#include 

Servo myservo;
// It creates a servo object, which is used to control the servo

int potentioPIN = A0;  // specified analog pin used to connect the potentiometer
int value;    // value initialized to the variable to read the value from the analog pin

void setup() 
{
  myservo.attach(9);  // servo connected to pin 9 of the Arduino board to the servo object
}

void loop() 
{
  value = analogRead(potentioPIN);            
  // reads the value of the potentiometer (value between 0 and 1023)
  value = map(value, 0, 1023, 0, 180);     
  // scale it to use it with the servo (value between 0 and 180)
  myservo.write(value); 
  delay(1000); // it will wait for 1 second for the 
  // It will set the position of the motor according to the scaled value
  value = map(value, 1023, 0, 180, 0);
  // reads the value of the potentiometer (value between 1023 and 0)
   myservo.write(value);
  // scale it to use it with the servo (value between 180 and 0)
  // the motor will rotate in reverse direction
  delay(1000);                           
  // delay time in milliseconds
  //after 1500 millisecond it will again rotate from 0 to 180 degree
}