Ex 4.2

// Example 4.2
void setup()
{
	pinMode(8, OUTPUT); // speker on pin 8
}

	int del = 250; // for tone length
	int lowrange = 2000; // the lowest frequency value to use
	int highrange = 4000; //  the highest...
void loop()
{
	// increasing tone
	for (int a = lowrange; a<=highrange; a++)
	{
		tone (8, a, del);
	}
	// decreasing tone
	for (int a = highrange; a>=lowrange; a--)
	{
		tone (8, a, del);
	}
}