Digging around in some old archived data, I came across the source code for the PC (DOS) version of Star Wars, which consists of about 750K of ASM files - quite a lot more than I’d have guessed at. A couple of the other files indicate that this is a copy of the source we brought back from California after working on the final testing over there, so it’s definitely the ‘latest’ version. There’s also a compiled EXE, but unsurprisingly it crashes when I try and run it under Windows XP.
The source makes for a very entertaining read, at least for me, bringing back a lot of memories. It’s definitely not what you’d call a fine example of software engineering, even for its time, but it did work very well. Following is a choice excerpt, featuring few comments, and a smattering of self-modifying code which appears to be more for the sake of it than for performance in this case.
DoTrenchWalls PROC NEAR mov cx,TrenchWidth ;Draw outer walls of trench. add cx,TrenchX mov Pxl,cx add cx,CentreX mov dx,TrenchBottom mov Pyl,dx add dx,CentreY mov Sx,cx mov Sy,dx mov W cs:InnSy+4,dx mov W cs:UseLaterX+4,cx sub cx,CentreX sub dx,CentreY mov ax,ZDist mov Pzl,ax call View3d ; Same point in Distance mov Fx,cx mov Fy,dx mov bx,RecursePosition mov ResX[bx],cx mov ResY[bx],dx push cx call Msdraw mov ax,01200h add ax,TrenchY mov Pyl,ax call YView3d pop cx mov Fx,cx mov Fy,dx mov W cs:WasJustBufY+4,dx call MsDraw ; VertDraw.............!!! mov dx,Pyl add dx,CentreY mov Fy,dx push dx UseLaterX: mov Fx,0FFFFh ;self mod call MsDraw mov ax,0-TrenchWidth add ax,TrenchX mov Pxl,ax add ax,CentreX mov Sx,ax mov W cs:WasBufX10+4,ax mov dx,W [cs:InnSy+4] mov Sy,dx mov bx,RecursePosition mov dx,W ResY[bx] mov Fy,dx mov ax,ZDist mov Pzl,ax call XView3d mov Fx,cx mov W cs:UseLater2+4,cx push cx call Msdraw pop cx mov Fx,cx WasJustBufY: mov Fy,0FFFFh ;self mod call MsDraw ;VertDraw............!!! WasBufX10: mov Fx,0FFFFh ;self mod pop dx mov Fy,dx call MsDraw mov bx,RecursePosition mov cx,W ResX[bx] mov Sx,cx mov dx,W ResY[bx] mov Sy,dx mov Fy,dx UseLater2: mov Fx,0FFFFh ;self mod call HorzDraw ret DoTrenchWalls ENDP
The question now is what to do with this blast from the past, which judging by the state of the CD it was on (a 1998 archive of 1988 code), it was about to disappear forever since much of the rest of the contents wouldn’t read at all. I could try and get it working as is, or port the data and logic to a more modern environment, or I could re-archive it and come back to it in another 20 years. Probably the latter is the sensible option.
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Cool label names, Luke:
UseLater:
UseLater2:
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