Why some C files are in red (indicates that an error has been occure)?
You're using unlicensed features. Presumably an Eval or Lite version of Keil.
how to install a licensed version?
When you buy the licence, you will get instructions with it!
To buy a license, get in touch with your local distributor:http://www.keil.com/distis/You can also request a free of charge 30 days time limited MDK Pro license for the purpose of evaluation.
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