#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/mman.h>
#include <stdio.h>
#include <string.h>

/* change to 0xb000 for monochrome displays */
#define TEXT_OFFSET		0xb8000
#define TEXT_LENGTH		(80 * 25 * 2)	// = 4000

#define ATTR_OFF        0	/* All attributes off */
#define ATTR_BOLD       1	/* Bold On */
#define ATTR_DIM        2	/* Dim (Is this really in the ANSI standard? */
#define ATTR_UNDERLINE  4	/* Underline (Monochrome Display Only */
#define ATTR_BLINK      5	/* Blink On */
#define ATTR_REVERSE    7	/* Reverse Video On */
#define ATTR_INVISIBLE  8	/* Concealed On */

#define COLOR_BLACK     0	/* Black */
#define COLOR_RED       1	/* Red */
#define COLOR_GREEN     2	/* Green */
#define COLOR_YELLOW    3	/* Yellow */
#define COLOR_BLUE      4	/* Blue */
#define COLOR_MAGENTA   5	/* Magenta */
#define COLOR_CYAN      6	/* Cyan */
#define COLOR_WHITE     7	/* White */

static const char *device = "/dev/mem";

int main ()
{
   int i,fd;
   unsigned char *text,*s,*d;
   char buf[TEXT_LENGTH],tmp[TEXT_LENGTH];

   /*
	* Map the text memory to something we can access
	*/

   if ((fd = open (device,O_RDWR | O_SYNC)) < 0)
	 {
		perror ("open()");
		exit (1);
	 }
   text = mmap (NULL,TEXT_LENGTH,PROT_READ | PROT_WRITE,MAP_SHARED,fd,TEXT_OFFSET);
   if (text == MAP_FAILED)
	 {
		perror ("mmap()");
		exit (1);
	 }

   /*
	* Do the tricks
	*/

   /* copy entire screen to temp buf */
   memcpy (buf,text,TEXT_LENGTH);

   /* flip buf upside-down */
//   memcpy (tmp,buf,TEXT_LENGTH);
//   for (i = 0, s = buf, d = tmp + TEXT_LENGTH - 80*2; i < 25/2; i++, s += 80*2, d -= 80*2)
//	 memcpy (d,s,80*2);
//   memcpy (buf,tmp,TEXT_LENGTH);

   /* set color to bright cyan */
   for (i = 1; i < TEXT_LENGTH; i += 2) buf[i] = /*COLOR_CYAN*/5;

   /* copy buf to screen */
   memcpy (text,buf,TEXT_LENGTH);
   msync (text,TEXT_LENGTH,MS_SYNC);

   /*
	* Clean up and exit
	*/

   munmap (text,TEXT_LENGTH);
   close (fd);
   exit (0);
}