Volatile in dos application

I have searched the forum and found that volatile keyword is used so that other programs are allowed to modify it.

Then why is it provided in dos programming which does not support multiprogramming concept.

Second question what is use of

Code:

const volatile int i;

Originally Posted by vaibhav

I have searched the forum and found that volatile keyword is used so that other programs are allowed to modify it.

That's probably not what you read.

Originally Posted by vaibhav

Then why is it provided in dos programming which does not support multiprogramming concept.

DOS had interrupts.

volatile is used when something outside of your code can modify the variable.

And a const volatile variable is one that your code can't change, but something else can -- like a processor register or some such.

Actually what volatile does is more like forces the compiler to allocate ordinary memory for a variable and to assume nothing when working with the variable. const volatile is really only used for cute little examples in programming forms.

for example

Code:

        const int i = 6;
	const_cast<int &>(i)=9;
	std::cout << "i=" << i << std::endl;

is allowed to output "i=6" as the const has told the compiler that it can assume that there will be a 6 wherever "i" appears.

Code:

	const volatile int i = 6;
	const_cast<int &>(i)=9;
	std::cout << "i=" << i << std::endl;

is requred to output "i=9"