Date: Tue, 26 Oct 2010 10:28:12 +0100 From: Roger Holmes <roger.holmes at microspot.co.uk> Subject: Re: What are these IBM 'thingys' Or 80 brushes, I think the holes in cards were made tall and narrow to make reading them that way easier. +++++++++++++++++++++++++++++++++++++++++++++ Exactly. In those electro-mechanical days cards were almost always read in parallel, i.e. long edge first, because that's how those machines worked; rotary selectors, type bars, sorter gates, etc., the timing of the entire system was based on and ran in sync with the card moving through the various digit positions 0 to 9 (and 11 & 12 for symbols and alpha). Want to add two numbers? Take a rotary 10-position switch and connect it mechanically through a solenoid-operated clutch so that as the card moves so does the switch, each position corresponding to a vertical location on the card. Starting with the switch in the 0 position, read the first card, engage the clutch when it passes the 0 position and drop the clutch when a brush makes contact through a hole in the card. Do the same with the second card and the rotary switch will read the sum (with a few extra solenoids and relays to handle carries). Want to print it? Simple: you have a type bar with the digits in reverse order, again synchronized to the rest of the machine. Start rotating the switch and moving the type bar together and when the switch hits 0 fire the type hammer. Want to sort your invoices by client number? Take the card deck over to your 08x sorter, those machines you've all seen in old movies where the cards move across and drop into different columns or pockets (usually flying out and across the room for amusement - it wasn't funny when it really did happen!). Rotate the column selector knob to the LSD column (it only had one moveable brush) and press Start. As the card moves, it passes a set of chutes each leading to one of those pockets and when the brush makes contact through the hole the card is diverted to whichever chute it's under at that exact moment. Go through all the cards, put the 10 piles back together in sequence, repeat for each column up to the MSD and presto, they're sorted. Ah, the good old days... I'd love to see some kind of emulation of these systems... When computers came along the whole paradigm shifted from parallel processing to serial, and those card readers did indeed read the card from left to right with only 12 brushes (more likely optical sensors) instead of top to bottom with 80, although IIRC there were some combined serial and parallel binary card formats. Of course now we've seen the error of our ways and have returned to parallel processing; a modern card reader would no doubt read cards top to bottom again, with each column connected to its own CPU. mike