Ready, Set, Go!

Posted on by Thor Leave a comment

By the title you might think this was a post about racing. But this is a file format blog, so we will keep on that topic. When I was in school many years ago, I remember using desktop publishing tools like PageMaker for the first time. When I got a job working for a local commercial printer in the early 1990’s, I was introduced to QuarkXPress. This became a career and I spent the next decade and a half working in the PrePress field. I got to know tools like Quark and InDesign extremely well. But even before these layout tools became what they are today, there was an early entry into the desktop publishing market.

Ready, Set, Go! was the “Ultimate Page Processor” released in 1985 for the Macintosh by Manhattan Graphics Corp. But had started advertising as early as Summer 1984.

For a few years it was one of the best layout tools on the market and was not very expensive. It continued to add features which rivaled the more expensive tools. Aldus PageMaker also come out shortly after in 1985, but was almost $500 when released. The software was sold to Letraset in 1987 and used it to replace their MacPublisher/LetraPage product and shortly afterwards released version 4.0 of Ready, Set, Go!. Letraset made some improvements and even tried to make a pro version called DesignStudio in 1989. When sales started to stagnate and Tools like Pagemaker and Quark owning most of the market, Letraset gave the software back to Manhattan Graphics in the USA in 1992 who then released a small update combining the two products back together into version 5.0. Then they released version 6.0 later that year. In 1996 the international rights were sold to Diwan, a company who could make use of the very foreign language capabilities of the software.

Ready, Set, Go! had a great history of foreign language support, thanks in part to the Apple Quickdraw GX software which helped render other language glyphs and writing directions. There were special versions for languages like Hebrew. A GX version of the software was released in 1996 that supported many other languages.

Because of and in spite of the craziness of the software’s ownership, the file format used with the software changed frequently, but mostly kept the same basic structure. Identification of the different versions will be difficult, but that is why we are here, let’s take a look. Remember, these were all very early Macintosh programs, meaning there is no extension and their identification is based on Type/Creator codes. Luckily, there is no Resource Forks we need to account for in their identification or preservation.

Here is a look at a file from version 1.

 % hexdump -C RSG1-s01 | head
00000000  00 78 00 03 00 00 00 48  00 48 00 00 00 00 02 da  |.x.....H.H......|
00000010  02 28 ff e1 ff e2 02 f9  02 46 03 47 05 28 03 fc  |.(.......F.G.(..|
00000020  00 02 00 00 00 48 00 48  00 00 00 00 02 da 02 28  |.....H.H.......(|
00000030  00 01 00 00 00 64 00 00  00 01 00 01 01 01 00 00  |.....d..........|
00000040  00 01 27 0f 00 01 00 01  00 00 00 00 00 00 00 00  |..'.............|
00000050  00 00 00 00 00 02 00 19  01 90 00 00 00 00 00 40  |...............@|
00000060  00 00 00 00 00 00 00 00  00 01 00 00 00 00 00 00  |................|
00000070  00 00 00 00 00 00 00 00  00 00 00 01 00 01 00 48  |...............H|
00000080  00 48 00 48 00 48 00 01  00 00 00 01 00 00 00 01  |.H.H.H..........|
00000090  00 00 00 01 00 00 00 00  00 00 00 00 00 00 00 00  |................|

% hexdump -C RSG2-s01 | head
00000000  00 78 00 02 00 00 00 48  00 48 00 00 00 00 02 d8  |.x.....H.H......|
00000010  02 28 ff e0 ff e2 02 f8  02 46 03 07 05 28 03 fc  |.(.......F...(..|
00000020  00 02 00 00 00 48 00 48  00 00 00 00 02 d8 02 28  |.....H.H.......(|
00000030  00 01 00 00 00 64 00 00  00 01 00 01 01 01 00 00  |.....d..........|
00000040  00 01 27 0f 00 01 00 01  00 00 00 00 00 00 00 00  |..'.............|
00000050  00 00 00 00 00 02 00 19  01 90 00 00 00 00 00 00  |................|
00000060  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000070  00 00 00 00 00 00 00 00  00 00 00 01 00 13 00 04  |................|
00000080  00 10 00 1c 00 04 00 10  00 10 00 01 00 01 00 00  |................|
00000090  00 03 17 54 00 06 14 9e  00 05 08 ae 00 01 50 ec  |...T..........P.|

% getfileinfo RSG2-s01
file: "RSG2-s01"
type: "RSGI"
creator: "MART"
attributes: avbstclInmedz
created: 04/17/1986 17:31:32
modified: 04/28/1986 10:53:01

% hexdump -C RSG3 | head
00000000  00 1e 00 00 00 86 00 01  b8 2a 00 01 00 03 00 02  |.........*......|
00000010  00 01 b8 12 00 01 b8 1e  00 01 b8 4e 00 00 00 01  |...........N....|
00000020  b8 0a 00 00 80 00 00 00  80 00 00 00 80 00 00 00  |................|
00000030  80 00 00 00 40 00 00 00  40 00 00 04 00 02 00 01  |....@...@.......|
00000040  b8 06 ff fd 52 53 47 33  00 6c 65 64 00 ff ff f0  |....RSG3.led....|
00000050  1f ff ff f0 1f ff ff f0  00 00 00 10 00 00 34 42  |..............4B|
00000060  41 50 50 4c 00 00 00 ff  00 00 00 10 00 00 00 22  |APPL..........."|
00000070  44 52 57 47 00 01 00 ff  00 00 00 10 00 00 00 00  |DRWG............|
00000080  00 10 43 54 00 02 00 01  ff 00 ff ff 00 00 00 78  |..CT...........x|
00000090  00 03 00 00 00 48 00 48  00 00 00 00 02 f0 02 40  |.....H.H.......@|

% hexdump -C RSG4-s01 | head
00000000  01 90 00 00 01 e6 00 00  01 e2 00 00 00 00 00 00  |................|
00000010  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00000060  00 00 00 00 00 00 00 cc  00 04 5b a0 00 01 00 03  |..........[.....|
00000070  00 02 00 04 5b 68 00 04  5b 70 00 04 5b 7c 00 00  |....[h..[p..[|..|
00000080  00 04 5b 5c 00 00 00 04  5b 64 00 00 80 00 00 00  |..[\....[d......|
00000090  80 00 00 00 80 00 00 00  80 00 00 00 40 00 00 00  |............@...|
000000a0  40 00 00 04 00 02 ff 00  00 04 5b 60 ff fe 08 52  |@.........[`...R|
000000b0  53 47 34 2d 73 30 31 00  00 00 00 00 00 00 00 00  |SG4-s01.........|
000000c0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|

% getfileinfo RSG4.5 
file: "RSG4.5"
type: "RSGR"
creator: "MEMR"
attributes: avbstclInmedz
created: 11/16/2021 13:39:34
modified: 11/16/2021 13:39:34

If you would like to play around with some samples from version 2. You can download them from here:

We can look at the hexadecimal for all the files, but this table will better explain the differences between versions.

VersionTypeCreatorFirst two BytesDeveloperYear
1.0.1RSGFMART0078Manhattan Graphics Corporation1985
2.0RSGIMART0078Manhattan Graphics Corporation1985
3.0RSGJMRSN001EManhattan Graphics Corporation1986
4.0RSGKMRSN0190Letraset1987
4.5RSGRMEMR138BLetraset1988
Design Studio 1.0RSGSMRJN13C9Letraset1989
Design Studio 2.0DSTDMRJN13E4Letraset1991
6.0.2MG6FMROS1770Manhattan Graphics1993
7.0.5 IntlMG7FMRDN1B61Diwan1996
7.2.8MG6FMROS1BBCDiwan2002
7.7.8MG6FMROS1BBCDiwan2011

This table is what I know currently, there is probably many more I can add as I locate samples, such as Version 5.0 and 5.1.

It amazes me how often the Creator code changes, usually this is fairly stable, but since it did change hands a lot, it makes a little sense. The Type code can often indicate changes in file format, so we can see version 1 & 2 are probably compatible, and later versions 6 & 7, but there own read me files helps us understand the compatibility. Version 2 added multiple page support, so it might have more differences.

Ready,Set,Go! 6.0 can open files created with Ready,Set,Go! 4.5, 4.5a, 5.0, and 5.1, and DesignStudio 1.0, 1.01 and 2.0. It cannot open files created with versions 1, 2, 3 or 4 of Ready,Set,Go! Registered users can obtain a special version of RSG 4.5 to open files created with earlier versions of Ready,Set,Go! to convert them to Version 6.0.

Ready,Set,Go! will open an old RSG document down to version 4 and a DesignStudio document down to version 1.0. Ready,Set,Go! 7.1 will automatically save it with the name ‘Copy of (filename)’ in order not to overwrite the old document. Whereas Ready,Set,Go! 7.2 or later can save documents that are compatible with Ready,Set,Go! versions 6 and 7.0.

So it seems you need version 4.5 to open earlier files and version 6 to open versions 4.5 to 5.1, then in 7.2 a change happened separating versions 6-7.1 and 7.2 and greater. Sounds like we will need at least 4 signatures to identify all the major changes.

Save As menu from version 7.2

Here is the problem, the main differences between the versions is the first two bytes. This is not enough to make a strong signature in PRONOM. Let look at some options. 

% hexdump -C RSG4-s01 | tail
00000160  00 00 02 da 02 28 00 01  00 00 00 64 00 00 00 01  |.....(.....d....|
00000170  00 01 01 01 00 00 00 01  27 0f 00 01 00 01 00 00  |........'.......|
00000180  00 00 00 00 00 00 00 00  00 00 00 02 00 19 01 90  |................|
00000190  00 00 00 00 00 40 00 00  00 00 00 00 00 00 00 01  |.....@..........|
000001a0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000001b0  00 00 00 2a 00 00 00 00  00 00 00 00 00 00 00 00  |...*............|
000001c0  00 01 00 00 00 00 00 00  00 00 00 00 00 00 00 01  |................|
000001d0  00 00 00 00 00 00 00 00  00 00 00 00 00 01 00 00  |................|
000001e0  00 00 00 00 00 00 00 00  00 00 ff ff ff ff ff ff  |................|

Many since version 3 end with at least two bytes of the values FF FF, but that is also pretty common.

% hexdump -C RSG4.5 | head
00000000  13 8b 00 00 04 10 00 00  04 0c 00 00 04 14 00 00  |................|
00000010  04 18 00 00 04 1c 00 00  00 00 00 00 00 00 00 00  |................|
00000020  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00000060  00 00 00 00 00 00 01 88  17 62 e1 d4 00 01 00 03  |.........b......|
00000070  00 02 17 62 e1 d0 17 62  e1 dc 17 62 e1 e8 00 00  |...b...b...b....|
00000080  17 62 e1 cc 00 00 17 62  e1 c8 00 00 80 00 00 00  |.b.....b........|
00000090  80 00 00 00 80 00 00 00  80 00 00 00 40 00 00 00  |............@...|
000000a0  40 00 00 04 00 02 ff 00  17 62 e1 50 ff fd 06 52  |@........b.P...R|
000000b0  53 47 34 2e 35 65 64 00  00 00 00 00 00 00 00 00  |SG4.5ed.........|

The header generally contains two bytes, then 00 00, then repeats for a few bytes, but adding 00 00 to a signature is also not very robust. Comparing version 3 to version 4 file doesn’t show much in common except for zeros. It may not be possible to combine signatures, they may need individual signatures for each version.

But the versions after 6, have an interesting segment of bytes. “050102030102060102030102060102030102060102030102060102030102070102090102070102030102070102090102070102090102070102090102070102090102060102030102060102030102060102030102060102030102050102030102050102030102050102030102050102030102050102030102050102030102060102030102050102030102050102030102050102030102”

% hexdump -C /Users/thorsted/Downloads/ReadySetGo\ \(1\)/RSG6       
00000000  17 70 00 00 34 70 00 00  34 6c 00 00 34 74 00 00  |.p..4p..4l..4t..|
00000010  34 78 00 00 34 90 00 00  34 a4 00 00 38 fe 00 00  |4x..4...4...8...|
00000020  39 20 00 00 39 68 00 00  3b 40 00 00 3b 44 00 00  |9 ..9h..;@..;D..|
00000030  3b 44 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |;D..............|
00000040  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
000001c0  00 03 01 01 00 ff 00 00  00 00 05 01 02 03 01 02  |................|
000001d0  06 01 02 03 01 02 06 01  02 03 01 02 06 01 02 03  |................|
000001e0  01 02 06 01 02 03 01 02  07 01 02 09 01 02 07 01  |................|
000001f0  02 03 01 02 07 01 02 09  01 02 07 01 02 09 01 02  |................|
00000200  07 01 02 09 01 02 07 01  02 09 01 02 06 01 02 03  |................|
00000210  01 02 06 01 02 03 01 02  06 01 02 03 01 02 06 01  |................|
00000220  02 03 01 02 05 01 02 03  01 02 05 01 02 03 01 02  |................|
00000230  05 01 02 03 01 02 05 01  02 03 01 02 05 01 02 03  |................|
00000240  01 02 05 01 02 03 01 02  06 01 02 03 01 02 05 01  |................|
00000250  02 03 01 02 05 01 02 03  01 02 05 01 02 03 01 02  |................|
00000260  00 09 20 60 00 08 80 00  00 0b 00 00 00 01 00 00  |.. `............|
00000270  00 02 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000280  00 00 00 00 00 ea 04 b0  00 64 03 e8 00 00 00 00  |.........d......|
00000290  17 97 50 6c 00 00 00 00  00 3c 00 3d 00 3e 00 3f  |..Pl.....<.=.>.?|
000002a0  00 40 00 41 00 42 00 43  00 64 00 05 00 00 00 00  |.@.A.B.C.d......|
000002b0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|

It is in all the samples I have for version 6+, most have the same 150 bytes, all starting around the 458th byte (0x1CA). I have no idea what it means, but it makes up for the weak bytes available in the older versions. If anyone out there knows the significance in this byte sequence, I would like to understand. Visually it looks the most interesting in a 3 column view, and some files do have one byte difference.

Ok, so for now, it looks like the best option is to group the signatures into Version 3-4, Version 6-7, and DesignStudio 1-2. I will look at what is best for Version 1-2 of ReadySetGo in the future. For now, you can see my samples and suggested signature on my GitHub page.

AutoSketch

Posted on by Thor 1 Comment

There was a lot of CAD programs in the 1980’s through the 1990’s. Some titles might be TurboCAD, DesignCAD, Generic CADD, KeyCAD, SwiftCAD, CADKEY, VersaCAD, MiniCAD, EasyCAD, and of course AutoCAD. Also, many file formats. Some had chosen the common DXF exchange format, but most chose their own way to do things.

AutoCAD is software made by AutoDesk, but is one of many software tools made by them. AutoCAD has its own native file format, DWG, as is well documented, but there was a little brother to AutoCAD marketed for a few years and it also had its own format(s).

AutoSketch was a less powerful version of AutoCAD and only supported 2D models, but still found a good following of users. Unlike its big brother, the AutoSketch native format(s) don’t have much documentation and are not supported in any AutoDesk product today. The PRONOM entry for the SKF (fmt/306) is missing a signature, it is an outline entry only. In addition, SKF, AutoSketch had an earlier format that needs to be documented and a signature created. Let’s take a look.

The first version of AutoSketch came out in 1986 for DOS and files stored in RAM which could be written out as a SKD file. Looking at a saved file, we see a very easy to identify file. 

% hexdump -C TEMPLATE.SKD | head
00000000  41 75 74 6f 53 6b 65 74  63 68 20 64 72 61 77 69  |AutoSketch drawi|
00000010  6e 67 20 64 61 74 61 62  61 73 65 0d 0a 1a 00 00  |ng database.....|
00000020  49 03 00 44 00 00 00 01  00 00 00 00 00 00 00 00  |I..D............|
00000030  00 00 00 00 00 40 41 00  00 10 41 00 00 00 00 00  |.....@A...A.....|
00000040  00 00 00 00 00 40 41 00  00 10 41 00 00 00 3f 01  |.....@A...A...?.|
00000050  00 09 00 00 00 00 00 00  00 00 00 00 00 00 00 33  |...............3|
00000060  33 33 33 33 33 d3 3f 00  00 00 00 00 00 f0 3f 00  |33333??......??.|
00000070  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000080  00 80 3f 00 00 80 3f 0a  00 08 00 00 00 00 00 ff  |..?...?........?|
00000090  ff 00 00 00 00 00 00 00  00 00 00 00 00 00 00 25  |?..............%|

Most formats don’t make it this easy. Having the ASCII string “AutoSketch drawing database” makes identification very easy. Lets see if this pattern stays true with the next version, version 2.0 for DOS.

% hexdump -C ENGINE.SKD | head
00000000  41 75 74 6f 53 6b 65 74  63 68 20 64 72 61 77 69  |AutoSketch drawi|
00000010  6e 67 20 64 61 74 61 62  61 73 65 0d 0a 1a 00 fd  |ng database....?|
00000020  49 06 00 12 04 00 00 01  00 00 00 64 20 88 40 f7  |I..........d .@?|
00000030  eb 38 c2 88 fe 1b 44 25  83 dd 43 00 00 00 00 00  |?8?.?.D%.?C.....|
00000040  00 00 00 00 80 1d 44 00  80 d9 43 00 00 00 41 01  |......D..?C...A.|
00000050  00 07 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000060  00 00 00 00 00 14 40 00  00 00 00 00 00 f0 3f 00  |......@......??.|
00000070  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000080  00 40 41 00 00 40 41 0a  00 08 00 00 00 00 00 1f  |.@A..@A.........|
00000090  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 1d  |................|

AutoDesk also released version 3.0 of AutoSketch in 1990.

Version 3.0 of AutoSketch produced files which appear very similar, but needs a closer look.

% hexdump -C ASSY.SKD | head
00000000  41 75 74 6f 53 6b 65 74  63 68 20 64 72 61 77 69  |AutoSketch drawi|
00000010  6e 67 20 64 61 74 61 62  61 73 65 0d 0a 1a 00 8b  |ng database.....|
00000020  49 09 00 db 00 00 00 01  00 00 00 00 00 00 00 00  |I..?............|
00000030  00 00 00 b7 cc a4 41 79  99 79 41 00 00 00 00 00  |...?̀¤Ay.yA.....|
00000040  00 00 00 00 00 04 42 00  00 90 41 00 00 00 3f 01  |......B...A...?.|
00000050  00 07 00 00 00 00 00 00  00 00 00 00 00 00 00 9a  |................|
00000060  99 99 99 99 99 c9 3f 00  00 00 00 00 00 f0 3f 00  |.....??......??.|
00000070  00 00 00 00 00 00 00 00  00 00 00 01 00 00 00 00  |................|
00000080  00 80 3f 00 00 80 3f 0a  00 08 00 00 00 00 00 ff  |..?...?........?|
00000090  00 00 00 00 00 00 00 00  00 33 33 33 33 33 f3 1e  |.........33333?.|
*
000001b0  00 00 00 00 00 f0 3f 01  00 01 00 00 00 00 00 00  |.....??.........|
000001c0  00 00 00 00 00 00 00 74  78 74 00 f5 eb 0e 05 08  |.......txt.??...|
000001d0  04 15 01 08 00 eb 02 62  c0 76 32 00 fe fe fe fe  |.....?.b?v2.????|
000001e0  fe fe fe fe fe fe fe fe  fe 55 55 55 55 55 55 55  |?????????UUUUUUU|
000001f0  55 57 77 55 55 55 55 55  55 55 55 55 55 55 55 55  |UWwUUUUUUUUUUUUU|
00000200  55 55 55 55 55 55 35 55  53 33 55 00 00 00 00 00  |UUUUUU5US3U.....|
00000210  00 50 00 00 00 07 77 77  77 77 77 77 77 77 77 00  |.P....wwwwwwwww.|

Turns out AutoDesk made a change to the SKD format and you can see the version number at 473rd byte (0x1D9). This version of SKD is required for later versions of AutoSketch to open and use the format. A special version of AutoSketch, 2.1fc, was released with limited features to allow users to open earlier versions of the SKD format and convert them to the second version of the format. The readme file for the 2.1fc version has this statement:

This limited release of AutoSketch has been provided for file conversion purposes only. All functionality other than opening and saving files has been removed from this release.

Please follow the steps below to perform a drawing file conversion for files created in AutoSketch Release 2.0 for Windows, or earlier. Once drawing files have been converted, you will be able to open them in AutoSketch Release 5.0 and later.

AutoDesk released the first version of AutoSketch for Windows in 1992. This first version for Windows used the new SKD format as well. Even though it was version 1.0 for Windows, the new version of the format is known as the v2.x format.

% hexdump -C AS1-S01.SKD
00000000  41 75 74 6f 53 6b 65 74  63 68 20 64 72 61 77 69  |AutoSketch drawi|
00000010  6e 67 20 64 61 74 61 62  61 73 65 0d 0a 1a 00 00  |ng database.....|
00000020  49 0b 00 00 00 00 00 01  00 00 00 00 00 00 00 00  |I...............|
00000030  00 00 00 00 00 40 41 00  00 10 41 00 00 00 00 00  |.....@A...A.....|
00000040  00 00 00 00 00 40 41 00  00 10 41 00 00 80 3f 01  |.....@A...A...?.|
00000050  00 07 00 00 00 00 00 00  00 00 00 00 00 00 00 33  |...............3|
00000060  33 33 33 33 33 d3 3f 00  00 00 00 00 00 f0 3f 00  |33333??......??.|
00000070  00 00 00 00 00 00 00 00  00 00 00 01 00 00 00 00  |................|
00000080  00 80 3f 00 00 80 3f 0a  00 08 00 00 00 00 00 ff  |..?...?........?|
00000090  ff 00 00 00 00 00 00 00  00 9a 99 99 99 99 99 1f  |?...............|
000000a0  40 cd cc cc cc cc cc 23  40 00 00 01 00 00 00 00  |@??????#@.......|
000000b0  00 00 00 00 00 f0 3f 00  00 00 00 00 00 f0 3f 00  |.....??......??.|
000000c0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
000001d0  00 00 00 00 00 00 00 e8  9a 76 32 00 00 00 00 00  |.......?.v2.....|
000001e0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|

This is the format used through version 2.1 for Windows which was released in 1996. It was after this version AutoDesk made a major change to the software. In version 5, skipping 3 and 4, an entirely new drawing engine was used, changing the software and the file format. This new format is actually the format used by the software the new drawing engine came from, DrafixCAD. AutoDesk purchased the software company Softdesk Drafix and used the DrafixCAD software, originally developed by Foresight Resources Corp., for this new version of AutoSketch.

Let’s compare a couple of DrafixCAD files to an AutoSketch 5 and 6 file.

% hexdump -C DEMOPLAN.CAD | head
00000000  0a 75 00 00 00 0b 02 38  30 13 05 46 4c 4f 41 54  |.u.....80..FLOAT|
00000010  14 05 53 48 4f 52 54 0c  04 30 2e 38 30 0d 08 4f  |..SHORT..0.80..O|
00000020  63 74 20 31 39 38 39 0e  12 44 72 61 66 69 78 20  |ct 1989..Drafix |
00000030  57 69 6e 64 6f 77 73 20  43 41 44 0f 06 49 42 4d  |Windows CAD..IBM|
00000040  20 50 43 10 07 44 4f 53  20 33 2e 30 11 06 4d 53  | PC..DOS 3.0..MS|
00000050  20 32 2e 31 12 1e 31 39  38 39 20 46 6f 72 65 73  | 2.1..1989 Fores|
00000060  69 67 68 74 20 52 65 73  6f 75 72 63 65 73 20 43  |ight Resources C|
00000070  6f 72 70 2e 00 28 43 03  00 00 29 b6 01 00 00 01  |orp..(C...)?....|
00000080  07 00 02 01 00 04 01 00  05 01 00 06 01 00 07 00  |................|
00000090  00 80 3f 08 00 00 09 0d  00 0a 01 00 0c 04 00 11  |..?.............|

% hexdump -C DEMOPLAN.CAD | head
00000000  0a 7d 00 00 00 0b 03 32  30 30 13 06 44 4f 55 42  |.}.....200..DOUB|
00000010  4c 45 14 05 53 48 4f 52  54 0c 03 32 2e 30 0d 0f  |LE..SHORT..2.0..|
00000020  4a 61 6e 75 61 72 79 20  37 2c 20 31 39 39 32 0e  |January 7, 1992.|
00000030  12 44 72 61 66 69 78 20  57 69 6e 64 6f 77 73 20  |.Drafix Windows |
00000040  43 41 44 0f 06 49 42 4d  20 50 43 10 07 44 4f 53  |CAD..IBM PC..DOS|
00000050  20 33 2e 30 11 06 4d 53  20 32 2e 31 12 1e 31 39  | 3.0..MS 2.1..19|
00000060  38 39 20 46 6f 72 65 73  69 67 68 74 20 52 65 73  |89 Foresight Res|
00000070  6f 75 72 63 65 73 20 43  6f 72 70 2e 00 28 28 04  |ources Corp..((.|
00000080  00 00 29 80 02 00 00 04  01 00 05 01 00 07 00 00  |..).............|
00000090  00 00 00 00 00 40 08 01  00 0a 01 00 0c 04 00 11  |.....@..........|

% hexdump -C ASv5-s01.SKF | head
00000000  0a 00 00 00 00 0b 03 34  30 31 01 00 00 00 38 00  |.......401....8.|
00000010  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|

% hexdump -C ASv6-s01.SKF | head
00000000  0a 00 00 00 00 0b 03 34  30 32 03 36 2e 30 01 20  |.......402.6.0. |
00000010  0f 4f 63 74 6f 62 65 72  20 32 2c 20 31 39 39 38  |.October 2, 1998|
00000020  01 00 00 00 38 00 00 00  00 00 00 00 00 00 00 00  |....8...........|
00000030  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|

You can see the similar pattern in the first 8 bytes. Just the 2nd and 7th byte being different. The 8th byte is consistent with all SKF files, and the 9th and 10th bytes turn out to be in sequence depending on the version.

Looking at the next few versions of AutoSketch we see: 

% hexdump -C AS7-s01.SKF | head
00000000  0a 00 00 00 00 0b 03 34  31 32 03 37 2e 30 08 42  |.......412.7.0.B|
00000010  75 69 6c 64 20 35 34 10  4f 63 74 6f 62 65 72 20  |uild 54.October |
00000020  31 35 2c 20 31 39 39 39  01 00 00 00 38 00 00 00  |15, 1999....8...|
00000030  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|

% hexdump -C AutoSketch8-s01.SKF | head
00000000  0a 00 00 00 00 0b 03 34  31 32 03 39 2e 30 08 42  |.......412.9.0.B|
00000010  75 69 6c 64 20 38 38 0a  30 37 2f 30 38 2f 32 30  |uild 88.07/08/20|
00000020  30 34 01 00 00 00 38 00  00 00 00 00 00 00 00 00  |04....8.........|
00000030  00 40 00 00 00 00 00 00  1f 40 00 00 00 00 00 00  |.@.......@......|
00000040  00 00 00 00 00 00 00 00  00 40 00 00 00 00 00 00  |.........@......|
00000050  20 40 00 00 00 00 00 00  00 00 00 00 00 00 00 00  | @..............|
00000060  00 00 02 00 00 00 76 5e  00 00 42 4d 76 5e 00 00  |......v^..BMv^..|
00000070  00 00 00 00 76 00 00 00  28 00 00 00 00 01 00 00  |....v...(.......|
00000080  bc 00 00 00 01 00 04 00  00 00 00 00 00 5e 00 00  |?............^..|
00000090  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|

% hexdump -C AutoSketch9-s01.SKF | head
00000000  0a 00 00 00 00 0b 03 34  31 33 03 39 2e 30 08 42  |.......413.9.0.B|
00000010  75 69 6c 64 20 38 38 0a  30 37 2f 30 38 2f 32 30  |uild 88.07/08/20|
00000020  30 34 01 00 00 00 38 00  00 00 00 00 00 00 00 00  |04....8.........|
00000030  00 40 00 00 00 00 00 00  1f 40 00 00 00 00 00 00  |.@.......@......|
00000040  00 00 00 00 00 00 00 00  00 40 00 00 00 00 00 00  |.........@......|
00000050  20 40 00 00 00 00 00 00  00 00 00 00 00 00 00 00  | @..............|
00000060  00 00 02 00 00 00 76 5e  00 00 42 4d 76 5e 00 00  |......v^..BMv^..|
00000070  00 00 00 00 76 00 00 00  28 00 00 00 00 01 00 00  |....v...(.......|
00000080  bc 00 00 00 01 00 04 00  00 00 00 00 00 5e 00 00  |?............^..|
00000090  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|

% hexdump -C AS10-s01.SKF | head
00000000  0a 00 00 00 00 0b 03 34  31 33 04 31 30 2e 30 08  |.......413.10.0.|
00000010  42 75 69 6c 64 20 31 31  0a 31 32 2f 30 32 2f 32  |Build 11.12/02/2|
00000020  30 30 38 01 00 00 00 38  00 00 00 00 00 00 00 00  |008....8........|
00000030  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000040  00 00 00 25 91 48 24 12  89 30 40 5d 2c 16 8b c5  |...%.H$..0@],..?|
00000050  62 27 40 00 00 00 00 00  00 00 00 00 00 00 00 86  |b'@.............|
00000060  01 36 00 02 00 00 00 76  5e 00 00 42 4d 76 5e 00  |.6.....v^..BMv^.|
00000070  00 00 00 00 00 76 00 00  00 28 00 00 00 00 01 00  |.....v...(......|
00000080  00 bc 00 00 00 01 00 04  00 00 00 00 00 00 5e 00  |.?............^.|
00000090  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|

Version 10 was the final version released of AutoSketch in 2008. It appears the SKF files from version 7 & 8 share the same format and 9 & 10 share one as well. This seems to be confirmed in the save as dialog in version 9 which lumps version 7 & 8 together.

So, if we wanted to make one signature for all SKF files, it might look something like:

0A000000000B0334(30|31)(31|32|33)

Or we can choose to split out versions if needed. For now, adding this signature to the existing PRONOM entry for SKF would be helpful. As for the earlier SKD format, we clearly need two signatures, one for the first version and one for the second.

Here is a small timeline of the different versions of AutoSketch.

AutoSketch Release 1.0 DOS 1986-10
AutoSketch Release 1.01 DOS 1987-02
AutoSketch Release 1.02 DOS 1987-09
AutoSketch Release 1.03 DOS 1988-02
AutoSketch Release 2.0 DOS 1989
AutoSketch Release 3.0 DOS 1990
AutoSketch Release 3.1 DOS 1991
AutoSketch Release 1.0 Windows 1992
AutoSketch Release 2.0 Windows 1994
AutoSketch Release 2.1 Windows 1996
AutoSketch Release 5 Windows 1997-11
AutoSketch Release 6 Windows 1998-10
AutoSketch Release 7 Windows 1999
AutoSketch Release 8 Windows 2001
AutoSketch Release 9 Windows 2004-09-20
AutoSketch Release 10 Windows 2008-11

I need to do a little more research on the DrafixCAD format, but I will update the signature when I do. As always take a look at my samples and suggested signatures on my GitHub page.