Mechanical calculators (was: Re: *updating* 8088's)

-------------Original Message: Date: Fri, 30 Nov 2007 09:52:16 +0100 From: "Arno Kletzander" <Arno_1983 at gmx.de> Subject: Mechanical calculators (was: Re: *updating* 8088's) "Roy J. Tellason" <rtellason at verizon.net> wrote: Hmm, like, say, an old cash register? This design is called "Volltastaturmaschine" in German (would translate to "complete keyboard machine"). They have a latching mechanism that holds in one button per column of keys (0-9, representing one digit of a number). When a calculation is initiated, the protruding shaft of the latched key acts as a stop for a toothed rack or similar device which is used to advance the wheels of the accumulator register by as many teeth as the corresponding digit says. There are also designs which involve an arrangement of levers positioning an intermediate gear along the axis of a stepped drum, for example the Badenia VA-17/VARE-17. The big advantage is that zeros need not be entered (to enter 100.00, you just press the "1" button in the fifth column from the right) and that operators could learn to "touch-type" on these keyboards, effectively entering all digits of a number in parallel and greatly reducing cycle times. <snip> -- Arno Kletzander www.iser.uni-erlangen.de -----------Reply: The IBM unit record or Tabulating machines that we've been discussing had their roots in the same principles as these calculators, adding machines and cash registers, but instead of a depressed key stopping a moving rack in a certain position (a certain point of time in the machine's "cycle"), a set of wire brushes (later replaced by photocells) would make contact through the holes in the card as it moved vertically through the different digit positions, and pick a relay, latch a rotating selector (and lock a synchronized moving typebar if it was a printer) to represent that digit electrically. Like the manual full keyboards, all 80 digits/characters were processed simultaneously. Timing diagrams looked similar to the modern square waves we're all familiar with (although they were sometimes arranged in a set of concentric circles to represent a complete cycle), but instead of a continuous linear time line they had a definite beginning and end and were divided into equal-length "digit" times. When electronics started to replace more and more of the mechanical gears and relays there was a paradigm shift and everything switched to reading and processing cards "serially" ("parallel" from our modern perspective ;-), i.e. lengthwise by character, instead of all characters in "parallel" by digit. The "Accounting" or "Posting" machines _also_ known as EAMs (Electr(on)ic Accounting Machines) made by Burroughs, NCR etc. and used in almost every bank also used the same basic principle. Because a good operator could enter an entire multi-digit amount in one "keystroke" and data entry speed was more important than processing, they retained full keyboards for quite a while even after the gears and cams had been replaced with electronic equivalents. The moving racks and cams were simply replaced by a set of rotating 10-position selector "switches" and connected to the electronic "adjunct" with thick multi-conductor cables. The processors in turn operated on "words" consisting of 15 or more 10-"bit" "bytes;" guess you could call it parallel processing... m