Re: ProDOS misc. questions

[david@wraith.cs.uow.edu.au (David E A Wilson)]

shack@deimos.frii.com (Randy Shackelford) writes:
>In article <31FDD36C.B59@cardshow.com>,
>Michael Guitton  <webmaster@cardshow.com> wrote:
>>o Why the root directory of a ProDOS volume is limited to 51 files?

>The main reason is that the EOF of the volume directory isn't stored on disk
>anywhere, it's just assumed to be $800, or four blocks. Varying the number
>of blocks can work, but not every app out there will support it. I experimented
>with making volumes with bigger volume directories using a block editor once,
>with fairly inconsistent results trying them with various apps.
>Trivia: the program disk on early Appleworks versions has less than a four
>block directory, with bit map relocated to match. I guess they did it to 
>squeeze some files on for which space was a little short on a normal disk.

The volume directory of /RAM (the 64K RAMdisk in aux memory in a 128K //e, //c
or //gs) has only one block. This broke early versions of BASIC.SYSTEM. The
current BASIC.SYSTEM and PRODOS files both support 1 and 4 block volume
directories (returning $200 and $800 lengths respectively). 1 block directories
are easy enough to check for - the forward link in the first block is $0000.
Any other size of volume directory would require scanning the whole thing.
-- 
David Wilson	Dept CompSci Uni Wollongong Australia	david@cs.uow.edu.au