C++

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volatile

The volatile qualifier indicates that the variable it is applied to can be modified by an external entity (a hardware device for example). In this way the compiler is made aware that no optimization can take place to avoid checking the variable’s value. volatile can also be applied in conjunction with const, because also a const value can be modified by an external entity.

Example


#include <iostream>
using namespace std;

int main()
{   
     // both variables can be changed by an external entity
    volatile a = 5;
    const volatile b = 6;
}