code 3-3 in black book

const int BLED= 9 ;
const int Light= 0 ;
const int Minlight = 400 ;
const int Maxlight = 850 ;
int val= 0 ;
void setup ()
{
  pinMode (BLED, OUTPUT) ;
  pinMode (Light, INPUT) ;
  Serial.begin (9600) ;
}
void loop ()
{
  val = analogRead(Light) ;
  Serial.print(val);
  Serial.print("              ");
  delay(50);
  val = map(val, Minlight, Maxlight, 255, 0) ;
  val = constrain(val, 0, 255) ;
  Serial.println(val);
  analogWrite (BLED, val) ;
}