Why Are Header Guards Essential for Preventing Multiple Inclusions in C ?

Implementing Header Guards

Header guards are crucial for preventing multiple inclusions of the same header file. They typically consist of three directives:

• #ifndef FILENAME_H: Checks if the filename (with an appended _H) has not been defined yet.
• #define FILENAME_H: Defines the filename as a macro to prevent further redefinitions.
• #endif: Ends the conditional directive.

Declarations within Header Guards

Anything between #ifndef and #endif will not be compiled if the header guard has already been defined. This includes declarations, such as:

#ifndef ADD_H
#define ADD_H

#include "mymath.h"
int add(int x, int y);

#endif

Convention of Appending _H

Appending _H to the filename is a widely accepted convention. While it is not a strict requirement, it provides an easy way to differentiate header guard macros from other macros. However, you can use any unique identifier as the header guard.

int main() Placement

The int main() function should not be placed within a header file. It should always be present in a .cpp file, separate from the header files it includes.

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