1nnOc3nt

#include <stdio.h>
#define pi 3.14
#ifdef __unix__ /* __unix__ is usually defined by compilers targeting Unix systems */
printf("using linux");
#elif defined _WIN32 /* _WIN32 is usually defined by compilers targeting 32 or 64 bit Windows systems */
printf("using windows");
#endif

int main(int argc, char const *argv[])
{

1nnOc3nt

int main(int argc, char const *argv[])
{
  printf("Hello World!\nThis is pi number: %2f", pi); //This is a comment
  return 0;
}

------------------------------------------------------------------------------------------------
  
# 1 "hello.c"

1nnOc3nt

#define pi 3.14
printf("Hello World!\nThis is pi number: %2f", pi);

-------------------------------------------------------------------------------------------------

printf("Hello World!\nThis is pi number: %2f", 3.14);

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#define AND &&
#define OR ||
#define PI 3.14
#define EXCELLENT (a>=75)
#define ALERT printf("Security Alert!!")
#define MIN 1
#define MAX 9
#define MIDDLE (MIN+MAX)/2

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#define ISEXCELLENT(x) (x>=75)
#define ISLOWER(x) (x>=97 && x<=122)
#define HLINE for(i=0; i<40; i++)\
                  printf("_");

1nnOc3nt

#include <stdio.h>

---------------------------------------------------------------------------------------------

# 1 "hello.c"
# 1 "<built-in>"
# 1 "<command-line>"
# 31 "<command-line>"
# 1 "/usr/include/stdc-predef.h" 1 3 4
# 32 "<command-line>" 2

1nnOc3nt

struct foo 
{
    int member;
};

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#include "grandparent.h"

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#include "grandparent.h"
#include "parent.h"

1nnOc3nt

struct foo 
{
    int member;
};
struct foo 
{
    int member;
};