variable declation

In the following sketch why does the third line not assign to pin A0
int ledPin = 9; // LED connected to digital pin 9
int analogPin = 3; // potentiometer connected to analog pin 3
int val = 0; // variable to store the read value

void setup()
{
pinMode(ledPin, OUTPUT); // sets the pin as output
}

void loop()
{
val = analogRead(analogPin); // read the input pin
analogWrite(ledPin, val / 4); // analogRead values go from 0 to 1023, analogWrite values from 0 to 255
}

why does the third line not assign to pin A0

The third line seems to be declaring an integer variable "val". Nothing to do with any pins.

Try using "A0" instead of "3".