//'Buffer'/'NOT' logical gate!
int G=7;
//Pins of the gate...
void setup(){pinMode(G, OUTPUT);}
void loop(){
  //HIGH - 'Buffer' & LOW - 'NOT'
  digitalWrite(G, 1);
  delay(500);
  //LOW - 'Buffer' & HIGH - 'NOT'
  digitalWrite(G, 0); 
  delay(500);
}