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From: Kragen Javier Sitaker <kragen@canonical.org>
Newsgroups: alt.folklore.computers
Subject: Re: Tops-10 filename/extension representation [was Re: Origin Of Filename Extension Dot Separator]
Date: Sat, 05 Sep 2026 10:14:01 -0300
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Rich Alderson <news@alderson.users.panix.com> writes:
> Johann 'Myrkraverk' Oskarsson <johann@myrkraverk.invalid> writes:
>> Yes, we have to wonder what's in a name.  If I remember correctly, the
>> FAT [1] file system has separate entries for the /filename part/ and the
>> /extension part/.  
>
> On disk, user file directories are made up of pairs of 36 bit words.
> The first word contains the SIXBIT (ASCII values reduced by 40(8))
> name, up to 6 characters, and the second word contains the SIXBIT
> extension in the left halfword and a pointer to the first block of the
> file in the right halfword.

I have this vague memory suggesting that RT-11 and RSX-11 suffered from
the same 6.3 FILNAM.EXT limitation, though using RADIX-50 instead of
SIXBIT.  Was CP/M the system responsible for extending that to 8.3?

I don’t think anybody ever shipped a filesystem that tried to use
Baudot-Murray code for filenames...

Kragen