### Analog Calculators For Boffins And Astronauts

##### By James Grahame

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*Duncan Waldron writes... *Long ago, in the mists of time, way before the ultra-modern IBM PC revolutionised serious number-crunching, and even before the pocket calculator freed the masses from the drudgery of hard sums, no serious student or boffin would be seen without his/her trusty slide rule.

A marvellous gadget, sleek and silent, and best of all - battery free, the slide rule was how you worked things out. Unless of course, you only had log tables. Well, there were mechanical and electronic adding machines, but you couldn't easily slip one into your back pocket or satchel.

The slide rule was one of those timeless, essential tools which, in the hands of an expert, could work wonders. To the rest of us, who encountered them only in school, there tended to be a lot of mystery surrounding some of the scales and markings. Frustratingly, you couldn't add or subtract, but multiply, divide, raise to powers, derive logarithms, and so on into ever deeper recesses of mathematical speciality - you could certainly do all of that.

Once upon a time, electronic calculators were not allowed in schools, or at least - not into exam rooms. We were then forced to buy a slide rule when heavy calculating was required. Before too long though, the authorities had relaxed their attitude (but only after yours truly had procured a good old British Thornton 'rule), and transistor-assisted calculation was available to every school student - at least, once the price had dropped sufficiently. Thereafter, the slide rule was pretty much consigned to the same historical bin as the abacus.

Slide rules can still be had, and will still work every bit as well as they did 30 years ago. I know at least one programmer who likes to use a slide rule at times, just because of the ease of obtaining an approximate answer, when 10 decimal places of accuracy are not required. *[Check out our writeup on Curt Herzstark's brilliant Curta for a different 'twist' on mechanical calculators.]*