arduino.cc

boolean ledState = false;        
int lastButtonState = 0;

void setup() {
 pinMode(4, INPUT);
 pinMode(7, OUTPUT);
 Serial.begin(9600);
}

void loop() {
 
 int buttonState = digitalRead(4);
 
 if (lastButtonState != buttonState && buttonState == 1) {
   ledState = !ledState;
 }

lastButtonState = buttonState;
 
if (ledState) {
  digitalWrite(7,HIGH);
} else {
  digitalWrite(7,LOW);
}
  


}