Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!zaphod.mps.ohio-state.edu!julius.cs.uiuc.edu!apple!amdahl!karl
From: karl@uts.amdahl.com (Karl Rowley)
Newsgroups: comp.lang.fortran
Subject: Re: File handling in Fortran 77
Message-ID: <58CS02Sscfr.01@amdahl.uts.amdahl.com>
Date: 5 Oct 90 00:03:02 GMT
References: <46016@masscomp.ccur.com> <1990Sep12.215551.16135@agate.berkeley.edu> <1990Oct1.174040.16208@ux1.cso.uiuc.edu> <2153@key.COM> <28454@pasteur.Berkeley.EDU>
Reply-To: karl@amdahl.uts.amdahl.com (Karl Rowley)
Organization: Amdahl Corporation, Sunnyvale CA
Lines: 32

In article <28454@pasteur.Berkeley.EDU> ndeng@euler.Berkeley.EDU.UUCP () writes:
>In article <2144@key.COM> sjc@key.COM (Steve Correll) writes:
>
> >Fortran 90 permits you to specify POSITION='REWIND', POSITION='APPEND', or
> >POSITION='ASIS' in the OPEN statement. The latter leaves the file position
> >unchanged if the file exists and was already connected.
>                                       ^^^^^^^ ^^^^^^^^^
>Correct me if I am wrong. But how could one CONNECT to a file before OPEN it?
> 

Look at COS (the Cray Operating System) as an example.  A dataset has a 
position (like a tape on a tape drive) that it retains between the execution
of various programs.  The "REWIND" statement can be used in the job control
language to rewind a dataset outside of a program.  Datasets are "connected",
positioned, and even assigned to particular Fortran unit numbers before 
an application is run.

The same basic model holds true for VSOS on the Cyber 205 (and I suspect
for some other systems too).  Cray and Cyber experts please forgive me
if I have messed up any details here.

Does the Fortran standard say what the default position of a file is when
it is OPENed?  I think this is vendor-dependent.

There are other models for handling files that differ from what Unix
provides -- Fortran attempts to accomodate them.

				Karl Rowley
				Amdahl Corp.
				Santa Clara, California
				karl@uts.amdahl.com
				...!ames!amdahl!karl