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From: Martin Gregorie on 17 Apr 2010 07:20
On Fri, 16 Apr 2010 20:06:37 -0400, Arne Vajhøj wrote:

> It is: sequential, relative and indexed.
>
> Random access (as opposed to sequential access) is possible to all file
> organizations.
>
> Indexed is really a little database in itself.
>
> I believe that some IBM OS'es have similar functionality.
>
I think all mainframes from that period had more or less the same
capabilities for accessing records in a disk file. I used ICL kit (first
1900 series and then 2900 series). These offered the following access
methods:

sequential - variable length records, prefixed with a length word
stored in arrival sequence.
self-indexed - fixed length records, retrieved by record number
indexed - fixed length records, retrieved by a key field, stored
in key sequence and accessed via a distributed index
random - fixed length records, retrieved by a key field,
stored via a hash of the key

All four organisations could be read sequentially.

In that era files tended to occupy fixed places on a disk: the 1900's
basic file allocation amounted to partitioning the disk and treating each
partition, which was named for access, as a file. Source and executables
were kept in 'subfiles' - variable sized chunks of a file. Only the
George 3 OS had the sort of hierarchic filing system that we now expect.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |
From: Eric Sosman on 17 Apr 2010 07:57
On 4/16/2010 8:06 PM, Arne Vajh�j wrote:
> On 16-04-2010 09:07, Eric Sosman wrote:
>>
>> Long ago when I worked with VMS, it supported three "file
>> organizations:" Sequential, Random, and Indexed.
>
> No - it is: sequential, relative and indexed.

Thanks for the correction. (As I said, my VMS work was
long ago, and my gray cells suffer a few parity errors.)

--
Eric Sosman
esosman(a)ieee-dot-org.invalid
From: Mike Schilling on 17 Apr 2010 10:41
Eric Sosman wrote:
> On 4/16/2010 8:06 PM, Arne Vajh�j wrote:
>> On 16-04-2010 09:07, Eric Sosman wrote:
>>>
>>> Long ago when I worked with VMS, it supported three "file
>>> organizations:" Sequential, Random, and Indexed.
>>
>> No - it is: sequential, relative and indexed.
>
> Thanks for the correction. (As I said, my VMS work was
> long ago, and my gray cells suffer a few parity errors.)

A VAX would have corrected those, or at least detected them.


From: Stanimir Stamenkov on 17 Apr 2010 11:16
Thu, 15 Apr 2010 21:28:43 +0000 (UTC), /Martin Gregorie/:

> only the Unices support symbolic links or multiple hard links per file.

Windows with NTFS supports file hard links and directory symbolic
links since Windows 2000:

http://msdn.microsoft.com/en-us/library/aa363860(VS.85).aspx
http://www.microsoft.com/resources/documentation/windows/xp/all/proddocs/en-us/fsutil_hardlink.mspx
http://technet.microsoft.com/en-us/sysinternals/bb896768.aspx

AFAIK Windows 7 supports file symbolic links, also.

--
Stanimir
From: Arne Vajhøj on 18 Apr 2010 21:52
On 17-04-2010 07:20, Martin Gregorie wrote:
> On Fri, 16 Apr 2010 20:06:37 -0400, Arne Vajhøj wrote:
>> It is: sequential, relative and indexed.
>>
>> Random access (as opposed to sequential access) is possible to all file
>> organizations.
>>
>> Indexed is really a little database in itself.
>>
>> I believe that some IBM OS'es have similar functionality.
>>
> I think all mainframes from that period had more or less the same
> capabilities for accessing records in a disk file. I used ICL kit (first
> 1900 series and then 2900 series). These offered the following access
> methods:
>
> sequential - variable length records, prefixed with a length word
> stored in arrival sequence.
> self-indexed - fixed length records, retrieved by record number
> indexed - fixed length records, retrieved by a key field, stored
> in key sequence and accessed via a distributed index
> random - fixed length records, retrieved by a key field,
> stored via a hash of the key
>
> All four organisations could be read sequentially.

And there were often pretty good language support for
those accesc methods in Cobol, Fortran, Pascal etc..

Arne
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