/* Program 2-9 Reading SW2 and use it to control the LED.
  */
const int LED2 = 5; /* LED2 externally connected*/
const int SW2 = 3;  /* SW2 externally connected*/

void setup()
{
    /* configure input output pins for switch and LED */
    pinMode(LED2, OUTPUT);
    pinMode(SW2, INPUT);
}
void loop()
{
    /* read switch and use the value to set LED */
    digitalWrite(LED2, !digitalRead(SW2));
}