#include <Servo.h>

Servo servoControl;
int servoPosition;

void setup() {
  servoControl.attach(9);//setup PWM pin 9 on the arduino board to control servo motor
  // put your setup code here, to run once:

}

void loop() {
  for (servoPosition = 0; servoPosition <= 180; servoPosition += 20) //rotate the servo from 0-180 degrees in increment of 20 degree
  {
    servoControl.write(servoPosition); //Writes a value to the servo thus control a shaft position between 0-180 degrees as per the loop values.
    delay(500);                         //delays the rotate by 500ms.
  }
  
  for (servoPosition = 180; servoPosition >= 0; servoPosition -= 20) //rotates the servo back from 180-0 degrees in decrement of 20 degree
  {
    servoControl.write(servoPosition); //Writes a value to the servo thus controlling a shaft position between 180-0 degrees as per the loop values.
    delay(500);                         //delays the rotate by 500ms.
  }
  // put your main code here, to run repeatedly:

}