Code for Interfacing a Reed Switch with Arduino.

Arduino_Reed_Switch_Interface.ino

const int reedPin = 2;
const int ledPin = 12;
bool switchState = HIGH;

void setup() 
{
  Serial.begin(9600);
  pinMode(reedPin, INPUT);
  pinMode(ledPin, OUTPUT);
  digitalWrite(ledPin, LOW);
}

void loop() 
{
 switchState = digitalRead(reedPin);
 if (switchState == LOW) 
  {
    digitalWrite(ledPin, HIGH);
    Serial.println("Reed Switch is Closed. LED is ON");
  } 
 else
  {
   digitalWrite(ledPin, LOW);
   Serial.println("Reed Switch is Open. LED is OFF");
  } 
}