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Index > DOS > Are there advantages of using exe insted of com executables?

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rCX



Joined: 29 Jul 2007
Posts: 166
Location: Maryland, USA
rCX
Are there advantages of using exe insted of com executables?
Post 24 May 2009, 20:10
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revolution
When all else fails, read the source


Joined: 24 Aug 2004
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revolution
rCX wrote:
Are there advantages of using exe insted of com executables?
Yes.

A few to get you started: code+data>64kB, arbitrary entry point, pre-allocated segments, ...
Post 25 May 2009, 05:59
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sinsi



Joined: 10 Aug 2007
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sinsi
And no.
Post 25 May 2009, 06:05
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Tomasz Grysztar



Joined: 16 Jun 2003
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Tomasz Grysztar
The non-MZ .com executable file cannot be larger than 64K, so if you need to have more code there, you are forced to use the MZ format. Though you can still disguise MZ with a .com extension - it's not the file extension that determines the type of executable.

Also, MZ has a nice feature of relocations, which non-MZ lacks.
Post 25 May 2009, 12:27
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revolution
When all else fails, read the source


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revolution
Plus the things I mentioned in my posting above. But you have to reveal the hidden to see what I wrote.
Post 25 May 2009, 12:46
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rCX



Joined: 29 Jul 2007
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rCX
revolution wrote:
A few to get you started: code+data>64kB, arbitrary entry point, pre-allocated segments, ...

Tomasz Grysztar wrote:
The non-MZ .com executable file cannot be larger than 64K, so if you need to have more code there, you are forced to use the MZ format.


So for programs smaller than 64Kb com files are okay...
Post 25 May 2009, 15:19
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Tomasz Grysztar



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Tomasz Grysztar
revolution wrote:
pre-allocated segments

Well, the .com program has the memory segments following the program segment pre-allocated aswell.
Post 25 May 2009, 15:31
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revolution
When all else fails, read the source


Joined: 24 Aug 2004
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revolution
pre-allocated segment[ register]s? I don't remember if DOS does this or not.


Last edited by revolution on 25 May 2009, 15:47; edited 1 time in total
Post 25 May 2009, 15:45
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revolution
When all else fails, read the source


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revolution
rCX wrote:
So for programs smaller than 64Kb com files are okay...
Sure, for DOS no problem.
Post 25 May 2009, 15:47
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Borsuc



Joined: 29 Dec 2005
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Borsuc
Can't you just load an external .bin file with more code? Wink
Post 25 May 2009, 23:27
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revolution
When all else fails, read the source


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revolution
Yes, it is known as runtime linking. Often they come as DLL files. But that is no longer a single .exe or .com file anymore.
Post 26 May 2009, 02:02
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neville



Joined: 13 Jul 2008
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neville
I use FASM to create "memory image" executables up to about 512K in size (DOS memory limit). These are (or could be) DOS .COM programs with CS=DS=ES=SS, IP=0100h, SP=0FFFEh etc.

They CAN be run in DOS but not directly from the command prompt (only because DOS checks for >64K size).

Instead, they can be loaded into DEBUG or other compatible debugger and executed with the "g" command.

_________________
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Post 27 May 2009, 05:30
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DOS386



Joined: 08 Dec 2006
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DOS386
rCX wrote:
Are there advantages of using exe insted of com executables?


YES.

* For MZ EXE you can control stack location and size, for COM it's just SS=CS and SP=$FFFE

* For MZ EXE you can control memory hogging, COM always hogs the complete biggest fragment

* MZ has a Sigi and header, safer to recognize (but DOS is stupid and loads broken MZ's and even EXE's having no MZ at all - as COM)

* You can include Win32 stuff into a MZ EXE, OTOH not into a COM

* MZ can be > 64 KiB (but has fixups then Sad )

revolution wrote:










Nothing as usual ... or is it hidden again Shocked ?

See: http://board.flatassembler.net/topic.php?t=9834
Post 30 May 2009, 12:17
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