PREPROCESSOR

C PROGRAMMING CONTAINS VARIOUS ELEMENTS LIKE PREPROCESSOR DIRECTIVES , FUNCTIONS , DATA TYPES , OPERATORS , ETC .

WE SHALL DISCUSS HERE ABOUT ALL THE THINGS WHICH ARE RELATED TO C PROGRAMMING ONE BY ONE .

IN THIS POST  WE DISCUSS ABOUT PREPROCESSOR.

• WHAT IS PREPROCESSOR ?

AS ITS NAME IMPLIES , THE PROCESSOR WHICH ARE DEFINE BEFORE THE COMPILATION OF SOURCE CODE(PROGRAM) IS CALLED PREPROCESSOR . IN SIMPLE LANGUAGE ,  THOSE FUCNTIONS WHOSE MEANING HAD ALREADY DEFINED IN PROGRAMME BEFORE THE COMPILATION .

for example:- #include<stdio.h>
                               #include<conio.h>
                               #define   etc

NOTE:-  printf() and scanf() functions are the functions of #include<stdio.h>
               clrscr() and getch() functions are the functions of #include<conio.h>

1. PREPROCESSOR DIRECTIVES:-

                                                                   PREPROCESSOR DIRECTIVES FOLLOW SPECIAL SYNTAX THAT ARE BEGIN WITH THE SPECIAL SYMBOL (#) AT THE END.

THESE DIRECTIVES CAN BE DEVIDED INTO THREE CATEGORIES:-

• MACRO SUBSTITUTION DIRECTIVES
• FILE INCLUSION DIRECTIVES
• COMPILER CONTROL PROGRAMME

a.)MACRO SUBSTITUTION DIRECTIVES:-
                                                                       MACRO SUBSTITUTION IS A PROCESS WHERE AN IDENTIFIER IN A PROGRAM IS REPLACED BY PREDEFINED STRING WITH #define STATEMENT .

a.) SIMPLE MACRO SUBSTITUTION:- 
                                                                    SIMPLE STRING REPLACEMENT IS USED TO DEFINE CONSTANT . ALL MACRO IDENTIFIERS ARE IN CAPITAL LETTERS .

for example:- #define PI 3.14
                      #define count 100

b.) MACRO WITH ARGUMENT:-
                                           #define CUBE(x) (x*x*x)

c.) NESTING MACRO:-
                  #define M 5 

                  # define N M+1

2. FILE INCLUSION:-

                                     #include<stdio.h>

                                     #include"stdio.h"

WHEN THE FILE NAME IS INCLUDED WITHIN THE DOUBLE QUOTATION("") , THE SEARCH FOR THE FILE IS MADE FIRST IN THE CURRENT DIRECTORY AND THEN IN THE STANDARD DIRECTORIES .

3. CONDITIONAL COMPILATION:- 

                                                               C PREPROCESSOR PROVIDED THE FACILITIES OF CONDITIONAL COMPILATION . CONDITIONAL COMPILATION ALLOWS YOU TO CONTROL THE   COMPILATION PROCESS BY INCLUDING #if  COMMAND  IN THE PROGRAM .

for example:-    #if expression 

                             code to be included , if expression is true ,

                         # else

                            code to be included , if expression is false .

                         #end if .         

"WE SHALL DISCUSS THE OTHER PARTS OF C PROGRAM IN DETAIL IN OUR NEXT POST" .

NOTE:- IF YOU HAVE ANY CONFUSION RELATED TO THIS TOPIC , YOU CAN ASK ME ON COMMENT SECTION.😊

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