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From: ok@goanna.cs.rmit.oz.au (Richard A. O'Keefe)
Newsgroups: comp.lang.misc
Subject: Re: Query
Message-ID: <3572@goanna.cs.rmit.oz.au>
Date: 16 Aug 90 06:10:49 GMT
References: <5754@uwm.edu> <126800007@.Prime.COM>
Organization: Comp Sci, RMIT, Melbourne, Australia
Lines: 32

In article <126800007@.Prime.COM>, EAF@.Prime.COM writes:
> It depends on the way in which your computer buffers data.  Many computers
> double buffer data.  That is they read it in as disk blocks and keep it
> in main memory.

That is *NOT* double buffering.  That's buffering, pure and simple.
Multiple buffering is when you have N buffers in memory (N > 1) and
the operating system reads ahead, so that by the time you finish working
on one buffer-full the next buffer-full has already been read for you
without waiting, or writes behind, so that it is still writing out one
buffer while you are filling the next (anyone remember LOCATE mode?).

It's not a function of computers, either.  It's a function of (operating
systems) and (programing language runtime support libraries).  The "stdio"
package under UNIX typically does single buffering (a struct _iob contains
one pointer to a buffer) with synchronous reads, however some versions of
UNIX will do read-ahead and/or write-behind so that you get _some_ of the
benefit of double buffering.

The bottom line for the original poster is

	Use the high-level I/O operations provided in your programming
	language: READ and WRITE statements in Fortran, READ, READLN,
	WRITE, WRITELN, GET, PUT in Pascal, any <stdio.h> function or
	macro in C, and

		Don't Panic!

	it's Someone Else's Problem (the programming language vendor's).

-- 
The taxonomy of Pleistocene equids is in a state of confusion.