After reading this week's reading materials, I did Labs.
I already learn serial communication at the class of Prototyping Electronic Devices.
So that was good for my review of the class and previous study(when my undergrad and ex-graduate)
I learned how to see the values via serial port in Terminal app(actually I use iTerm and VSCode).
(I didn't connect any device in this time tho)
This link was good for understanding.
Carriage Return is actually not same as line feed code.
That command declare to go back a cursor to the head of line.
And CR was used in old-fashioned Mac.
That's why it is almost the same as line feed code.