I have an arduino code here and I am fairly new with the cod

I have an arduino code here and I am fairly new with the code. what is the 20ms delay before the digital read accomplishing?

void loop() {

// put your main code here, to run repeatedly:

if (digitalRead(sw) == LOW)

{

delay(20);

if(digitalRead(sw) == LOW)

{

    if((counter >=3) && (counter <=6))

    {

      digitalWrite(counter, HIGH);

      delay(500);

    }

    else if((counter >=7) && (counter <=10))

    {

      digitalWrite(counter-4, LOW);

      delay(500);

    }

    counter++;

}

}

if(counter > 10)

{

counter = 3;

digitalWrite(3 ,LOW);

digitalWrite(4 ,LOW);

digitalWrite(5 ,LOW);

digitalWrite(6 ,LOW);

}

}

Solution

When you are reading digital input lets, suppose from a switch, so you pressed the switch and a phenomenon is happen that called contact bounce. That means when a button is pressed the signal that is going to input is very noisy for a few millisecond. We will not able to notice it because its is too fast for us to notice. But a microcontroller could able to see it happening because the loop() function will have run several times during this brief period of bouncing. A very best way to get away with it is to use a delay() to put the Arduino to sleep during the bouncing period and have it wake up when the button will stable. I think 20ms delay is enough for your buttons.