[Info-vax] Anyone interested in another public access system

[glen herrmannsfeldt]

P. Sture <paul.sture.nospam at hispeed.ch> wrote:
(snip, I wrote)
 
>> In the days of small memory, caching files in memory was
>> not possible.  The RT-11 file system allocates contiguously.
>> As I remember, the first file open is at the beginning of the largest
>> free area.  When another file is open, it is either at the
>> beginning of another large free area, or at the middle of the
>> free area being used by the previously opened file.  
 
> I can't remember whether it was a DIBOL specific thing, but on the RT-11 
> systems I worked with when opening a sequential file for output, the 
> allocation made was half of that free space, truncating at file close. 
> Therefore if more than one sequential output file was opened at the same 
> time, you _would_ get fragmentation. When an output file became full, 
> the system would ask you for a continuation file specification, then 
> continue.

I thought the first file was at the beginning, and the second
started half way.  I forget that it only gave half if there was
only one file.  I believe that subsequent files divide the
last one in half.  (1/2, 1/4, 1/8, ...).

> There was a trick in DIBOL to override this, by specifying to the open 
> statement the number of blocks to be allocated. IIRC this also worked 
> for the continuation file dialogue. Printer spool files were best aimed 
> at a disk with plenty of free space.  I believe Fortran also
allows that.

-- glen