#include <Servo.h>
 Servo servo; // create servo object to control a servo
  int pos =0; //variable to store the servo position 
 void setup() {
  
  servo.attach(9); //attaches the servo on pin 9 to the servo object 
  // put your setup code here, to run once:

}

void loop() 
   {
   for( pos =0;pos<=180;pos+=1)
  {//rotate from 0 degrees to 180 degrees//in steps of 1 degrees 
  servo.write(pos) ; //tell servo to go to position in variable 'pos'
  delay(10);
  //waits 10ms for the servo to reach the position 
  }
  for( pos =180;pos>=0;pos-=1)
  {//rotate from 180 degrees to 0 degrees 
  servo.write (pos);//tell servo to go to position in variable 'pos'
  delay(10);//waits 10ms for the servo to reach the position
  }
  // put your main code here, to run repeatedly:

}