assignmentLib.ino

// Include Light Sensor library
#include "light.h"

int sensorPin;

void setup() {
  // Set sensor pin
  sensorPin = 0;
}

void loop() {
  // Create instance of sensor lib
  Light mySensor(sensorPin);

  // Run, start sensing method
  mySensor.senseLight();
}

light.cpp

// Include header file
#include "light.h"

Light::Light(int pin) {
  Serial.begin(9600);
  _pin = pin;
}

void Light::senseLight() {
  lightLevel = analogRead(lightSensor);
  Serial.println(lightLevel);
}

light.h

#ifndef Light_h
#define Light_h

class Light {
  public:
    Light(int level);
    void senseLight();
  private:
    int _lightLevel;
    int _pin;
};

#endif