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16 bits DOS MZ executable file format

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Within A Folder of 100s of 16-bit MS-DOS Disassembled EXEs Identify Ones That Need/Use DOS/4GW

So far I batch disassembled all files using following PowerShell and IDA: $files = Get-Content S:\files.txt ForEach ($file in $files) { Write-Host "Processing $file" &"C:\Program Files\...
8
votes
2answers
319 views

How did this 80286 detection code work?

I'm poking through a disassembled 16-bit DOS game circa 1992. The original system requirements state that the game needs an IBM AT-compatible machine or later, with the 286 processor, to run. And ...
1
vote
0answers
139 views

IDA fixups, why and how

I'm using IDA 7 Freeware, not Pro. I've been using IDC to re-invent the wheel somewhat, but I'm learning a ton of stuff as I go along. I have a 16-bit MSDOS exe which I'm reversing. I stripped out ...
1
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1answer
341 views

PE DOS stub content not commands

Does anyone know why the PE DOS stub often includes repetitive looking data that does not seem to be valid 16bit commands?
3
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1answer
529 views

debugging a graphical msdos game

There is a DOS game I want to run through a debugger. I tried using (FreeDos) DEBUG.COM over DosBox. But the problem is that this game uses graphics, and this messes up the output of DEBUG.COM. Is ...
2
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0answers
77 views

COBOLII-MB 2.xx

I have a really old cobol program that was used to store some data, the company is no loger active and the program had to receive a key every 3 months. What tools I can use to reverse a cobol program? ...
2
votes
2answers
3k views

Disassembling an MS-DOS EXE

I've been disassembling an MS-DOS EXE and I've been using this link http://www.delorie.com/djgpp/doc/exe/ to make heads and tails of the binary. The header seems to be an older version compared to ...
0
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2answers
177 views

Issues rewriting portions of DOS app's assembly

I am working on editing an old DOS program's assembly, but I'm running into some odd issues. I'm using IDA Pro 6.4 and a hex editor to patch. I'm code-caving the new data by removing old stuff never ...
2
votes
2answers
552 views

How to extract debug information from a DOS executable compiled with Watcom C/C++?

I have a DOS executable which has been compiled with Watcom C/C++ 10.0. That EXE has debug symbols inside. I was wondering if there is any tool that allow to dump or extract that debug information (...
1
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2answers
3k views

How to quickly distinguish PE/DLL/DOS-MZ files based on magic numbers?

I know that the specifications of the Microsoft PE/DLL/DOS-MZ files states that the two first bytes of a PE/DLL/DOS-MZ file is MZ (0x4d,0x5a) orZM(0x5a,0x4d`). The problem with such a small signature ...
3
votes
1answer
141 views

16 bit Dos string concat function

I just got into reversing, i'm a bit puzzled by a part of the following code. I know what its doing, from a technical aspect, but i don't really understand why its doing it. This is the part I have a ...
3
votes
3answers
2k views

How to edit an .exe file without overwriting previous information

A qualifier - all I know of what I'm about to explain has been gathered from spending the last few hours researching to solve my problem, so forgive the naivety and clumsiness of a non-expert in this ...
1
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2answers
21k views

Is it possible to extract or otherwise edit the source code of an .exe file?

I have a small executable that I downloaded from the net, and that runs in the Command Line, which makes me think it may be a DOS program. The program works perfectly, but due to being developed by a ...
5
votes
4answers
879 views

Any correlation between DOS Program Segment Prefix and the base address of loaded executable?

I'm using IDA to disassemble Test Drive III. It's a 1990 DOS game. The *.EXE has MZ format. The game uses a number of anti-reversing features such as copying its code to segment (PSPseg+2be7) where ...
24
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8answers
33k views

Decompiling a 1990 DOS application

I have some crucial data written decades ago by an ancient 16bit DOS application. There are no docs, no source, and no information about the author. Just the 16 bit exe. I guess it's time for me to ...
11
votes
3answers
7k views

Reverse engineer an old DOS QBasic executable

I recently decided to try my hand at reverse engineer an old DOS text based game that was coded in QBasic. I found some info online about old DOS games disassembly but mostly for Wacom compiled C/C++ ...