Practing with a book "Making Things Talk"

I am researching serial communication.

 Note: if you plan to do a practice page 41, you should be careful.

I highly recommend you to add a following cord to the void loop section of  the sample cord.

delay(10);

Otherwise Arduino program will scream. (if you have a single core CUP, your operating system will also scream) 

My laptop, which has a CPU Intel Core2DUO 2.4Gh, is not a  slow computer but one of CUP core was occupied by the Arduino program and the Arduino program responded very very slowly.