from Hacker News

A Guide to Debug.exe

by infinity on 3/30/15, 6:35 PM with 10 comments

• by TheCraiggers on 3/30/15, 9:03 PM

  Reminds me about how I nearly got kicked out of highschool for changing the background color of sol.exe.

  Back in my HS days, the "computer class" teacher (in quotes because it wasn't a computer class at all, rather a typing class) used to walk around and say "I don't want to see any green screens". Green, of course, being the background color of the built-in solitaire card game back in Windows 3.11 days.

  I took a screenshot as a bmp, and found the hex value for the background color. Then I fired up debug, having nearly no idea what I was doing, searched for that hex value, found it, and then changed it to a nice mauve color. Thought it would be funny, maybe even praise-worthy.

  Instead, the teacher lost his shit. These computers were "locked down" by basically just putting all the admin-type shortcuts into a password protected program group. But File->Run was still there, and it had no problem firing up COMMAND.COM. I didn't think it would be a big deal, but of course it was completely blown out of proportion by the teacher, who didn't exactly like my attitude.

  I still dislike that man.

• by nbaksalyar on 3/30/15, 8:52 PM

  It's interesting that you can write relatively complete programs with Debug.exe assembler.

  This link made me remember my weird experiment from 2009 to write a NES Battle City [1] clone with debug.exe assembler [2]. Of course it wasn't completed, but nevertheless, it even switches to a graphic mode and draws a single sprite on the screen and takes input from the keyboard. :)

  The demo [3] still should be working in DosBox.

  [1] https://en.wikipedia.org/wiki/Battle_City_(video_game)

  [2] https://code.google.com/p/asmbattlecity/source/browse/

  [3] https://code.google.com/p/asmbattlecity/downloads/detail?nam...

• by chris_overseas on 3/30/15, 10:42 PM

  This article really brought back some great memories for me. I learned about computers as a kid back in the early 80s on an MS-DOS clone PC. The only manuals I had was one listing the various MS-DOS commands (sadly, excluding anything about debug.exe though) and one that was a command reference for gwbasic.exe [1].

  I spent many hours trying to write games in gw-basic but quickly realised that the performance was atrocious, to say the least. Eventually I stumbled across a magazine that had a two-page article about debug.exe and it was my gateway to a whole new hidden world. I went on to learn 8086 assembly with debug.exe by trial and error and from stepping through other programs. Eventually I figured out I could write little 8086 assembly routines in debug.exe myself, take the sequence of bytes that made up that routine, declare them as a DATA statement in a BASIC program and then just make call that DATA line to run the machine code directly [2]. It wasn't until many months later I finally managed to get my hands on some compilers and assemblers (Borland Turbo Pascal and Turbo Assembler being my favourites back then) which of course made my life a whole lot easier! I continued to use debug.exe for many years though, primarily for reverse engineering.

  I've just managed to dig up an obfuscated "Hello World" batch file I wrote many years ago that makes use of debug.exe, see [3] below (If you actually want to run it you'll probably need an MS-DOS emulator [4][5] or an older version of Windows that still has debug.exe).

  [1] http://en.wikipedia.org/wiki/GW-BASIC

  [2] http://www.antonis.de/qbebooks/gwbasman/appendix%20d.html

  [3] http://www.redyeti.net/extra/hello.bat

  [4] https://jamesfriend.com.au/pce-js/ibmpc-games/

  [5] http://www.dosbox.com/

• by whoopdedo on 3/31/15, 12:22 AM

  One of the more useful things that was done with debug.exe was a binary-to-ascii converter for sending files in email or usenet and the recipient didn't need any extra tools. I think the program was called "xxdebug" after xxencode which was a descendent of uudecode. But Google doesn't help, so either my memory is wrong or the internet has forgotten.

  I'm positive I have it on an archived disk somewhere. If I were inclined to resurrect it.

• by Zardoz84 on 3/30/15, 10:37 PM

  Another relic of old times is the font installer embed on Windows. Since Windows 3.1 to Windows XP has the exact same program! You can check that it's keeps using the old GUI to navigate across the filsesystem, not showing the "Destop" false root.

  On Windows Vista and forward was replaced by something more modern.

• by chrisbennet on 3/31/15, 11:26 AM

  The smallest program I ever wrote, I wrote using debug.exe. It was 7 bytes long. I think it reset the graphics card. This was around 1991.