(j3.2006) Retro cool to go with your Fortran compiler

Lawrie Schonfelder j.l.schonfelder
Wed Dec 15 14:37:18 EST 2010

The skill of using a slide rule was in mechanically "sliding it" accurately and fast and
interpolating with precision. Mine has a vernia which allows the 3rd place to be done more correctly
than by eye.
There was also a skill in using a Bruns Viga but I preferred the Marchant, it had an electric motor
that rotated the wheels rather than depending on human "motivation".
Hartree, the great calculator of atomic physics, used hand calculators to solve the first
self-consistent field equations of atomic physics using first his own effort, then his sister (I
think) and eventually an army of calculators.
Some of the early numerical programs used many of his short circuiting methods. Solving
integro-differential equations with 1024 words needed some clever shortcuts.

Lawrie Schonfelder
Wirral, UK

> -----Original Message-----
> From: j3-bounces at j3-fortran.org [mailto:j3-bounces at j3-fortran.org]On
> Behalf Of Van Snyder
> Sent: 15 December 2010 19:09
> To: fortran standards email list for J3
> Subject: Re: (j3.2006) Retro cool to go with your Fortran compiler
> On Wed, 2010-12-15 at 04:58 -0800, Jerry Wagener wrote:
> > alas, one can compute with it to only about two significant figures
> > (in some cases you can interpolate close to three significant figures)
> > - guess that was good enough for much early engineering work.
> There was an observatory in Germany that had a 20-meter slide rule with
> a magnifying cursor.  It was reputedly good for six digits.
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