PC Underground/UNDERGROUND.ISO/graphic/starx.pas

Pascal/Delphi Source File | 1995-07-28 | 2KB | 55 lines

{$G+}
Uses ModeXLib,Crt;
Var Stars:Array[0..500] of Record
                              x,y,Plane:Integer;
                            End;
  st_no:Word;
  vscreen:Pointer;
  vpage:Word;
  palette:Array[0..768] of Byte;

Procedure PutPixel(x,y,col:word);assembler;
{sets pixel (x/y) to color col (Mode X)}
asm
  mov ax,0a000h                 {load segment}
  mov es,ax

  mov cx,x                      {define Write Plane}
  and cx,3                      {as x mov 4}
  mov ax,1
  shl ax,cl                     {set appropriate bit}
  mov ah,al
  mov dx,03c4h                  {Timing Sequencer}
  mov al,2                      {Register 2 - Write Plane Mask}
  out dx,ax

  mov ax,80                     {Offset = Y*80 + X div 4}
  mul y
  mov di,ax
  mov ax,x
  shr ax,2
  add di,ax                     {load offset}
  mov al,byte ptr col           {load color}
  mov es:[di],al                {and set pixel}
End;

Begin
  Randomize;                    {initialize random numbers}
  Init_ModeX;
  Repeat                        {executed once per display}
    For St_no:=0 to 500 do Begin{calculate new position for each start}
      With Stars[st_no] do Begin
        PutPixel(x,y,0);        {clear old pixel}
        Dec(x,Plane shr 5 + 1); {continue moving}
        if x <= 0 Then Begin    {left ?}
          x:=319;               {then reinitialize}
          y:=Random(200);
          Plane:=Random(256);
        End;
        PutPixel(x,y,Plane shr 4 + 16);  {set new pixel}
      End;
    End;
  Until KeyPressed;             {run until key pressed}
  TextMode(3);
End.