More RT-11 questions - test-drb@ccmp.vtda.org

30 Apr 1999

...
 MY first guess (assuming the physical format is
identical, which isn't 
absolutely certain) is that there are extra words at the end of each 
directory entry. An RT11 directory entry consists of the filename, date, 
status and number of blocks that it corresponds to (note that the 
starting block is _not_ stored - you have to count the blocks used by all 
previous entries to figure that out). But it's possible at format-time to 
specify that each entry contains a number of extra words for the user to 
make use of. The PERQ interchange disk, while nominally an RT11 format, 
has 1 extra word in each directory entry that stores the number of bits 
used in the last block of the file, for example. 
...
 Maybe early versions of RT11 choke if given disks which
contain extra 
words in the directory entries... 
But V2C definitely has the support for extra directory entry words.  The
number of extra words for an entry is part of the directory header (at
the beginning of each directory segment).

...
 Most likely the result of someone PIPing to TT rather
than TT: 
Yep...

Remember, TT and TT: are different... the first is a file called
TT, the second is a device called TT...

The device block used for file operations is 4 words long, with
the first word being the device name (in rad50), the next two
words being the 6 character file name (in rad50), and the last
word is the file typ (extension, in rad50).

If you type TT, the CSI (the Command String Interpreter) will
build the following dblk (as it is called):

	.rad50	/DK/
	.rad50	/TT    /
	.rad50	/   /

whereas if you type TT:, the CSI creates the following dblk:

	.rad50	/TT /
	.rad50	/      /
	.rad50	/   /

					Megan Gentry
					Former RT-11 Developer

+--------------------------------+-------------------------------------+
| Megan Gentry, EMT/B, PP-ASEL   | Internet (work): gentry!zk3.dec.com |
| Unix Support Engineering Group |          (home):  mbg!world.std.com |
| Compaq Computer Corporation    | addresses need '@' in place of '!'  |
| 110 Spitbrook Rd. ZK03-2/T43   | URL:     http://world.std.com/~mbg/ | 
| Nashua, NH 03062               | "pdp-11 programmer - some assembler |
| (603) 884 1055                 |  required." - mbg                   |
+--------------------------------+-------------------------------------+