What does the `#include` directive do in a C program?

What does the `#include` directive do in a C program?

• A. It starts a comment block
• B. It includes the contents of a specified file, typically a library
• C. It declares a new variable
• D. It ends the program execution

Answer: (B)

The `#include` directive in a C program is used to include the contents of a specified file, commonly a header file or a library, into the program. This allows the program to access functions, macros, and type definitions that are defined in the included file. By including these files, a programmer can utilize standard libraries, such as `stdio.h` for input and output functions or `stdlib.h` for general utilities, which are essential for writing functional code without having to redefine commonly used functionalities. When a C program is compiled, the preprocessor processes the `#include` directives and replaces them with the actual content of the included files. This feature promotes code reusability and modular programming, as developers can leverage existing libraries and avoid redundancy. Other options pertain to unrelated concepts; one mentions comment blocks, which are not connected to the inclusion of files. Another choice references variable declarations, which involve defining storage for data rather than including external code. The last option erroneously suggests ending program execution; however, the `#include` directive is not involved in controlling program flow or termination.

The #include directive in a C program is used to include the contents of a specified file, commonly a header file or a library, into the program. This allows the program to access functions, macros, and type definitions that are defined in the included file. By including these files, a programmer can utilize standard libraries, such as stdio.h for input and output functions or stdlib.h for general utilities, which are essential for writing functional code without having to redefine commonly used functionalities.

When a C program is compiled, the preprocessor processes the #include directives and replaces them with the actual content of the included files. This feature promotes code reusability and modular programming, as developers can leverage existing libraries and avoid redundancy.

Other options pertain to unrelated concepts; one mentions comment blocks, which are not connected to the inclusion of files. Another choice references variable declarations, which involve defining storage for data rather than including external code. The last option erroneously suggests ending program execution; however, the #include directive is not involved in controlling program flow or termination.