Check the built-in LED using Arduino IDE

/* Various Data type */

void setup() {
  Serial.begin(115200);

  Serial.println("Hello World");
  Serial.println(78);
  Serial.println(1.23456);
  Serial.println('N');

}

void loop() {
  

}

/* Various Number */

void setup() {
  Serial.begin(115200);

  Serial.println(78, DEC);
  Serial.println(78, HEX);
  Serial.println(78, BIN);

  Serial.println(1.23456, 0);
  Serial.println(1.23456, 2);
  Serial.println(1.23456, 4);

}

void loop() {
  
}

/* Turn on the LED */

const int LED = 13;

void setup() {
  pinMode(LED, OUTPUT);

  digitalWrite(LED, HIGH);

}

void loop() {
  

}

/* Turn off the LED */

const int LED = 13;

void setup() {
  pinMode(LED, OUTPUT);

  digitalWrite(LED, LOW);

}

void loop() {
  

}

/* Blinking the LED once*/

const int LED = 13;

void setup() {
  pinMode(LED, OUTPUT);

}

void loop() {
  digitalWrite(LED, HIGH);
  digitalWrite(LED, LOW);

}

/* Check Blinking the LED*/

const int LED = 13;

void setup() {
  pinMode(LED, OUTPUT);

}

void loop() {
  digitalWrite(LED, HIGH);
  delay(500);
  digitalWrite(LED, LOW);
  delay(500);

}

/* Reduce the LED blink interval */

const int LED = 13;

void setup() {
  pinMode(LED, OUTPUT);

}

void loop() {
  digitalWrite(LED, HIGH);
  delay(50);
  digitalWrite(LED, LOW);
  delay(50);

}

/* Feel the gap between the flashing LED */

const int LED = 13;

void setup() {
  pinMode(LED, OUTPUT);

}

void loop() {
  digitalWrite(LED, HIGH);
  delay(5);
  digitalWrite(LED, LOW);
  delay(5);

}

/* Make a faint LED */

const int LED = 13;

void setup() {
  pinMode(LED, OUTPUT);

}

void loop() {
  digitalWrite(LED, HIGH);
  delay(1);
  digitalWrite(LED, LOW);
  delay(9);

}

/* Make a bright LED */

const int LED = 13;

void setup() {
  pinMode(LED, OUTPUT);

}

void loop() {
  digitalWrite(LED, HIGH);
  delay(9);
  digitalWrite(LED, LOW);
  delay(1);

}

/* Adjust the LED brightness */

// Adjust LED brightness level 11 at 0.01 second intervals
const int LED = 13;

void setup() {
  pinMode(LED, OUTPUT);

}

void loop() {
  int i;
  for (i = 0; i <= 10; i++){
    digitalWrite(LED, HIGH);
    delay(i);
    digitalWrite(LED, LOW);
    delay(10-i);
  }

}

/* Adjust the LED brightness */

// Adjust LED brightness level 11 at 0.1 second intervals
const int LED = 13;

void setup() {
  pinMode(LED, OUTPUT);

}

void loop() {
  int i;
  int cnt;
  for (i = 0; i <=10; i++){
    while(true){
      digitalWrite(LED, HIGH);
      delay(i);
      digitalWrite(LED, LOW);
      delay(10-i);

      cnt++;
      if(cnt == 10) break;
    }
  }

}