cout << "Machine ID: ";
	//WHILE LOOP: check whether Machine ID is in numeric
	while(!(cin >> machineID)){
		//display error message
		cout << "ERROR! Invalid Machine ID! Please try again..." << endl;
		cout << "Machine ID: ";
		
		cin.clear(); //clear previous user input
		cin.ignore(INT_MAX, '\n'); //discard previous user input
	}