4x4 Keypad with Arduino Tutorial

#include <Keypad.h>

int led_pin=13;
const byte ROWS = 4; //four rows
const byte COLS = 4; //four columns
//define the cymbols on the buttons of the keypads
char hexaKeys[ROWS][COLS] = {
{'1','2','3','A'},
{'4','5','6','B'},
{'7','8','9','C'},
{'*','0','#','D'}
};
byte rowPins[ROWS] = {2,3,4,5}; //connect to the row pinouts of the keypad
byte colPins[COLS] = {6,7,8,9}; //connect to the column pinouts of the keypad

//initialize an instance of class NewKeypad
Keypad customKeypad = Keypad( makeKeymap(hexaKeys), rowPins, colPins, ROWS, COLS);

void setup(){
pinMode(led_pin,OUTPUT);
Serial.begin(9600);
}

void loop(){
char customKey = customKeypad.getKey();

if (customKey){
digitalWrite(led_pin,HIGH);
Serial.println(customKey);
delay(100);
}
else digitalWrite(led_pin,LOW);
}