All Questions
Tagged with executables ms-dos
8 questions
3
votes
2
answers
517
views
Why does my MZ executable's BSS inflate by ~1,5KB after linking fopen() with MSC?
For a game reversing project, I am trying to undo linking with the C library performed by the MSC 5.1 C compiler+linker.
To that end, I have created a simple executable that does nothing except ...
- 973
13
votes
1
answer
2k
views
What was the purpose of the ‘overlay number’ field in the MZ executable format?
Many materials covering the layout of MZ executables (RBIL, for example, and even a comment in MS-DOS 2.0 source code) describe the word at offset +0x1a as the ‘overlay number’, with the value zero ...
- 24.9k
11
votes
1
answer
618
views
How can I properly execute and clean up after a DOS MZ executable loaded into memory with int21 function 4b01h?
Ralf Brown's Interrupt List describes a subvariant of the DOS int21/4Bh function with AL=01, where the program is loaded into memory and a PSP + stack are allocated for it, but the program is not ...
- 973
13
votes
6
answers
6k
views
How can I tell whether a DOS-looking exe. requires a 32-bit CPU to run?
Is there some simple method for determining if a DOS (or OS/2, or Windows etc.) binary (.exe or .dll) is 16-bit or 32-bit? The Linux file command just says "executable".
I want to ...
- 2,122
2
votes
2
answers
1k
views
Why does changing a DOS/Windows EXE cause it to not run? [closed]
If I hex-edit an EXE for DOS or Windows, by adding or removing some text for example, it will no longer run.
If I just change a single char around to a different one, it may run.
Is this some anti-...
23
votes
1
answer
4k
views
How did large .COM files work?
An MS-DOS .com file is just raw code/data without header, thus no linking information, and was limited to be loaded into just one segment (64kB). That's the reason corrupted binaries would print "...
- 1,719
13
votes
2
answers
2k
views
Are .COM executable binaries real mode or protected mode?
Windows and DOS binary executable files with the .EXE extension have an MZ header in them and nowadays also a PE header.
But before these there used to also be .COM binary executable files and they ...
- 7,874
18
votes
5
answers
5k
views
What tools were used in late MS-DOS era for reverse engineering and patching binary executables?
In the late MS-DOS era, what were the state of the art software tools for reverse engineering and patching binaries, i.e. .exe and .com files?
A simple list of the tools that were "state of the art", ...
- 1,533