Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!zaphod.mps.ohio-state.edu!sdd.hp.com!decwrl!ucbvax!bloom-beacon!primerd!ENI!!EAF
From: EAF@.Prime.COM
Newsgroups: comp.lang.misc
Subject: Re: Query
Message-ID: <126800008@.Prime.COM>
Date: 16 Aug 90 08:29:00 GMT
References: <5754@uwm.edu>
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Nf-ID: #R:uwm.edu:-575400::126800008:000:916
Nf-From: .Prime.COM!EAF    Aug 16 08:29:00 1990


I should have been more careful in separating different OS aspects.

Typically a good I/O system will do some buffering for you.  Most competent
operating systems maintain a cache of disk blocks in memory for you.  In
addition if you employ language oriented I/O, a buffer will be maintained
for you in the I/O library's storage pool.  When you read a sentence into
your buffer, it can come from the Language Library buffer.  If your
language I/O library is intelligent and you are reading sequential
data, the language library will call on the OS to read the next disk
block into memory, often before it is required.  When the new block is
needed it will be brought from the cache into the language library buffer
and then into your sentence space.

While this is not double buffering in the sense that a single entity is
aware of it and planning for it, it is double buffering and it does improve
I/O concurrency.