The Universe of Disco

My Favorite NP-Complete Problem at !!Con 2016

Back in 2006 when this blog was new I observed that the problem of planning Elmo’s World video releases was NP-complete.

This spring I turned the post into a talk, which I gave at !!Con 2016 last week.

Talk materials are online.

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Typewriters

It will suprise nobody to learn that when I was a child, computers were almost unknown, but it may be more surprising that typewriters were unusual.

Probably the first typewriter I was familiar with was my grandmother’s IBM “Executive” model C. At first I was not allowed to touch this fascinating device, because it was very fancy and expensive and my grandmother used it for her work as an editor of medical journals.

The “Executive” was very advanced: it had proportional spacing. It had two space bars, for different widths of spaces. Characters varied between two and five ticks wide, and my grandmother had typed up a little chart giving the width of each character in ticks, which she pasted to the top panel of the typewriter. The font was sans-serif, and I remember being a little puzzled when I first noticed that the lowercase j had no hook: it looked just like the lowercase i, except longer.

The little chart was important, I later learned, when I became old enough to use the typewriter and was taught its mysteries. Press only one key at a time, or the type bars will collide. Don't use the (extremely satisfying) auto-repeat feature on the hyphen or underscore, or the platen might be damaged. Don't touch any of the special controls; Grandma has them adjusted the way she wants. (As a concession, I was allowed to use the “expand” switch, which could be easily switched off again.)

The little chart was part of the procedure for correcting errors. You would backspace over the character you wanted to erase—each press of the backspace key would move the carriage back by one tick, and the chart told you how many times to press—and then place a slip of correction paper between the ribbon and the paper, and retype the character you wanted to erase. The dark ribbon impression would go onto the front of the correction slip, which was always covered with a pleasing jumble of random letters, and the correction slip impression, in white, would exactly overprint the letter you wanted to erase. Except sometimes it didn't quite: the ribbon ink would have spread a bit, and the corrected version would be a ghostly white letter with a hair-thin black outline. Or if you were a small child, as I was, you would sometimes put the correction slip in backwards, and the white ink would be transferred uselessly to the back of the ribbon instead of to the paper. Or you would select a partly-used portion of the slip and the missing bit of white ink would leave a fragment of the corrected letter on the page, like the broken-off leg of a dead bug.

Later I was introduced to the use of Liquid Paper (don't brush on a big glob, dot it on a bit at a time with the tip of the brush) and carbon paper, another thing you had to be careful not to put in backward, although if you did you got a wonderful result: the typewriter printed mirror images.

From typing alphabets, random letters, my name, and of course qwertyuiops I soon moved on to little poems, stories, and other miscellanea, and when my family saw that I was using the typewriter for writing, they presented me with one of my own, a Royal manual (model HHE maybe?) with a two-color ribbon, and I was at last free to explore the mysteries of the TAB SET and TAB CLEAR buttons. The front panel had a control for a three-color ribbon, which forever remained an unattainable mystery. Later I graduated to a Smith-Corona electric, on which I wrote my high school term papers. The personal computer arrived while I was in high school, but available printers were either expensive or looked like crap.

When I was in first grade our classroom had acquired a cheap manual typewriter, which as I have said, was an unusual novelty, and I used it whenever I could. I remember my teacher, Ms. Juanita Adams, complaining that I spent too much time on the typewriter. “You should work more on your handwriting, Jason. You might need to write something while you’re out on the street, and you won't just be able to pull a typewriter out of your pocket.”

She was wrong.

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