MS-DOS installation compression

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|pronom={{PRONOM|fmt/462}}<br>{{PRONOM|fmt/469}}
 
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A pair of compression formats by Microsoft that appear on MS-DOS and early Windows (3.x) installation disks; the formats have no generally agreed-upon name. Compressed files may be generated by the COMPRESS.EXE program (appearing in Microsoft's Setup Toolkit for Visual C++), and uncompressed with the EXPAND.EXE program distributed with Windows and MS-DOS. Compressed files have the last character of the file extension replaced with an underscore (or dollar sign).
  
The '''MS-DOS installation compression''' system is used for system installation files when installing or upgrading MS-DOS starting with version 5.0a. It replaces the last character of the file extension with an underscore. The EXPAND command decompresses the files, and is run as part of the installer. Apparently the Google Chrome installation process [http://festiva-yourchoice.blogspot.com/2010/01/expandexe-preventing-google-chrome-from.html also needs it].
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There are reports of the Google Chrome installer [http://festiva-yourchoice.blogspot.com/2010/01/expandexe-preventing-google-chrome-from.html needing the EXPAND.EXE program].
 
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This format (usually?) uses [[LZ77]] compression.
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== Identification ==
 
== Identification ==
File begin with bytes <code>53 5A 44 44 88 F0 27 33</code>, or (rarely?) <code>4B 57 41 4A 88 F0 27 D1</code>.
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File begin with bytes <code>53 5A 44 44 88 F0 27 33</code> ("SZDD" variant), or <code>4B 57 41 4A 88 F0 27 D1</code> ("KWAJ" variant).
  
 
== Software ==
 
== Software ==
 
* EXPAND.EXE - utility included with many versions of MS Windows and MS-DOS
 
* EXPAND.EXE - utility included with many versions of MS Windows and MS-DOS
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* [ftp://ftp.microsoft.com/softlib/mslfiles/CP0982.EXE Setup Toolkit for Visual C++]
 
* [http://www.7-zip.org/ 7-Zip]
 
* [http://www.7-zip.org/ 7-Zip]
 
* [ftp://ftp.penguin.cz/pub/users/mhi/mscompress/ mscompress] - msexpand
 
* [ftp://ftp.penguin.cz/pub/users/mhi/mscompress/ mscompress] - msexpand
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== Links ==
 
== Links ==
 
* [http://support.microsoft.com/kb/80751 Documentation in Microsoft site]
 
* [http://support.microsoft.com/kb/80751 Documentation in Microsoft site]
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* [http://www.cabextract.org.uk/libmspack/doc/szdd_kwaj_format.html SZDD and KWAJ formats description]
  
 
[[Category:Microsoft]]
 
[[Category:Microsoft]]

Revision as of 23:31, 9 March 2015

File Format
Name MS-DOS installation compression
Ontology
Extension(s) .??_
PRONOM fmt/462
fmt/469

A pair of compression formats by Microsoft that appear on MS-DOS and early Windows (3.x) installation disks; the formats have no generally agreed-upon name. Compressed files may be generated by the COMPRESS.EXE program (appearing in Microsoft's Setup Toolkit for Visual C++), and uncompressed with the EXPAND.EXE program distributed with Windows and MS-DOS. Compressed files have the last character of the file extension replaced with an underscore (or dollar sign).

There are reports of the Google Chrome installer needing the EXPAND.EXE program.

Identification

File begin with bytes 53 5A 44 44 88 F0 27 33 ("SZDD" variant), or 4B 57 41 4A 88 F0 27 D1 ("KWAJ" variant).

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