Sunday brain tickler

[Jules Richardson]

On 01/09/2017 11:51 AM, Chuck Guzis wrote:
> On 01/09/2017 09:28 AM, Fred Cisin wrote:
>> Need there BE a filename?
>>
>> An OS, particularly for a word processor, could have an IMPLICIT list
>> of filenames on a disk of DOCUMENT1 DOCUMENT2 DOCUMENT3
>
>
> I found this document:
>
> http://www.dtic.mil/get-tr-doc/pdf?Location=U2&doc=GetTRDoc.pdf&AD=ADA199551
>
> about transferring Lanier "No Problem" files to a Unix (Gould 9050)
> mini.  The interchange program was a serial-comms program, so no value
> to disk interpretation.

I suppose *if* you had a disk with the program on then it would give a 
known name to be searching for... except that the doc seems to call it 
TTY_ASCII in places and ASCII-TTY in others :-(

> But apparently files were named--and some sort of name compression
> appears to be in use as the name of the comms program is 9 characters
> long, while the file name area appears to be only 8 bytes in length.

It seems unlikely that a simple system would resort to something like 
frequency analysis of characters when encoding filenames, though, 
particularly given the size of the data (the overhead would probably not 
make it worthwhile) - so I'm guessing we should be looking at "plain text", 
just with some unusual character size or distribution.

I did hack some quick code to alter the character size (6, 7 and 8 bits), 
spacing between characters (0, 1 and 2 bits) and offset from the start of 
the stream, then 'slide' the resulting data through the ASCII table and 
search for the "LTER" name that you mentioned previously, but without any 
luck. That does make the assumption that values for A-Z are contiguous, 
which seems likely but not certain.

I didn't look at 5 bit characters, which is a possibility if only alpha 
characters and not numerics are allowed in filenames.

I'm not sure if filenames are stored in their entirety, though - I think 
there was an example in that PDF which seemed to imply that pages have 
their own short names, and that these might be concatenated to form an 
overall name for the group of pages - I need to do more than just skim-read 
the document to understand that. It makes me wonder if there isn't some 
very short (2 or 3 character) limit on individual directory entries though, 
and these are chained together to make a larger name (and file)?

cheers

Jules