Multiple choice

Which one of the following is true for identifiers that begin with an underscore?

  1. They are generally treated differently by preprocessors and compilers from other identifiers.

  2. They are case-insensitive.

  3. They are reserved for usage by standards committees, system implementers, and compiler engineers.

  4. Applications programmers are encouraged to employ them in their own code in order to mark certain symbols for internal usage.

  5. They are deprecated by Standard C and are permitted only for backward compatibility with older C libraries.
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C Correct answer
Explanation

In the C programming language, identifiers beginning with an underscore followed by an uppercase letter or another underscore, as well as identifiers beginning with an underscore in the global scope, are reserved for use by the implementation, standard libraries, and compiler vendors to prevent naming collisions.

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