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

/* function prototypes */ 
int huge detectEGA(void); 
void checkerrors(void); 

int main(void) 
{ 
   int gdriver, gmode; 

   /* install a user written device driver */ 
   gdriver = installuserdriver("EGA", detectEGA); 

   /* must force use of detection routine */ 
   gdriver = DETECT; 

   /* check for any installation errors */ 
   checkerrors(); 

   /* initialize graphics and local variables */ 
   initgraph(&gdriver, &gmode, ""); 

   /* check for any initialization errors */ 
   checkerrors(); 

   /* draw a line */ 
   line(0, 0, getmaxx(), getmaxy()); 

   /* clean up */ 
   getch(); 
   closegraph(); 
   return 0; 
} 

/* detects EGA or VGA cards */ 
int huge detectEGA(void) 
{ 
   int driver, mode, sugmode = 0; 

   detectgraph(&driver, &mode); 
   if ((driver == EGA) || (driver == VGA)) 
      /* return suggested video mode number */ 
      return sugmode; 
   else 
      /* return an error code */ 
      return grError; 
} 

/* check for and report any graphics errors */ 
void checkerrors(void) 
{ 
   int errorcode; 

   /* read result of last graphics operation */ 
   errorcode = graphresult(); 
   if (errorcode != grOk) 
   { 
      printf("Graphics error: %s\n", grapherrormsg(errorcode)); 
      printf("Press any key to halt:"); 
      getch(); 
      exit(1); 
   } 
}