Date: Sun, 9 Jun 1996 21:25:11 GMT From: James Raynard <fqueries@jraynard.demon.co.uk> To: jmb@freefall.freebsd.org Cc: jbarrm@panix.com, questions@freebsd.org Subject: Re: Design & Implementation of 4.4BSD Message-ID: <199606092125.VAA04908@jraynard.demon.co.uk> In-Reply-To: <199606091250.FAA03535@freefall.freebsd.org> (jmb@freefall.freebsd.org)
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>>>>> "Jonathan M. Bresler" <jmb@freefall.freebsd.org> writes:
>
> Barry Masterson wrote:
> >
> > Hi,
> >
> > I'm working my way thru the recently released book entitled
> > "The Design and Implementation of the 4.4BSD Operating System",
> > and have come across some algorithm code samples on pages 199 & 203:
> >
> > disksort(dq, bp)
> > drive queue *dq;
> > buffer *bp;
> > {
> > if (drive queue is empty) {
> > place the buffer at the front of the drive queue;
> > return;
> > }
> > if (request lies before the first active request) {
> > locate the beginning of the second request list;
> > sort bp into the second request list;
> > } else
> > sort bp into the current request list;
> > }
> >
> > I'm familiar with the basics of c/c++, perl, shell scripts, but this
> > use of "the", "of", "into", "at" is something I've yet to see. It
> > seems a little too human readable to be real code.
> >
> > What language is this? Are there other examples of this type of
> > programming in the FreeBSD source code?
>
> its called "psuedo-code". rather then present the actual source
> the authors are presenting the algorithm stripped of the details
> of data structures and pointer (etc....) that obscure the purpose
> of the code. rather liek the difference between the blueprints
> and the building itself.
It might also be worth mentioning that pseudo-code is very useful when
writing code - first decide what the function is supposed to do, then
write down pseudo-code that describes this in more detail, then write
comments based on the pseudo-code. All you have to do then is fill in
the gaps between the comments! 8-)
> ps. this is one of the joys of FreeBSD--getting to see the real
> code
Absolutely!
--
James Raynard, Edinburgh, Scotland | http://www.freebsd.org/~jraynard/
james@jraynard.demon.co.uk | jraynard@freebsd.org
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