Thank You PaulS.
Arduino has 2 pins: 0 and 1, which used to download a program.
Can we use them as extra I/O if we don't use serial communication at the run?
You could, but it's not suggested. Just for the fact that you'll generally need to use them sooner or later for some sort of debug.
You can always use analoginput pins just the same as digital pins! Just need to address them as 14-19 instead. (analog 0 = 14, analog 5 = 19), so to blink an LED on analogpin 0:
const byte ledPin = 14;
void setup()
{
pinMode(ledPin, OUTPUT);
}
void loop()
}
digitalWrite(ledPin, HIGH);
delay(1000);
digitalWrite(ledPin, LOW);
delay(1000);
}