SCRNCH - Revision history

Jsummers: /* Software */

2025-01-07T18:26:36Z

‎Software

Jsummers at 16:03, 7 January 2025

2025-01-07T16:03:21Z

Jsummers at 21:10, 2 January 2025

2025-01-02T21:10:36Z

Jsummers: /* Software */

2025-01-02T15:49:20Z

‎Software

Jsummers at 15:39, 2 January 2025

2025-01-02T15:39:27Z

Jsummers at 15:22, 2 January 2025

2025-01-02T15:22:29Z

Jsummers at 19:42, 10 October 2021

2021-10-10T19:42:13Z

Jsummers at 19:37, 10 October 2021

2021-10-10T19:37:58Z

Jsummers at 18:07, 10 October 2021

2021-10-10T18:07:57Z

Jsummers at 17:20, 10 October 2021

2021-10-10T17:20:57Z

@@ Line 41: / Line 41: @@
 * {{CdTextfiles|carousel/013C/SCRNCH.ZIP|SCRNCH v1.00}} (1988-01-31)
 * {{CdTextfiles|simtel/simtel9510/disk2/DISC2/COMPRESS/SCRNC102.ZIP|SCRNCH v1.02}} (1988-03-28 / 1988-04-04)
-* [{{SACFTPURL|pack|dese2b10.zip}} DeSCRE2B] - DOS utility to help decompress SCRNCHed EXE files
+* [{{SACFTPURL|pack|dese2b10.zip}} DeSCRE2B] - DOS utility to help decompress SCRNCHed files that were originally in EXE format
 See [[Executable compression#Decompression software]] for some multi-format utilities that might be able to decompress Run Mode files. (See also the [[SCRE2B]] article.)

@@ Line 12: / Line 12: @@
 Run Mode compresses a [[DOS executable (.com)|COM]] file to a COM or (for v1.02) [[MS-DOS EXE|EXE]] file.
-SCRNCH also provides a way to compress EXE files (to COM or EXE), with help from the included [[SCRE2B]] utility, though this is separate from the main SCRNCH utility.
+SCRNCH also provides a way to compress EXE files (to COM or EXE), with help from the included [[SCRE2B]] utility. This is not part of the main SCRNCH utility, though there is an included COMPRESS.BAT script to automate the process.
 Write Mode compresses a file that is generally not executable, to a COM or EXE file. In the simplest case, it converts a text file to an executable file that prints the text to the screen. With effort, it can do other things, such as ask the user for a filename, then write the decompressed data to that file.
@@ Line 32: / Line 32: @@
 For COM format, the signature is at the start of the file. For EXE, it's at the start of the ''code image'' segment (refer to [[MS-DOS EXE#Special file positions]]), which is normally at offset 512.
-Considering that SCRNCH plays fast and loose with converting between COM and EXE formats, one should probably assume that all six signatures could appear in both COM and EXE files.
+Considering that SCRNCH plays fast and loose with converting between COM and EXE formats, it may be possible that all six signatures could appear in both COM and EXE files.
 == Related formats ==
@@ Line 47: / Line 47: @@
 Write Mode files can decompress themselves. In a DOS environment, run the file with the special "<code>stdout</code>" parameter, with output redirected to a file. For example, using the SCRNCH documentation file:
-  &gt;SCRDOC.COM stdout &gt; SCRDOC.DOC
+  SCRDOC.COM stdout &gt; SCRDOC.DOC
 == Sample files ==
@@ Line 63: / Line 63: @@
 * {{CdTextfiles|gigabytesw/030a/grab57.zip|grab57.zip}} → README.COM
 * {{CdTextfiles|gigabytesw/030a/prodev1.zip|prodev1.zip}} → PRICEDOC.EXE
 Various:
 * SCRNCH.COM and SCRDOC.COM from the SCRNCH distribution

@@ Line 5: / Line 5: @@
 |released=1988
 }}
-'''SCRNCH''' is an executable compression utility for DOS. It was developed by Graeme W. McRae, and distributed as shareware.
+'''SCRNCH''' is a data compression utility and toolkit for DOS. It was developed by Graeme W. McRae, and distributed as shareware.
 == Discussion ==
-SCRNCH is fundamentally a [[DOS executable (.com)|COM]] file compressor, but it includes tools and features that make it possible to compress [[MS-DOS EXE|EXE]] files, by converting them to a COM or COM-like format that SCRNCH can compress, then back to EXE if desired.
+Run Mode compresses a [[DOS executable (.com)|COM]] file to a COM or (for v1.02) [[MS-DOS EXE|EXE]] file.
-SCRNCH's default COM-to-(COM or EXE) compression mode is called "Run Mode". It also has a mode it calls "Write Mode", which essentially creates self-decompressing files. In the simplest case, Write Mode converts a text file to an executable file that prints the text to the screen. With effort, it can be used for other things, like software installation.
+SCRNCH also provides a way to compress EXE files (to COM or EXE), with help from the included [[SCRE2B]] utility, though this is separate from the main SCRNCH utility.
-SCRNCH v1.02 supports EXE-format output (but not input) in both modes. V1.00 supports EXE output only in Write Mode.
+Write Mode compresses a file that is generally not executable, to a COM or EXE file. In the simplest case, it converts a text file to an executable file that prints the text to the screen. With effort, it can do other things, such as ask the user for a filename, then write the decompressed data to that file.
 == Identification ==

@@ Line 40: / Line 40: @@
 * {{CdTextfiles|simtel/simtel9510/disk2/DISC2/COMPRESS/SCRNC102.ZIP|SCRNCH v1.02}} (1988-03-28 / 1988-04-04)
 * [{{SACFTPURL|pack|dese2b10.zip}} DeSCRE2B] - DOS utility to help decompress SCRNCHed EXE files
 == Sample files ==

← Older revision		Revision as of 15:39, 2 January 2025
Line 40:		Line 40:
	* {{CdTextfiles\|simtel/simtel9510/disk2/DISC2/COMPRESS/SCRNC102.ZIP\|SCRNCH v1.02}} (1988-03-28 / 1988-04-04)		* {{CdTextfiles\|simtel/simtel9510/disk2/DISC2/COMPRESS/SCRNC102.ZIP\|SCRNCH v1.02}} (1988-03-28 / 1988-04-04)
	* [{{SACFTPURL\|pack\|dese2b10.zip}} DeSCRE2B] - DOS utility to help decompress SCRNCHed EXE files		* [{{SACFTPURL\|pack\|dese2b10.zip}} DeSCRE2B] - DOS utility to help decompress SCRNCHed EXE files
		+
		+	== Sample files ==
		+	v1.00 Run Mode:
		+	* {{CdTextfiles\|gigabytesw/010b/sayclear.zip\|sayclear.zip}} → SAY-DOC.COM
		+
		+	v1.02 Run Mode:
		+	* {{CdTextfiles\|gigabytesw/027a/em87.zip\|em87.zip}} → EM87.COM
		+	* {{CdTextfiles\|simtel0692/MSDOS/DBASE/PCF501C.ZIP\|PCF501C.ZIP}} → D0C.COM
		+	* {{CdTextfiles\|smsharew/GENERAL/STARWARS.ZIP\|STARWARS.ZIP}} → HARDCOPY.EXE
		+	* {{CdTextfiles\|simtel0692/MSDOS/DBASE/PCF501B.ZIP\|PCF501B.ZIP}} → DBRPT.EXE, FCONVERT.EXE, PCPACK.EXE
		+
		+	v1.02 Write Mode:
		+	* {{CdTextfiles\|pcsig12/CLA/DISK1769.ZIP\|DISK1769.ZIP}} → README.COM
		+	* {{CdTextfiles\|gigabytesw/030a/grab57.zip\|grab57.zip}} → README.COM
		+	* {{CdTextfiles\|gigabytesw/030a/prodev1.zip\|prodev1.zip}} → PRICEDOC.EXE
		+
		+	Various:
		+	* SCRNCH.COM and SCRDOC.COM from the SCRNCH distribution

@@ Line 8: / Line 8: @@
 == Discussion ==
-SCRNCH is fundamentally a [[DOS executable (.com)|COM]] file compressor, but it includes tools and features that make it possible to compress [[MS-DOS EXE|EXE]] files, by converting them to a COM or COM-like format that SCRNCH can compress, then back to EXE if necessary.
+SCRNCH is fundamentally a [[DOS executable (.com)|COM]] file compressor, but it includes tools and features that make it possible to compress [[MS-DOS EXE|EXE]] files, by converting them to a COM or COM-like format that SCRNCH can compress, then back to EXE if desired.
 SCRNCH's default COM-to-(COM or EXE) compression mode is called "Run Mode". It also has a mode it calls "Write Mode", which essentially creates self-decompressing files. In the simplest case, Write Mode converts a text file to an executable file that prints the text to the screen. With effort, it can be used for other things, like software installation.
@@ Line 15: / Line 15: @@
 == Identification ==
-(Based on limited testing.)
+SCRNCH v1.00-compressed COM files (both modes) start with bytes {{magic|bb ff ff b4 4a cd 21 81 eb}}. The modes can be distinguished. For example, the byte at offset 37 seems to be <code>0x8c</code> for Run Mode, or <code>0xfc</code> for Write Mode.
-SCRNCH v1.00-compressed COM files (both modes) start with bytes {{magic|bb ff ff b4 4a cd 21 81 eb}}.
+SCRNCH v1.00-compressed EXE files (which must be Write Mode) have {{magic|bb ff ff b4 4a cd 21 81 eb}} at offset 512.
-SCRNCH v1.02-compressed COM files, Run Mode, start with {{magic|eb 13 's' 'C' 'e' 'f'}}.
+Based on analysis of the (decompressed) SCRNCH.COM file, a v1.02 SCRNCHed file contains one of six possible "signature" byte sequences:
-SCRNCH v1.02-compressed COM files, Write Mode, start with {{magic|eb 13 's' 'C' 'w' 'f'}}.
+ eb 13 73 43 65 66 0c 03 ("sCef"): Run Mode, default for COM output
-SCRNCH v1.02-compressed COM files, both modes, also have {{magic|bb ff ff b4 4a cd 21 81 eb}} at offset 21.
+For COM format, the signature is at the start of the file. For EXE, it's at the start of the ''code image'' segment (refer to [[MS-DOS EXE#Special file positions]]), which is normally at offset 512.
-SCRNCH v1.00-compressed EXE files (Write Mode) have {{magic|bb ff ff b4 4a cd 21 81 eb}} at offset 512.
+Considering that SCRNCH plays fast and loose with converting between COM and EXE formats, one should probably assume that all six signatures could appear in both COM and EXE files.
-−
-SCRNCH v1.02-compressed EXE files, Run Mode, have {{magic|eb 13 's' 'C' 'h' 'f'}} at offset 512.
-−
-SCRNCH v1.02-compressed EXE files, Write Mode, have {{magic|eb 13 's' 'C' 'y' 'f'}} at offset 512.
 == Related formats ==
 * [[ZIP]] - Reportedly[{{CdTextfilesURL|rbbsv3n1/pool/pkpolicy.zip}}], ZIP's ''Reduce'' compression method is based on SCRNCH's compression method.
@@ Line 37: / Line 39: @@
 * {{CdTextfiles|carousel/013C/SCRNCH.ZIP|SCRNCH v1.00}} (1988-01-31)
 * {{CdTextfiles|simtel/simtel9510/disk2/DISC2/COMPRESS/SCRNC102.ZIP|SCRNCH v1.02}} (1988-03-28 / 1988-04-04)
-* [{{SACFTPURL|pack|dese2b10.zip}} DeSCRE2B] - Utility to help decompress SCRNCHed EXE files
+* [{{SACFTPURL|pack|dese2b10.zip}} DeSCRE2B] - DOS utility to help decompress SCRNCHed EXE files

@@ Line 10: / Line 10: @@
 SCRNCH is fundamentally a [[DOS executable (.com)|COM]] file compressor, but it includes tools that make it possible to compress [[MS-DOS EXE|EXE]] files, using a convoluted method of converting them to a COM or COM-like format that SCRNCH can compress, then back to EXE if necessary.
-SCRNCH also has a feature it calls "write mode", which essentially creates self-decompressing files. In the simplest case, it converts a text file to a COM file that, when executed, prints the text to the screen. With effort, it can be used for other things, like software installation.
+SCRNCH's default COM-to-COM compression mode is called "Run Mode". It also has a mode it calls "Write Mode", which essentially creates self-decompressing files. In the simplest case, Write Mode converts a text file to a COM file that, when executed, prints the text to the screen. With effort, it can be used for other things, like software installation.
 == Identification ==
-''(TODO)''
+(Based on limited testing.)
 == Related formats ==