#include <Servo.h>
Servo servo;//create servo object toControl 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
}
void loop() {
  for (pos=0;pos<=180;pos+=1){//rotate from 0 dgrees
  // in steps of 1 dgrees
  servo.write(pos);      //tell servo to go to postion in variable 'pos' 
  delay(10);             //waits 10ms for the servo to reach to reach the position
  }
  for (pos=180;pos>=0;pos-=1){// rote from 180 degree to 0 degrees 
  servo.write(pos); //tellservo to go to position in variable 'pos'}
  delay(10);           //waits10ms for the servo to reach the postio
  }
  }