Servo programming

Projects General Guidance
10 
#include <Servo.h>

Servo myservo;

byte leftPin = 8;
byte servoPin = 13;

byte switchValue = LOW;
int servoStep = 1; // int because we need negative values

byte pos = 90;  // servo initial position
byte delayPeriod = 20;

void setup() {

  myservo.attach (13);
  pinMode(leftPin, INPUT_PULLUP);
  pinMode(servoPin, OUTPUT);
}  

void loop() {
  readSwitch();
  updatePosition();
  moveServo();
}

void readSwitch() {

  if(digitalRead(leftPin) == HIGH) { // unpressed button will be HIGH
    switchValue = LOW;
  }
  else {
    switchValue = HIGH;
  }
}  
  
void updatePosition() {  

  if (switchValue == LOW) {
    pos = pos + servoStep;
  }
  
  if( pos < 20) { // some servos can't go all the way from 0 to 180
                  //   adjust to suit your servo
      pos = 20;
      servoStep = 1;
  }

  if( pos > 160) {
      pos = 160;
      servoStep = -1;
  }
}

void moveServo() {
    myservo.write(pos);
    delay(delayPeriod);
}

hey i changed it and it works thanks !!!