while statement is an iteration structure that executes a set of code only when the condition is true. It is also known as "Entry controlled loop" since it is executed only inside the loop if the condition is satisfied. It ends with a ";" after the closing braces.

   while(condition) statement;

  #include <iostream.h>
  void main()
   {
   	int n;
      cout << "Enter a number > 0::";
      cin >> n;
      while(n>0)
       {
      	cout <<"Decremented value is::"<< n <<'\n';
      	n--;
       };
     cout << "Enter a valid number" <<'\n';
   } 

   Enter a number > 0::3
   Decremented value is::3 
   Decremented value is::2
   Decremented value is::1

In the above example, the entry controlled "while" function is used to decrement value of an integer.