The standard .com sceleton on fasm?

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FASMresearcher

Joined: 28 May 2008
Posts: 24

FASMresearcher 15 Jun 2008, 14:48

Hi, All!
Question is simple.

Must I use the some standard sceleton during writing the FASM .com executable code?
For example:

Code:

.model tiny
.386
org 100h
.code
......
entry_point:


end entry_point

If not, the commands like:

Code:

push cs
pop  ds
and others...

Is it necessarily?
And how I can mark the start/end of programm?

15 Jun 2008, 14:48

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 19872
Location: In your JS exploiting you and your system

revolution 15 Jun 2008, 14:54

See the example that comes with the fasm download.

15 Jun 2008, 14:54

rCX

Joined: 29 Jul 2007
Posts: 172
Location: Maryland, USA

rCX 15 Jun 2008, 15:28

Quote:

Must I use the some standard sceleton during writing the FASM .com executable code?

All you really need is...

Code:

org 100h
;code goes here

...but you can also use...

Code:

format binary as "com"  
use16                          ;use 16 bit registers
org 100h
;code goes here

As revolution said you should look at the COMDEMO, or LIFE examples that come with fasm. Wink

_________________
"To define Recursion we first need to define Recursion."

15 Jun 2008, 15:28

FASMresearcher

Joined: 28 May 2008
Posts: 24

FASMresearcher 16 Jun 2008, 08:50

revolution wrote:

See the example that comes with the fasm download.

Great thanks!

16 Jun 2008, 08:50

FASMresearcher

Joined: 28 May 2008
Posts: 24

FASMresearcher 16 Jun 2008, 08:53

rCX wrote:

...but you can also use...

Code:

format binary as "com"  
use16                          ;use 16 bit registers
org 100h
;code goes here

Great thanks!

As revolution said you should look at the COMDEMO, or LIFE examples that come with fasm. Wink

_________________
"To define Recursion we first need to define Recursion."[/quote]

16 Jun 2008, 08:53

DOS386

Joined: 08 Dec 2006
Posts: 1898

DOS386 16 Jun 2008, 09:54

> .model tiny

Not needed and prohibited Laughing

> .386

Regrettably not supported ... but there are some macros

> org 100h

Required ... or org $0100 Wink

Code:

.code
entry_point:
end entry_point

Not needed and prohibited Laughing

Code:

push cs
pop  ds

Required for MZ, optional for COM Wink

> And how I can mark the start/end of programm?

Not needed Wink

Code:

; END.

Code:

format binary as "COM" ; better than undocumented guesses   
use16                  ; use 16 bit code (default anyway)
org $0100              ; critical       
;code goes here

Code:

assume blah:yes

Not needed and prohibited Laughing

_________________
Bug Nr.: 12345

Title: Hello World program compiles to 100 KB !!!

Status: Closed: NOT a Bug

16 Jun 2008, 09:54

wht36

Joined: 18 Sep 2005
Posts: 106

wht36 22 Jun 2009, 14:39

org 100h - because DOS loads .com files at address 100h

bytes 0-FF = program segment prefix = holds command line, environment table pointer, file control blocks, etc. (check HelpPC)

22 Jun 2009, 14:39

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