[TUHS] Re: Compatibility question

On 12/19/23, Clem Cole <clemc(a)ccc.com> wrote: For the edification of those who don't know, the 1403 line printer and its brothers worked like this. There was a (removable and switchable) horizontal cartridge that sat midway in the printer, laid out horizontally across the paper, behind an ink-soaked cloth band located between the print train and the paper. Behind the paper was a series of 132 hammers (one per column of print). The cartridge contained a single chain of type that was spun at high speed. Whenever the position of a desired character passed in front of its desired colu, that column's hammer struck the back of the paper and thus printed the character. There were several print trains available, just as there were several typeballs for the IBM Selectric typewriter. One of these used a space character ' ' both for the space and for the underscore '_'. This was the origin of using underscores to represent spaces in program identifiers. The other way to do line printing is to have a rotating drum with the full character set for each column. This is the way the DEC line printers worked. Of course there were minor inaccuracies in the timing of the hammers, and with the drum-based printers this resulted in wavy lines. There were inaccuracies in the print train-style printers, too, but waviness in the columns is not as noticeable to the eye as waviness in the lines. Coming from the IBM world, I considered the DEC printers total junk. Yes, the 1403 was very loud. The pitch of the noise varied with the sequence of characters being printed. Some IBM hacker (yes, they existed) came up with a deck of cards that, when printed, played "Anchors Aweigh" on the 1403. IBM field service wasn't very keen on this hack because it put a lot of wear-and-tear on the print train. -Paul W.