How to write a program that produces calculation results after a certain time interval with the ability to change parameters?

Question

Programming

Let's say there is a variable a and b. At each calculation step, we add the value of variable b to variable a. It is necessary that the program displays the value of each step with an interval of 1 second. But at the same time, it should be possible to change the variable b during the calculation. That is, you can pause, change the value of the variable and continue counting with the new value. I think that you can put some kind of pause button that will change the value of the flag in a loop

переменные a, b
flag1 = true (кнопка)

цикл с интервалом по времени:
   a = a + b
   считать значение falg1 (нажал ли кнопку паузы)
   если flag1 = false: (нажал)
      считать b
      flag1 = true
      продолжить
   вывод переменной a

How to implement this count and output with a certain time interval with the possibility of a pause and a change in the value of the variable? And yes, I would like to write in C ++
windows, if that

Answer 1

Nothing to pause

#include <iostream>
#include <windows.h>
using namespace std;

int main()
{
  int val =0, timer = 0, freq = 50;

  while(true) {
    Sleep(1000/freq); //win-функция
    timer += 1000/freq;

    if (timer > 1000) {
      timer -= 1000;
      cout << val++ << endl;
    }

    if (GetAsyncKeyState(VK_SPACE)) { //win-функция
      cout << "New val: ";
      cin >> val;
    }
  }

  system("pause");
  return 0;
}

Answer 2

should be around that. If you hold down the "C" button while the program is running, you will need to enter a new value for the variable b.

while(true){
if(getch() == 32){
std::cout << 'Vvedite novoe b: '; std::cin >> b;
}
std::cout << a << std::endl;
a = a + b;
usleep(1000000);
}