An example Arudino code of charlieplexing. For details about charlieplexing, read this: http://en.wikipedia.org/wiki/Charlieplexing

charlieprexing3.ino

// referenced this code: http://www.instructables.com/id/Charlieplexed-Arduino-8x8-LED-Grid-Display-Shield-/step2/Code/
const int UPPERPIN = 13;
const int LOWERPIN = 11;

void setup() {
  resetAllPins();
}

void loop() {
  for(int i=LOWERPIN;i<=UPPERPIN;i++){
    for(int j=LOWERPIN;j<=UPPERPIN;j++){
      if (i == j) continue;

      pinMode(i, OUTPUT);
      pinMode(j, OUTPUT);
      digitalWrite(i, HIGH);
      digitalWrite(j, LOW);

      delay(1000);

      resetAllPins();
    }
  }
}

void resetAllPins(){
  for(int i=LOWERPIN;i<=UPPERPIN;i++){
    pinMode(i, INPUT);
  }
}