TheDraw COM File

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|released=1989
 
|released=1989
 
}}
 
}}
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'''TheDraw COM File''' is a format for [[ANSI Art]]-style character graphics, associated with the DOS software [[TheDraw Save File|TheDraw]]. The format was introduced in TheDraw v3.20 (1989-04).
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'''TheDraw COM File''' is a format for a character graphics screen, associated with the DOS software [[TheDraw Save File|TheDraw]]. The format was introduced in TheDraw v3.20 (1989-04).
  
 
It is in the form of a [[DOS executable (.com)|DOS .COM]] file that, when executed, prints the graphics to the screen.
 
It is in the form of a [[DOS executable (.com)|DOS .COM]] file that, when executed, prints the graphics to the screen.
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There are three "types" of the format, distinguished by the byte at offset 6 having value 0, 1, or 2.
 
There are three "types" of the format, distinguished by the byte at offset 6 having value 0, 1, or 2.
  
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Types 1 and 2 were introduced in version 4.00. TheDraw selects the type to use automatically. Type 1 seems to be rare, and is used only if the image is incompressible.
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Types 1 and 2 were introduced in version 4.00. TheDraw selects the type to use automatically. Type 1 is rare; it is used only if the image is incompressible.
  
 
== Identification ==
 
== Identification ==
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=== Identification - basic ===
 
Type 0 files start with bytes {{magic|eb 3d 90}}, and have <code>00</code> at offset 6.
 
Type 0 files start with bytes {{magic|eb 3d 90}}, and have <code>00</code> at offset 6.
  
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See also [[P-Screen COM Screen]], which looks a lot like type 0, except for the different signature string.
 
See also [[P-Screen COM Screen]], which looks a lot like type 0, except for the different signature string.
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=== Identification - advanced ===
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(For convenience, we include [[P-Screen COM Screen]] here, as it may need to be distinguished from TheDraw COM.)
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The strings near the start of the file were often edited, so are not ideal signatures. The 7 bytes at offset 2 are used for various purposes, and also may not be good for identification.
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 +
That leaves the two bytes at the beginning of the file ("BoF") -- a jump instruction -- and the viewer machine code that it jumps to. These parts of the file seem to be identical in all files of a given type. Here's a table of viewer code locations:
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{| class="wikitable"
 +
!Type !! BoF !! Viewer offs., size !! Payload offs.
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|-
 +
|0        || <code>eb 3d</code> || 63, 113 || 176
 +
|-
 +
|1        || <code>eb 18</code> || 26, 68  || 94
 +
|-
 +
|2        || <code>eb 3d</code> || 63, 177 || 240
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|-
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|P-Screen || <code>eb 3d</code> || 63, 166 || 229
 +
|}
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 +
The following table is just one suggestion for signatures that could be used. It uses bytes starting with the instruction that contains the pointer to the payload data. (This pointer is different in all known versions, and it also ought to make false positives from unrelated COM files highly unlikely.)
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 +
{| class="wikitable"
 +
!Type !! Sig. offs. !! Sig. bytes
 +
|-
 +
|0        || 117 || <code>8d 36 b0 01 fc 57 8b 0e 05 01 80 3e</code>
 +
|-
 +
|1        || 34  || <code>be 5e 01 8b 0e 04 01 fc bb 00 b0 3c</code>
 +
|-
 +
|2        || 104 || <code>be f0 01 ba da 03 b3 09 8b 0e 04 01</code>
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|-
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|P-Screen || 117 || <code>be e5 01 fc 57 8b 0e 05 01 80 3e 03</code>
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|}
  
 
== Specifications ==
 
== Specifications ==

Latest revision as of 15:16, 10 February 2026

File Format
Name TheDraw COM File
Ontology
Extension(s) .com
Released 1989

TheDraw COM File is a format for a character graphics screen, associated with the DOS software TheDraw. The format was introduced in TheDraw v3.20 (1989-04).

It is in the form of a DOS .COM file that, when executed, prints the graphics to the screen.

Contents

[edit] Format details

There are three "types" of the format, distinguished by the byte at offset 6 having value 0, 1, or 2.

Types 1 and 2 were introduced in version 4.00. TheDraw selects the type to use automatically. Type 1 is rare; it is used only if the image is incompressible.

[edit] Identification

[edit] Identification - basic

Type 0 files start with bytes eb 3d 90, and have 00 at offset 6.

Type 1 files start with bytes eb 18 90, and have 01 at offset 6.

Type 2 files start with bytes eb 3d 90, and have 02 at offset 6.

Types 0 and 2 have the signature string "TheDraw COM file Screen Save" at offset 9, followed by byte 0x1a.

Type 1 has the shorter string "TheDraw COM file" at offset 9, followed by 0x1a.

See also P-Screen COM Screen, which looks a lot like type 0, except for the different signature string.

[edit] Identification - advanced

(For convenience, we include P-Screen COM Screen here, as it may need to be distinguished from TheDraw COM.)

The strings near the start of the file were often edited, so are not ideal signatures. The 7 bytes at offset 2 are used for various purposes, and also may not be good for identification.

That leaves the two bytes at the beginning of the file ("BoF") -- a jump instruction -- and the viewer machine code that it jumps to. These parts of the file seem to be identical in all files of a given type. Here's a table of viewer code locations:

Type BoF Viewer offs., size Payload offs.
0 eb 3d 63, 113 176
1 eb 18 26, 68 94
2 eb 3d 63, 177 240
P-Screen eb 3d 63, 166 229

The following table is just one suggestion for signatures that could be used. It uses bytes starting with the instruction that contains the pointer to the payload data. (This pointer is different in all known versions, and it also ought to make false positives from unrelated COM files highly unlikely.)

Type Sig. offs. Sig. bytes
0 117 8d 36 b0 01 fc 57 8b 0e 05 01 80 3e
1 34 be 5e 01 8b 0e 04 01 fc bb 00 b0 3c
2 104 be f0 01 ba da 03 b3 09 8b 0e 04 01
P-Screen 117 be e5 01 fc 57 8b 0e 05 01 80 3e 03

[edit] Specifications

  • An overview of the decompression algorithm for type 2 is in the UNCRUNCH.PAS file included with TheDraw 4.x.

[edit] Software

(Or just execute the file in a DOS environment.)

[edit] Sample files

Examples of modified files:

Retrieved from "http://fileformats.archiveteam.org/index.php?title=TheDraw_COM_File&oldid=51468"
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