C Preprocessor Directives in C Language

Categories: C language

The C preprocessor is a micro processor that is used by compiler to transform your code before compilation. It is called micro preprocessor because it allows us to add macros.


Let's see a list of preprocessor directives.


#include

#define

#undef

#ifdef

#ifndef

#if

#else

#elif

#endif

#error

#pragma


What is C Macros

A macro is a segment of code which is replaced by the value of macro. Macro is defined by #define directive. There are two types of macros:


1. Object-like Macros

2. Function-like Macros


1. Object-like Macros

The object-like macro is an identifier that is replaced by value. It is widely used to represent numeric constants. For example:


#define PI 3.14  

Here, PI is the macro name which will be replaced by the value 3.14.


2. Function-like Macros

The function-like macro looks like function call. For example:


#define MIN(a,b) ((a)<(b)?(a):(b))    

Here, MIN is the macro name.

Visit #define to see the full example of object-like and function-like macros.


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