Preprocessor Directives

Understanding C Program Compilation Process

Introduction to Preprocessor (प्रीप्रोसेसर का परिचय)

Preprocessor C program को compile करने से पहले उस पर कुछ operations perform करता है। ये source code को modify करता है और compiler को modified code pass करता है।

The preprocessor performs certain operations on a C program before compilation. It modifies the source code and passes the modified code to the compiler.

Key Points (मुख्य बिंदु):

Preprocessor directives # से start होते हैं
Preprocessor directives start with #
Preprocessing compilation से पहले होता है
Preprocessing occurs before compilation
Preprocessor code को modify करता है
Preprocessor modifies the code

Source Code

Preprocessing

Compilation

Linking

Common Directives (कॉमन डायरेक्टिव्स)

Common preprocessor directives और उनका use:

Common preprocessor directives and their usage:

#include       // Include header file
#define PI 3.14159     // Define constant
#define MAX(a,b) ((a)>(b)?(a):(b))  // Define macro

#ifdef DEBUG           // Conditional compilation
    printf("Debug mode\n");
#endif

#pragma once          // Prevent multiple inclusion

Directive (डायरेक्टिव)	Description (विवरण)
#include	Header file को include करता है
#include	Includes a header file
#define	Constant या macro को define करता है
#define	Defines a constant or macro

Macros (मैक्रोस)

Macros और उनका implementation:

Macros and their implementation:

// Simple macro
#define SQUARE(x) ((x) * (x))

// Multi-line macro
#define PRINT_ARRAY(arr, size) \
    for(int i=0; i



                
                    Macro Features (मैक्रो फीचर्स):
                    
                        Stringizing operator (#) string बनाता है
                        Stringizing operator (#) creates a string
                        
                        Token pasting operator (##) tokens को join करता है
                        Token pasting operator (##) joins tokens
                        
                        Macros में parentheses का use important है
                        Parentheses are important in macros



            
                Conditional Compilation (कंडीशनल कंपाइलेशन)
                Conditional compilation directives:
                Conditional compilation directives:
                
                
                    #ifdef DEBUG
    // Debug code
    printf("Debug information\n");
#else
    // Release code
    printf("Release version\n");
#endif

#if VERSION > 2
    // New version features
#elif VERSION == 2
    // Version 2 features
#else
    // Old version features
#endif
                
            

            
                Best Practices (सर्वोत्तम प्रथाएं)
                Preprocessor directives के best practices:
                Best practices for preprocessor directives:
                
                
                    Macro Names: UPPERCASE में macro names use करें
                    Macro Names: Use UPPERCASE for macro names
                    
                    Parentheses: Macro definitions में parentheses का use करें
                    Parentheses: Use parentheses in macro definitions
                    
                    Header Guards: Header files में include guards use करें
                    Header Guards: Use include guards in header files
                    
                    Conditional Compilation: Debug और release versions के लिए use करें
                    Conditional Compilation: Use for debug and release versions