code:

int alcPin=5, 
    firstBarPin=2, 
    lastBarPin=11;

void setup() {
  for(int i=firstBarPin; i<=lastBarPin; i++) {
    pinMode(i, OUTPUT);
  }
}

void loop() {
  int i,
      alcReading = analogRead(alcPin),
      nBars = (lastBarPin-firstBarPin+1)*alcReading/1024;
  for(i=lastBarPin; i>=lastBarPin-nBars; i--) {
    digitalWrite(i, HIGH);
  }
  for(i=lastBarPin-nBars; i>=firstBarPin; i--) {
    digitalWrite(i, LOW);
  }
  delay(250);
}