Boston Post #1

[da]

My head's sort of spinning, but in an OK way.

Today, we spent the day with dpolicar and earthling132 earthling156 earthling177, walking on the beach (Revere), and lounging at their place and playing with Sasha (their pooch). Lots of fun conversation was had, and my brain was broken at least twice.

Bleh. If my screen were paper, there'd be a big hole right here where I would've erased and rewritten a half dozen thoughts, which are all getting jumbled in together. I think I should go lie down briefly before we go out to dinner. I promise I'll remember what I was going to say and write it up properly later.

Comments

[earthling177.livejournal.com]

I'll turn it around and ask where 177 came from? :)

Well, that is a geeky story actually. (I know, you are shocked...) ;-)

In school, most of the computers ran RSX-11M (PDP-11 machines) or VAX/VMS. DEC used to give a lot of the OSs to the same architect, and his file system had a convention that I still like, files have version numbers. So, you don't just have test.c, it's always something like test.c;1, test.c;2 etc. Every time you save the file, you create a new fresh file and a new version number. For most purposes, you never need to use the version number, the newest (by which the file system means highest version numbered) file gets used, so you just say things like "edit test.c" for example. There was at least one command ("purge test.c", for example) to get rid of the lower numbered versions and leave n versions untouched ("purge /keep=3 test.c"), and if you don't say anything, only the highest file number is left. The delete command can't just delete a file, you have to either tell it explicitly which one ("delete test.c;1") or all of them ("delete test.c;*"), so if you accidentally say "delete test.c" you get an error message. The thing I liked about those systems is that it was really easy to create data, and rather difficult to delete it by accident. The entire philosophy seemed to be that OS, apps etc were cheap, they come in a backup form that is installed and they can always be re-installed, but your data is the most precious thing stored and it should be preserved.

Well, the thing with that system is that every time you open a file for writing, it creates a new one unless you mention the file by its complete name (that is, with the file version). Which is fine for most purposes, except for apps that come from other systems and expect to find files (particularly files used as locks, but also files that have shared data) in some particular place, as opposed to using the OS's native mechanisms for passing messages and synchronization, like Mailboxes (a kind of bi-directional pipe), flags and shared memory.

So, at least in my circle of friends, we quickly started using ";177" as the file version in cases like that, like for example, "mailbox.flock;177", in case we needed unique file names -- that had several advantages, including that it doesn't conflict with a file name that normal users might be using (version numbers rarely reached that number). In RSX-11M the file version was an octal number that had to fit a (signed) byte, so "177" is the equivalent of the character "delete", and the highest bit pattern. In VMS the version number not only is decimal, but you have an entire integer-2 (16 bits), but we figured "tradition" has several interpretations, and ";177" was already set in people's minds anyway and we had never had a problem with file versions reaching that far anyway, so we left it that way. But now that group of people is very likely to just attach "177" to any name they want to make unique on the web when we can't have the original name.