To execute a function before the main() get executed

CODE:
#include<stdio.h>
#include<conio.h>


void wish()
{
 printf("\nHello ");
}


#pragma startup wish 
/*this preprocessor statement make wish() 
get first executed before main()*/


void main()
{
 printf("Coder!");
 getch();
}


OUTPUT:
Hello Coder!

Program to print line number and filename

CODE:

#include<stdio.h>
#include<conio.h>


void main()
{
 clrscr();
 printf("Line %d of %s",__LINE__,__FILE__);
 getch();
}


OUTPUT:
Line 7 of ..\..\CPROGRAM.C

To create a variable that takes only 3 bits memory

CODE:
#include<stdio.h>
#include<conio.h>
struct abc

{

   unsigned xyz : 3; //takes 3 bit memory

}st;

void main()

{
   clrscr();
   st.xyz = 7; //(1112) 
   printf("\nValue of xyz(before increment) : %d",st.xyz);
   st.xyz++;
   printf("\nValue of xyz(after increment) : %d",st.xyz);
   getch();
}


OUTPUT:
Value of xyz(before increment) : 7
Value of xyz(after increment) : 0