Subject: Re: RL01 support in NetBSD?
To: Dave McGuire , Johnny Billquist <bqt@Update.UU.SE>
From: Megan <>
List: port-vax
Date: 02/19/2000 11:32:25
>. All files must be contigous.


>. You can only have one file open for writing on the disk at the same
>  time.

Not at all true...  When you create a file for the first time, you specify
the size you need.  This can be
	1) A specific size
	2) The largest continguous space
	3) 1/2 the largest, or the second largest (whichever is larger)

If you attempt to write beyond the end of the space allocated, you get
an EOF indication.  Most of the utilities have the capability of having
multiple files open for writing at one time -- how else would you expect
MACRO to produce an OBJ file and a LST file at the same time, and for
LINK to produce a SAV, MAP and symbol table file.

When you close the file, it closes to the highest block number actually
written.  If you want to *extend* a file, you have to go through some
real gyrations.

>. The directory is a few blocks at the beginning of the disk.

True.  Directory begins in block 6 of the disk, and extends to no more
than block 67.  Directory segments (which contain directory entries)
are two blocks long each.  So the first segment is blocks 6/7.  You
can have up to 31 segments.  Other than the primary directory segment,
blocks 6/7, other directory segments can be used in any order, and so
they are a linked list.  Each used segment points to the next one in
the list.  Last has a null pointer.

>. The maximum file size is 65535 blocks.

Yes and no... The maximum file size is contained in a 16-bit word, but
since the maximum *volume* RT supports is 16-bits, and out of this
comes the boot block, home block and directory blocks, the absolutely
maximum sized file you could have (and only one file could be on the
volume) is approx 65467 blocks.

					Megan Gentry
					Former RT-11 Developer

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