[ale] Engineering Archaeology

Sun Jan 18 18:51:02 EST 2026

Years ago there was a very famous case of a computer programmer that
"misdirected" a lot of money by truncating fractions of a cent, instead of
rounding, and storing those fractions of a cent into their own account.
This has come to be known as "salami slicing" and is a lot harder to do
with modern accounting systems.

md

On Sun, Jan 18, 2026 at 11:51 AM Jeff Lightner via Ale <ale at ale.org> wrote:

> I owned a slide rule in high school but electronic calculators were around
> by the time I was a senior so I was never terribly proficient with it.
>
> The well to do kids were buying the high end TI calculators but I could
> only afford a model with basic functionality.   It weighed a lot and the
> battery didn't last long.   That was back in the days they would blank the
> display after a few seconds of inactivity, trying to preserve battery.
>
> It was just as well though.   In my math and science classes we weren't
> allowed to use devices when doing calculations on tests so it forced me to
> do things by hand.
>
> Later in my hospitality/accounting career they initially didn't have
> electronic or computerized systems early on.   Many of the financial books
> and reporting I did were done by hand.  As time went by electronic systems
> appeared and quickly evolved to computerized systems.    I always had to
> laugh when the computer went down as co-workers would say we couldn't check
> people in or out.   I explained that hotels actually existed long before
> such systems so it was in fact possible.
>
> -----Original Message-----
> From: Ale <ale-bounces at ale.org> On Behalf Of jon.maddog.hall--- via Ale
> Sent: Sunday, January 11, 2026 1:44 PM
> To: Atlanta Linux Enthusiasts <ale at ale.org>
> Cc: jon.maddog.hall at gmail.com <jonhall80 at comcast.net>
> Subject: Re: [ale] Engineering Archaeology
>
>
>
> "If we applied such logic to when we were starting out - "slide rules work
> just fine, don't need no electricity, storage, keyboards, monitors, etc."
>
> Slide rules are an interesting example. Stop and think about the
> incredible application of logarithms being painted on two sticks, then
> slide those sticks back and forth to be able to multiply two numbers via
> adding two logarithms of them.
>
> Genius.
>
> And a fine example of analog mathematics being able to solve engineering
> issues.
>
> Usually only used to calculate to three levels of precision, they were
> "good enough" to do the calculations in an age where three levels of
> precision was about all we could do in any type of manufacturing....so why
> calculate to any greater precision, whether you are manufacturing a door
> knob or a bridge?
>
> Fast forward to floating point arithmetic in a computer.   How many of us
> have fallen into the trap of trying to "equate" two floating point numbers,
> only to realize that "two" really has a value of
> "1.999999..something-mumble"
>
> When I was teaching at Hartford State Technical College in 1975 the school
> store was cleaning out their inventory and found about ten beautiful
> "Aristo-Multilog Slide Rules", still in their box, complete with leather
> carrying case and instructions.
>
> The store was selling them for five dollars each, down from their original
> price that was probably close to 100 dollars.   I bought all ten, then gave
> them out as prizes to good students, showing them how to use them and
> explaining the significance in computer science.  I have two left.
>
> I did not expect the students to become as expert at using the slide rule
> as I was, but I was happy to see that they understood the significance of
> the lesson
>
> md
>
> > On 01/10/2026 8:36 PM EST Ron via Ale <ale at ale.org> wrote:
> >
> >
> > Jeff Lightner via Ale wrote on 2026-01-10 14:50:
> >
> > > In my later years when I would speak to people about “the old days”
> > > and things such as RS232-C and/or Hayes modem commands I realized
> > > that while it was likely true I’d forget much of the detail it
> > > didn’t mean younger folks would never know more than I’d forgotten.
> > > They would instead have no need for what I’d forgotten (for the most
> > > part) and eventually would learn things I’d never learn.
> >
> > Insightful comment.
> >
> > Of course, usual disclaimers of "not everyone, not always, not
> > everything" apply:
> >
> > The "kids today" are learning lots of great new things and pushing
> > boundaries in new directions. They're exploring new ways to do stuff
> > and aren't sold on "we've always done it this way, so we should
> > continue to do it this way".
> >
> >
> > Too often I see that attitude by other, fellow tech old-timers.
> >
> >
> > If we applied such logic to when we were starting out - "slide rules
> > work just fine, don't need no electricity, storage, keyboards,
> > monitors, etc." - I'm sure most of us would've found it unconvincing.
> >
> >
> > Let them have their chance, some ideas will work, some won't, and it's
> > their world now.
> >
> >
> > Anyway, appreciate the thought provoking post.
> >
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