The #ifndef directive tests to see whether ________
Options
A. a class has been defined
B. a variable has been given a value
C. a class has no variable definitions
D. any objects of the class have been instantiated
Correct Answer
a class has been defined
Explanation
#ifndef checks whether the given token has been #defined earlier in the file or in an included file; if not, it includes the code between it and the closing #else or, if no #else is present, #endif statement. #ifndef is often used to make header files idempotent by defining a token once the file has been included and checking that the token was not set at the top of that file.
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