C Preprocessors Tutorial

1. #define Directive

The #define directive is used to define constants or macros. It allows you to give a name to a constant or piece of code:

#define PI 3.14159

Example:

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#include <stdio.h>
#define PI 3.14159

int main() {
    printf("The value of PI is: %f\\n", PI);
    return 0;
}

2. #include Directive

The #include directive is used to include external files, such as standard libraries or user-defined header files:

#include 

Example:

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#include <stdio.h>

int main() {
    printf("Hello, World!\\n");
    return 0;
}

3. Conditional Compilation (#ifdef, #endif)

The #ifdef directive is used for conditional compilation. This allows you to compile code only if a specific condition is met:

#ifdef DEBUG
    printf("Debugging mode enabled\\n");
#endif

Example:

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#include <stdio.h>
#define DEBUG 1

int main() {
    #ifdef DEBUG
        printf("Debugging mode enabled\\n");
    #endif
    return 0;
}

4. Conclusion

C preprocessors help manage code, enable conditional compilation, and allow for easier code maintenance. By using directives like #define, #include, and #ifdef, you can improve your code's structure and flexibility.