pull-down resistor

what is pull-down resistor do? Arduino Project book (170 pages) , chapter 02.

nish1013:
what is pull-down resistor do? Arduino Project book (170 pages) , chapter 02.

It pulls down the input. That is it makes the input a logic zero in the absence of any other voltage input.
Inputs should never connected to nothing or they float and give random readings.

Many thanks for your reply.

Unfortunately this book seems like not giving this knowledge, it just state facts and move :zipper_mouth_face:

See this link for more information
http://www.thebox.myzen.co.uk/Tutorial/Inputs.html
There is a lot of other good stuf on my site as well.