Realia Spacemaker
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It compresses [[DOS executable (.com)|COM]] files (to COM), and [[MS-DOS EXE|EXE]] files (to EXE or COM). | It compresses [[DOS executable (.com)|COM]] files (to COM), and [[MS-DOS EXE|EXE]] files (to EXE or COM). | ||
| + | |||
| + | == Discussion == | ||
| + | Two versions have been found: 1.03 and 1.06. They create files that are slightly different. All compressed files found in the wild seem to be consistent with having been made by one of these two versions. | ||
| + | |||
| + | For an EXE file to be compressible by Spacemaker, it should have the following properties: | ||
| + | * The header field at offset 12, "max allocation", must be 0xffff. | ||
| + | * The header field at offset 26 must be 0. | ||
| + | * No overlay. | ||
== Identification == | == Identification == | ||
| − | ( | + | For COM format, the first 18 bytes match the pattern: |
| + | |||
| + | 9c 55 56 8c cd 83 c5 10 8d b6 ?? ?? 56 be ?? ?? | ||
| + | 56 cb | ||
| + | |||
| + | In pristine files, this is followed by the ASCII string "{{magic|MEMORY$}}". | ||
| + | |||
| + | For EXE format, the same pattern appears at the start of the ''code image'' segment (refer to [[MS-DOS_EXE#Special file positions]]), which is probably always offset 512 in pristine files. | ||
| − | + | It is possible to distinguish between version 1.03 and 1.06. | |
| − | + | It is possible to determine the original format, COM or EXE. For instance, if the original format was EXE, there are 9 consecutive 0x90 bytes in the decompressor code. Exception: The "<code>/S</code>" option makes it impossible to tell that the original format was EXE. | |
== Software == | == Software == | ||
Revision as of 16:30, 7 March 2026
Realia Spacemaker (or just Spacemaker) is an executable compression utility for DOS, developed by Realia. It was possibly the first executable compression utility for DOS to be released.
It compresses COM files (to COM), and EXE files (to EXE or COM).
Contents |
Discussion
Two versions have been found: 1.03 and 1.06. They create files that are slightly different. All compressed files found in the wild seem to be consistent with having been made by one of these two versions.
For an EXE file to be compressible by Spacemaker, it should have the following properties:
- The header field at offset 12, "max allocation", must be 0xffff.
- The header field at offset 26 must be 0.
- No overlay.
Identification
For COM format, the first 18 bytes match the pattern:
9c 55 56 8c cd 83 c5 10 8d b6 ?? ?? 56 be ?? ?? 56 cb
In pristine files, this is followed by the ASCII string "MEMORY$".
For EXE format, the same pattern appears at the start of the code image segment (refer to MS-DOS_EXE#Special file positions), which is probably always offset 512 in pristine files.
It is possible to distinguish between version 1.03 and 1.06.
It is possible to determine the original format, COM or EXE. For instance, if the original format was EXE, there are 9 consecutive 0x90 bytes in the decompressor code. Exception: The "/S" option makes it impossible to tell that the original format was EXE.
Software
- Spacemaker v1.03:
- spacemkr.lzh
- archive of ftp.update.uu.se → pub/rainbow/msdos/misc/spacemkr.lzh
- at DiscMaster
- Spacemaker v1.06:
- ANORMAL's DOSEXE collections → DOSEXE Executable Tools Pack → packers/spacemaker.106-realia.rar
- At Vetusware
Sample files
- DATER11.ZIP → DATER.COM (v1.03 EXE→COM)
- DISK0191.ZIP → DVED.COM (v1.03 COM→COM)
- NHPLUS.ZIP → GETYN.COM (v1.03 EXE→COM)
- Shareware Grab-Bag → 090/dutils.arc (v1.06; some EXE→COM, some COM→COM)
- ck2.zip → C*.EXE (v1.03)
- canset11.zip → *.EXE (v1.06)
- dexvert samples — archive/spaceMakerPacked
Links
- Realia SpaceMaker, at the OS/2 Museum
- Advertisement in PC Magazine, Jan. 1983, p. 417
