Questions tagged [dos-exe]

16 bits DOS MZ executable file format

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How to maintain function ordering in an executable when replacing machine code with C step by step?

I am working on reversing a DOS game consisting of 16-bit MZ EXE files. I was able to determine the exectuables were generated by Microsoft C v 5.10, and loading the signatures from the static ...
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0answers
173 views

Where to start analyzing a 16 bit dos program?

I've tried to analyze this small exe online. I've tried with https://onlinedisassembler.com/odaweb/ (link) but it's hard for me to get the first question: Why the tool doesn't try to detect the set ...
0
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1answer
120 views

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\...
9
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2answers
527 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
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0answers
241 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 ...
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1answer
454 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
673 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
89 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? ...
3
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2answers
5k 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 ...
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2answers
195 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
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2answers
718 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 (...
2
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2answers
5k 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
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1answer
146 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
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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 ...
2
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2answers
26k 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
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4answers
1k 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 ...
27
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8answers
42k 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
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3answers
8k 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++ ...