SCRNCH
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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. | 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. | ||
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| + | SCRNCH v1.02 also supports EXE-format output in both modes. V1.00 supports EXE output only in Write Mode. | ||
== Identification == | == Identification == | ||
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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 COM files (both modes) start with bytes {{magic|bb ff ff b4 4a cd 21 81 eb}}. | ||
| − | SCRNCH v1.02-compressed COM files, Run Mode, start with | + | SCRNCH v1.02-compressed COM files, Run Mode, start with {{magic|eb 13 's' 'C' 'e' 'f'}}. |
| − | SCRNCH v1.02-compressed COM files, Write Mode, start with | + | SCRNCH v1.02-compressed COM files, Write Mode, start with {{magic|eb 13 's' 'C' 'w' 'f'}}. |
SCRNCH v1.02-compressed COM files, both modes, also have {{magic|bb ff ff b4 4a cd 21 81 eb}} at offset 21. | SCRNCH v1.02-compressed COM files, both modes, also have {{magic|bb ff ff b4 4a cd 21 81 eb}} at offset 21. | ||
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| + | SCRNCH v1.00-compressed EXE files (Write Mode) have {{magic|bb ff ff b4 4a cd 21 81 eb}} at offset 512. | ||
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| + | SCRNCH v1.02-compressed EXE files, Run Mode, have {{magic|eb 13 's' 'C' 'h' 'f'}} at offset 512. | ||
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| + | SCRNCH v1.02-compressed EXE files, Write Mode, have {{magic|eb 13 's' 'C' 'y' 'f'}} at offset 512. | ||
== Related formats == | == Related formats == | ||
Revision as of 19:37, 10 October 2021
SCRNCH is an executable compression utility for DOS. It was developed by Graeme W. McRae, and distributed as shareware.
Contents[hide] |
Discussion
SCRNCH is fundamentally a COM file compressor, but it includes tools that make it possible to compress 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'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.
SCRNCH v1.02 also supports EXE-format output in both modes. V1.00 supports EXE output only in Write Mode.
Identification
(Based on limited testing.)
SCRNCH v1.00-compressed COM files (both modes) start with bytes bb ff ff b4 4a cd 21 81 eb.
SCRNCH v1.02-compressed COM files, Run Mode, start with eb 13 's' 'C' 'e' 'f'.
SCRNCH v1.02-compressed COM files, Write Mode, start with eb 13 's' 'C' 'w' 'f'.
SCRNCH v1.02-compressed COM files, both modes, also have bb ff ff b4 4a cd 21 81 eb at offset 21.
SCRNCH v1.00-compressed EXE files (Write Mode) have bb ff ff b4 4a cd 21 81 eb at offset 512.
SCRNCH v1.02-compressed EXE files, Run Mode, have eb 13 's' 'C' 'h' 'f' at offset 512.
SCRNCH v1.02-compressed EXE files, Write Mode, have eb 13 's' 'C' 'y' 'f' at offset 512.
Related formats
Software
- SCRNCH v1.00 (1988-01-31)
- SCRNCH v1.02 (1988-03-28 / 1988-04-04)
- DeSCRE2B - Utility to help decompress SCRNCHed EXE files
