What is a pre-processor?

fig: pre-processor

Pre-processor is a program that processes its input data to produce output that is used as input to another program, which will pre-process our source code, for that we will use preprocessor directives to pre-processor. Pre-processor are started with the # symbol. We don’t need to use a semicolon in the pre-processor. 

Syntax  

 

#include < stdio.h > 

 

They are used before the complication of a program, so they are written at the top of the program.  

#include this will specify the name of the file to enter. 

#define this will define a macro  

#undefine this will undefine the macro  

#if 

#else  

#end if etc. are the example of pre-processor.  

 

Pre-processor can be category in 3 parts they are:- 

1) macro substitution  

 

2) file inclusion  

 

3) compiler control  

 

First program 

#include < stdio.h > , #include < conio.h> They are a library file to run a program.<stdio.h> includes input-output and printf function. where <conio.h> include Clrscr () ( is used to clear the screen ) and getch () (is used to hold the answer for a while on the screen.) in this program, we are not defining any variable so we have only the executable part which we have shown below.

 

#include <stdio.h> 

#include <conio.h> 

// this is executable part 

int main() 

{ 

    clrscr(); 

    printf("here is your name..."); // write anything u want to see... 

    getch(); 

    return 0; 

}