#include <dos.h>
#include <sys/nearptr.h>

typedef struct rgb_color_type
  {
  unsigned char red;
  unsigned char green;
  unsigned char blue;
  } rgb_color;

char *video_buffer = (char *)0xa0000,*double_buffer;

void set_video_mode(int mode)
{
union REGS regs;
regs.x.ax = mode;
int86(0x10, &regs, &regs);
}

void set_palette_register(unsigned char index, rgb_color *color)
{
outportb(0x3c6,0xff);
outportb( 0x3c8,index);
outportb(0x3c9,color->red);
outportb(0x3c9,color->green);
outportb(0x3c9,color->blue);
}

void put_pixel(short int x, short int y, char color)
{
double_buffer[(y << 8) + (y << 6) + x] = color;
}

void main()
{
rgb_color col={63,0,0};//red
__djgpp_nearptr_enable();
video_buffer += __djgpp_conventional_base;
double_buffer=(char *)malloc(64000);
set_video_mode(0x013);
set_palette_register(1,&col);
memset((char *)double_buffer,0,64000);//Set all pixels to index zero i.e. clear the screen
put_pixel(160,100,1);
memcpy((char *)video_buffer,(char *)double_buffer,64000);
delay(3000);
set_video_mode(0x03);
__djgpp_nearptr_disable();
free(double_buffer); // dont omit this or memory errors will occur
}

//Complile this program with this command: GCC EX3.C -O EX3.EXE -LM