Space Invaders

[_japheth]

Hello Friends,

I played with Paul S. Reid's "Space Invaders" source code a bit. It's a clone of the famous Arcade game of the 1980s, written with TASM, using VGA mode 0x13 ( 320x200x8 ). The first step was to convert it to Masm syntax. Then, just for fun, I made protected-mode variants, for DPMI 16-/32-bit and Win32.

The Win32 variant uses the (now "legacy") DirectDraw API, and runs in 640x480x8 mode; this seems to be supported by all Windows versions. It might run too fast on new machines - that probably can be fixed rather easily by switching to DirectDraw7 and then select a vertical refresh rate of 60 or 70.

The DOS versions run fine in true DOS and in DosBox. However, with Qemu and VBox there's a problem - they don't support "vertical retrace" synchronisation ( an interesting discussion about this is here: https://forum.osdev.org/viewtopic.php?t=31917 ) - so the game runs way too fast there.

Btw, the game is copyright Paul S. Reid, but distribution of binary and source is ok....

[Vortex]

Hi Japheth,

Nice work

For those who would like to try the game, here is how to use the keyboard : left and right arrow keys to move the cannon and SPACE to fire.

[FORTRANS]

Hi,

   The Windows version works well with my Win2k system.

Regards,

Steve

[daydreamer]

nice work japhet 
its design is old dos game run ASAP=run As fast as possible,it makes my cpu go full speed with turbo and cooler fan goes full speed(windows version)

but I already have a different energy setting for lower cpu speed to switch to when run old win95 games for that to solve that kinda problem
 

[FORTRANS]

Hi,

   I tried INVADERS.COM, INVADERS.EXE, and INVADE32.EXE in a
Windows NTVDM, and all ran normally.  INVADERS.COM and
INVADERS.EXE had an odd long pause after dying until I could
quit.

   Trying in an OS/2 VDM, all ran too fast.  Same odd Pauses.

Regards,

Steve N.

[_japheth]

its design is old dos game run ASAP=run As fast as possible,it makes my cpu go full speed with turbo and cooler fan goes full speed(windows version)

Yes, the program uses PeekMessage() in the message loop, thus returning instantly if no message is available. IIRC inserting a Sleep(1) call in the message loop - probably just before the WaitForVerticalBlank() call - should reduce cpu load significantly.

[_japheth]

A little update

• - sound added to the Win32 version - just using the simple Beep(), no need for SFX.
• - duration of sound in DOS versions no longer depends on cpu speed.