Question

Header file guards are preprocessor directives whose primary role is to cause the compiler to _____?

1) Include the header file multiple times
2) Skip the compilation of the header file
3) Include the header file only once
4) Ignore the header file completely

Answer 1

Header file guards are preprocessor directives that ensure a header file is included only once in a single translation unit to avoid multiple definition errors.

Step-by-step explanation:

Header file guards are preprocessor directives whose primary role is to prevent multiple inclusions of the same header file in a single translation unit. This is important because including a header file more than once can lead to errors such as multiple definition errors. The correct choice is option 3: to Include the header file only once.

These guards work by checking if a unique identifier (often a macro) is defined before including the header. If it is not defined, the header file's contents are included and the identifier is defined. If the macro is already defined, it means the header has been included before, and the preprocessor will not include it again.

An example of header file guards would be:

#ifndef HEADER_FILE_NAME
#define HEADER_FILE_NAME
// Header file content here
#endif