Something strange happened when I opened Arduino IDE - it said it could not locate a default directory for my sketches and reset itself to a default. I changed it back to where I have all my codes. Now, no matter where I put the default directory of sketches, the whole text area is grayed out and I cannot type or modify code (but I can still open it).
I tried to google it to no avail. A lot of problems related to the serial port being grayed out.
Thank you very much in advance for help!