Which of the following statements are true?

A$.$ All files are stored in binary format. So$,$ all files are essentially binary files.

B$.$ Text I$/$O is built upon binary I$/$O to provide a level of abstraction for character encoding and decoding.

C$.$ Encoding and decoding are automatically performed by text I$/$O$.$

D$.$ For binary input, you need to know exactly how data were written in order to read them in correct type and order.