How to identify the file content as ASCII or binary

Question

How do you identify the file content as being in ASCII or binary using C++?

Answer 1

The contents of every file is binary. So, knowing nothing else, you can't be sure.

ASCII is a matter of interpretation. If you open a binary file in a text editor, you see what I mean.

Most binary files contain a fixed header (per type) you can look for, or you can take the file extension as a hint. You can look for byte order marks if you expect UTF-encoded files, but they are optional as well.

Unless you define your question more closely, there can't be a definitive answer.