Disk Express - Revision history

Jsummers: /* Software */

2026-01-08T18:10:09Z

‎Software

Jsummers: /* Identification */

2026-01-04T13:13:24Z

‎Identification

Jsummers at 12:59, 4 January 2026

2026-01-04T12:59:30Z

RSola: /* Structure */ CRC is not standard

2026-01-02T22:25:36Z

‎Structure: CRC is not standard

Jsummers at 16:35, 2 January 2026

2026-01-02T16:35:46Z

Jsummers: /* Structure */

2026-01-02T15:27:50Z

‎Structure

Jsummers: /* Structure */

2026-01-02T15:08:01Z

‎Structure

Sembiance: /* Sample files */

2026-01-02T13:59:40Z

‎Sample files

Jsummers: Category:Executable envelopes

2025-11-23T14:49:46Z

Category:Executable envelopes

RSola: /* Software */ Links for shareware versions 2.x

2025-04-20T02:03:05Z

‎Software: Links for shareware versions 2.x

@@ Line 138: / Line 138: @@
 * [{{CdTextfilesURL|swextrav4-4/os2utilf/dxp233.zip}} Disk eXPress v2.33]
 * [{{SACFTPURL|utildisk|dxp234.zip}} Disk eXPress v2.34]
 == Sample files ==

@@ Line 9: / Line 9: @@
 == Identification ==
-If the file is not executable, it begins with a 512-byte header. The first two bytes will be 'AS' and the third will be a version number, 0-2.
+If the file is not executable, it begins with a 512-byte header. The first two bytes will be 'AS' and the third will be a version number: 1-2, but presumably always 2 for non-executable files.
 If the file is executable, it starts with an [[MS-DOS EXE]] header. Bytes 2-5 of the header give the length of the executable portion, as normal. The disk image header starting with 'AS' is found four bytes after the executable portion.
 Executable files use the .EXE extension.
 == File structure and format details ==

@@ Line 15: / Line 15: @@
 Executable files use the .EXE extension.
-== Structure ==
+== File structure and format details ==
 === Executable loader ===
@@ Line 24: / Line 24: @@
 * Hybrid of MS-DOS and OS/2 formats, for v2.00-2.34 (default format)
-The MS-DOS EXE loader is compressed with [[LZEXE]] for v1.01-1.02, or [[DIET (compression)|DIET]] (maybe with some hacks) for v1.96+. This is true even for the MS-DOS part of hybrid files. The OS/2 loader never uses executable compression.
+The MS-DOS EXE loader is compressed with [[LZEXE]] for v1.01-1.02, or [[DIET (compression)|DIET]] (maybe with special processing) for v1.96+. This is true even for the MS-DOS part of hybrid files. The OS/2 loader never uses executable compression.
 The loader is followed by a 4-byte CRC of the loader itself (including both DOS and OS/2 sections on a hybrid loader) and then the disk image data.
 Disk Express implements a variant of [[CRC-32#CRC-32/JAMCRC|CRC-32/JAMCRC]]. Only the initialization value is different.
 * On ordinary versions, the initialization value is <code>0x59d</code>. In some contexts, its bit-reversed (reflected) value <code>0xb9a00000</code> might appear or need to be used instead. The CRC of ASCII "<code>123456789</code>" would be <code>0x5ec78685</code>.
@@ Line 43: / Line 44: @@
 |0x000 || 2 bytes || Magic number, <code>AS</code>
 |-
-|0x002 || 1 byte  ||rowspan="2"| [Major version, minor version] of Disk Express required to write this file. Usually [1,1] in files generated by v1.01-1.02. Usually [2,0] in files made by v1.96+, or [2,30] if the 'encrypted' or 'bad sectors' flags are set.
+|0x002 || 1 byte  ||rowspan="2"| [Major version, minor version] of Disk Express required to write this file. Usually [1,1] in files generated by v1.01-1.02. [1,4] also exists, at least in some IBM-licensed files. Usually [2,0] in files made by v1.96+, or [2,30] if the 'encrypted' or 'bad sectors' flags are set.
 |-
 |0x003 || 1 byte
@@ Line 71: / Line 72: @@
 |}
 |-
-|0x006 || 4 bytes || CRC of disk data (before compression if compressed).
+|0x006 || 4 bytes || CRC of disk data. For compressed v1.0x files, the CRC is of the compressed data, excluding the 'length' fields. For compressed v1.96+ files, the CRC is calculated before compression.
 |-
 |0x00A || 1 byte  || Compression type:
@@ Line 124: / Line 125: @@
 == Software ==
-* [{{CdTextfilesURL|640swstudio/UTILITY/DKEXP101.ZIP}} Disk eXPress v1.01]
+* [{{CdTextfilesURL|640swstudio/UTILITY/DKEXP101.ZIP}} Disk Express v1.01]
-* [{{CdTextfilesURL|nopv07/020A/DKEXP1.ZIP}} Disk eXPress v1.02]
+* [{{CdTextfilesURL|nopv07/020A/DKEXP1.ZIP}} Disk Express v1.02]
-* {{DiscMasterLink|browse/14387/winos2_a.zip/winos2_a/OS2/UTILITY/DISK/DXP196B.ZIP|Disk eXPress v1.96 (beta)}}
+* {{DiscMasterLink|browse/14387/winos2_a.zip/winos2_a/OS2/UTILITY/DISK/DXP196B.ZIP|Disk Express v1.96 (beta)}}
 * {{DiscMasterLink|browse/21352/La_Coleccion_Walnut_Creek_Junio_1993.iso/dos/diskette/dxp200.zip|Disk eXPress v2.00}}
 * [{{CdTextfilesURL|pier01/017a/dxp203.zip}} Disk eXPress v2.03]

@@ Line 26: / Line 26: @@
 The MS-DOS EXE loader is compressed with [[LZEXE]] for v1.01-1.02, or [[DIET (compression)|DIET]] (maybe with some hacks) for v1.96+. This is true even for the MS-DOS part of hybrid files. The OS/2 loader never uses executable compression.
-The loader is followed by a 4-byte checksum and then the disk image data.
+The loader is followed by a 4-byte CRC of the loader itself (including both DOS and OS/2 sections on a hybrid loader) and then the disk image data.
 === Disk image header ===
@@ Line 67: / Line 71: @@
 |}
 |-
-|0x006 || 4 bytes || [[CRC-32]] of disk data (before compression if compressed). ''[But what algorithm? It's either not the usual one, or it's not used in the obvious way.]''
+|0x006 || 4 bytes || CRC of disk data (before compression if compressed).
 |-
 |0x00A || 1 byte  || Compression type:
@@ Line 105: / Line 109: @@
 |0x014 || 284 bytes || Always 0
 |-
-|0x130 || 4 bytes || CRC-32 of file header
+|0x130 || 4 bytes || CRC of file header
 |-
 |0x134 || 200 bytes || File description: 5 lines each of 40 characters, [[CP437]] character set
 |-
-|0x1FC || 4 bytes || CRC-32 of description
+|0x1FC || 4 bytes || CRC of description
 |}

@@ Line 5: / Line 5: @@
 |released=1991
 }}
+'''Disk Express''' (stylized as '''Disk eXPress''' (v2.x); short name: '''DSKEXP''' (v1.x) or '''DXP''' (v2.x)) is a floppy disk imaging utility for DOS and OS/2 by Albert J. Shan. It was released mainly as shareware. A disk image can be saved either as a data file (supported by v1.96+), or as an executable that when run writes its contents back to diskette (supported by all versions).
-'''Disk Express''' (stylized as '''Disk eXPress''') is a shareware utility for PCDOS and OS/2 by Albert J. Shan, allowing floppy disks to be imaged. A disk image could be saved either as a data file, or as an executable that when run wrote its contents back to diskette.
 == Identification ==
@@ Line 68: / Line 67: @@
 |}
 |-
-|0x006 || 4 bytes || [[CRC-32]] of disk data. ''[But what algorithm? It's either not the usual one, or it's not used in the obvious way.]''
+|0x006 || 4 bytes || [[CRC-32]] of disk data (before compression if compressed). ''[But what algorithm? It's either not the usual one, or it's not used in the obvious way.]''
 |-
 |0x00A || 1 byte  || Compression type:

@@ Line 33: / Line 33: @@
 |0x000 || 2 bytes || Magic number, <code>AS</code>
 |-
-|0x002 || 1 byte  || Major version of Disk Express required to write this file (2 in files generated by v2.x)
+|0x002 || 1 byte  ||rowspan="2"| [Major version, minor version] of Disk Express required to write this file. Usually [1,1] in files generated by v1.01-1.02. Usually [2,0] in files made by v1.96+, or [2,30] if the 'encrypted' or 'bad sectors' flags are set.
 |-
-|0x003 || 1 byte  || Minor version required to write this file (30 if 'encrypted' or 'bad sectors' flags are set, otherwise 0)
+|0x003 || 1 byte
 |-
 |0x004 || 1 byte  || Release of Disk Express that created this file (single ASCII character)
@@ Line 63: / Line 63: @@
 |0x006 || 4 bytes || [[CRC-32]] of disk data
 |-
-|0x00A || 1 byte  || Compression type: 0 for uncompressed, 1-2 for compressed
+|0x00A || 1 byte  || Compression type:
 |-
 |0x00B || 1 byte  || Last cylinder imaged

@@ Line 119: / Line 119: @@
 == Sample files ==
 Self-extracting images created by regular shareware and licensed versions
 * https://dl.dell.com/chipset/Kniea001.exe → DD0377p1.EXE, DD0377p2.EXE
 * https://ftpmirror.infania.net/sites/ct_treiber_service/treiber/toshiba/dos_driv/tcm30.exe → TCM3DISK.EXE - Encrypted image
 Self-extracting images created by special versions licensed for IBM
 * {{CdTextfilesURL|pier/pier03/035/vp162fix.zip}} → VP162FIX.EXE
 * http://phoenix.bnbbbs.net/files/os2swbbs/ndrivers/164adap2.exe
 Standalone disk images
 * [https://archive.org/download/2015.02.old-dos.ru 2015.02.old-dos.ru] → 2015.02.maxxx.tar → maxxx/DOS/System/DRdos/Drdos50/4dxp/DRD50-*.DXP - Uncompressed, version 2.x
 [[Category:Executable envelopes]]

← Older revision		Revision as of 14:49, 23 November 2025
Line 133:		Line 133:

	* [https://archive.org/download/2015.02.old-dos.ru 2015.02.old-dos.ru] → 2015.02.maxxx.tar → maxxx/DOS/System/DRdos/Drdos50/4dxp/DRD50-*.DXP - Uncompressed, version 2.x		* [https://archive.org/download/2015.02.old-dos.ru 2015.02.old-dos.ru] → 2015.02.maxxx.tar → maxxx/DOS/System/DRdos/Drdos50/4dxp/DRD50-*.DXP - Uncompressed, version 2.x
		+
		+	[[Category:Executable envelopes]]