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

int main(void) 
{ 
   /* select a driver and mode that supports the use */ 
   /* of the setrgbpalette function.                 */ 
   int gdriver = VGA, gmode = VGAHI, errorcode; 
   struct palettetype pal; 
   int i, ht, y, xmax; 

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

   /* read result of initialization */ 
   errorcode = graphresult(); 
   if (errorcode != grOk)  /* an error occurred */ 
   { 
      printf("Graphics error: %s\n", grapherrormsg(errorcode)); 
      printf("Press any key to halt:"); 
      getch(); 
      exit(1); /* terminate with an error code */ 
   } 

   /* grab a copy of the palette */ 
   getpalette(&pal); 

   /* create gray scale */ 
   for (i=0; i<pal.size; i++) 
      setrgbpalette(pal.colors[i], i*4, i*4, i*4); 

   /* display the gray scale */ 
   ht = getmaxy() / 16; 
   xmax = getmaxx(); 
   y = 0; 
   for (i=0; i<pal.size; i++) 
   { 
      setfillstyle(SOLID_FILL, i); 
      bar(0, y, xmax, y+ht); 
      y += ht; 
   } 

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