/* Program 2-8 Reading SW and use it to control the LED.
  */
const int LED = 13; /* LED internally connected*/
const int SW1 = 3;  /* use pin 3 for SW1 externally connected */

void setup()
{
    /* configure input output pins for switch and LED */
    pinMode(LED, OUTPUT);
    pinMode(SW1, INPUT);
}
void loop()
{
    /* read switch and use the value to set LED */
    digitalWrite(LED, !digitalRead(SW1));
}