Beginning graphics?

    

typedef unsigned char byte;
typedef unsigned int word;
typedef unsigned long dword;

typedef enum
{
  none = 0x00,
  text80x25 = 0x03, //or maybe 80x24 (dont remember)
  vga320x200 = 0x13
}VGAMODE;


byte far *VideoMem = (byte far*)A0000000L;
byte far *DblBuffer = NULL;


void ChangeMode (VGAMODE NewMode)
{
  __volatile__ __asm__ 
  {
    push ax
    mov ax, NewMode
    int 0x10
    pop ax
 }
}


void SetPixel (int x, int y, byte color)
{
  // Find the offset, by multiplying 'Y' by Width
  // Same as : (y * 320) + x
  VideoMem [ (y >> 6) + (y >> 8) + x ] = color;
}


void InitDblBuffer (void)
{
  DblBuffer = new byte [320 * 200];
}


void DestroyDblBuffer (void)
{
  if (DblBuffer) delete DblBuffer;
}


void SwapBuffer (void)
{
  if (DblBuffer) return;

  // We will swap 4 pixel / iteration

  dword *PtrDest = (dword *)VideoMem;
  dword *PtrSrc = (dword *)DblBuffer;

  for (dword i = 0; i < ((320 * 200) / 4); i++, PtrMem++, PtrSrc++)
    PtrDest<i> = PtrSrc[i];
}


void ClearBuffer (byte far* Mem)
{
  // We will clear 4 pixel / iteration

  dword *PtrMem = (dword *)Mem;

  for (dword i = 0; i < ((320 * 200) / 4); i++, PtrMem++)
    PtrMem[i] = 0;
}

    

    
#include <conio.h>

// define the video modes constants

#define VGA_MODE  0x0013
#define TEXT_MODE 0x0003

// define a BYTE type

typedef unsigned char byte;

// declare a pointer that points to the video memory which is

// at A000:0000 (this declaration is specifically for TC++
byte far* vga = (byte far *)0xA0000000L;

// This functions sets the mode while you''re in DOS

// you just pass the video mode constant to this function and

// it sets it for you...

// btw, INT in the ASM code stands for interrupt (like a function
// call in C... and the function parameter is move to AX which

// is one of the PC''s registers used for calculation and also

// used with interrupts just like we do in the sample code

void SetMode(unsigned short mode)
{
  asm {
    mov ax, [mode]
    int 10h
    }
}

// The following functions places a pixel on the screen

// As you already know mode13h has a resolution of 320x200

// which is 320-width and 200-height... Since the VGA screen is

// a single dimension (opposed to 2D, which would use
// a 2D array), it uses an array to access all of it''s elements
// If you know how a pointer works in C/C++ you''d know what''s

// going on in the code below. In order to place a pixel at the

// correct location, you have to multiply the Y value by
// the width (320), and then add the X value. Think about it.
// Since it''s a 1D array, and there are 320 pixels in each row,
// you have to multiply the Y value you wanna get to by 320

// and then add the additional X value.. pretty easy.. It''s gonna

// take some time to get used to it

void PutPixel(int x, int y, byte color)
{
  vga[y*320+x] = color;
}

int main()
{
  // Go into Mode 13h, which is the VGA
  SetMode(VGA_MODE);
  // Use out function to put a pixel at location X=160, Y=100,
  // with Color=15 (WHITE) which is already defined for. Well,
  // it''s defined until you change it, which you''ll learn about
  // later on.

  PutPixel(160, 100, 15);
  // Wait for a keypress

  getch();
  // Go back to text mode

  SetMode(TEXT_MODE);
  // Exit the program

  return 0;
}
    

    
#include <conio.h>

#define VGA_MODE  0x0013
#define TEXT_MODE 0x0003

typedef unsigned char byte;

byte* vga = (byte *)0xA000;

void SetMode(unsigned short mode)
{
  REGS regs;

  regs.ax = mode;
  int86(0x10, ®s, ®s);
}
void PutPixel(int x, int y, byte color)
{
  vga[y*320+x] = color;
}

int main()
{
  SetMode(VGA_MODE);
  __djgpp_enable_nearptr();
  vga += __djgpp_conventional_base;
  PutPixel(160, 100, 15);
  getch();
  SetMode(TEXT_MODE);
  __djgpp_disable_nearptr();
  return 0;
}