Some simple Arduino LED blink cpp code.

blink.cpp

#include <Arduino.h>

void setup()
{
    // put your setup code here, to run once:
    pinMode(LED_BUILTIN, OUTPUT);
}

void loop()
{
    // put your main code here, to run repeatedly:
    digitalWrite(LED_BUILTIN, HIGH);
    delay(300);
    digitalWrite(LED_BUILTIN, LOW);
    delay(300);
}