Path: utzoo!attcan!uunet!husc6!bloom-beacon!tut.cis.ohio-state.edu!mailrus!ames!pasteur!ucbvax!VAX1.CC.LEHIGH.EDU!LUSGR
From: LUSGR@VAX1.CC.LEHIGH.EDU (STEVE ROSEMAN)
Newsgroups: comp.os.vms
Subject: Re: How Fortran BACKSPACE Works
Message-ID: <8805242011.AA16127@ucbvax.Berkeley.EDU>
Date: 23 May 88 16:11:00 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 20

> From: gr47 <sdcc6!sdcc12!gr47@ucsd.EDU>
> Subject: Curious as to how Fortran BACKSPACE works

> I am curious as to how Fortran BACKSPACE works.  I vaguely remember
> reading in one of the orange manuals that BACKSPACE simply causes
> the logical unit to be rewound and read from THE BEGINNING forward to
> the record immediately preceding the current one.  Is this true?
> How are huge time delays avoided when BACKSPACE'ing large files, or
> are delays not avoided?  Or do I remember wrong, and does BACKSPACE
> use the saved (?) position of the start of the previous record to do
> its task?

It appears the above is true.  I did some timing tests a few months ago,
and it takes a rather long time to go back 1 record in a large file.


Steve Roseman
Lehigh University Computing Center
LUSGR@VAX1.CC.LEHIGH.EDU or
LUSGR@LEHICDC1.BITNET