Arduino code and video for 4 keys keypad Robojax.com

This is the Arduino code for 4 keys keypad

This video shows you how to use 4 key keypad for arduino. http://robojax.com/learn/arduino/

 /*
 * This is the Arduino code for 4 keys Keypad.
 * watch the video for details and demo https://youtu.be/BiOh_Z2N7kk
 *  * 
 * Written by Ahmad Nejrabi for Robojax Video channel www.Robojax.com
 * Date: Dec 28, 2017, in Ajax, Ontario, Canada
 * Permission granted to share this code given that this
 * note is kept with the code.
 * Disclaimer: this code is "AS IS" and for educational purpose only.
 * this code has been downloaded from http://robojax.com/learn/arduino/
// Recorded Dec 28, 2017 for Robojax.com

#define key1 2 //connect wire 1 to pin 2
#define key2 3 //connect wire 2 to pin 3
#define key3 4 //connect wire 3 to pin 4
#define key4 5 //connect wire 4 to pin 5

void setup() {
 Serial.begin(9600);
 pinMode(key1, INPUT_PULLUP);// set pin as input
 pinMode(key2, INPUT_PULLUP);// set pin as input
 pinMode(key3, INPUT_PULLUP);// set pin as input
 pinMode(key4, INPUT_PULLUP);// set pin as input   
}

void loop() {
  int key1S = digitalRead(key1);// read if key1 is pressed
  int key2S = digitalRead(key2);// read if key1 is pressed
  int key3S = digitalRead(key3);// read if key1 is pressed
  int key4S = digitalRead(key4);// read if key1 is pressed 
 // Code written for Robojax.com video Tutorial
     if(!key1S){
      Serial.println("key 1 is pressed");
     }
     if(!key2S){
      Serial.println("key 2 is pressed");
     }
     if(!key3S){
      Serial.println("key 3 is pressed");
     }
     if(!key4S){
      Serial.println("key 4 is pressed");
     }          
     delay(100);
}