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# Pre-Processors

Preprocessors in C++ are directives that are processed before the actual compilation of your code begins. They allow you to perform certain operations on your source code before it's compiled. Here's a concise overview of preprocessors in C++:

1. Inclusion of header files:

   ```cpp
   #include <iostream>  // For standard library headers
   #include "myheader.h"  // For your own headers
   ```
2. Macro definitions:

   ```cpp
   #define PI 3.14159
   #define SQUARE(x) ((x) * (x))
   ```
3. Conditional compilation:

   ```cpp
   #ifdef DEBUG
     // Debug code
   #endif
   ```
4. File inclusion guards:

   ```cpp
   #ifndef MYHEADER_H
   #define MYHEADER_H
   // Header content
   #endif
   ```
5. Pragma directives:

   ```cpp
   #pragma once
   ```

These directives help with code organization, portability, and can sometimes improve performance.