrupt service routine

Note that you can not be allowed to use volatile modifier on any time. The following are the data types with those you can use Volatile Modifier :
1. An enum type with an enum base type of the following: uint, sbyte, sshort, byte, short, int.
2. byte, sbyte, ushort, short, uint, int, float, char, bool.
3. Any pointer type in a unsafe context.
4. Any reference type.
Example of Volatile Modifier :
public volatile int age;