13. Oktober 2017

Listening to Compter Bugs

We’ve lost the ability to listen to information – by ear, by hearing. Helga Rietz describes that in her article «Die Temperatur nach Noten» (“The temperature by musical notes”) in my preferred newspaper, the Neue Zürcher Zeitung, on October 6, 2017. She writes about the sonification of data, of “science music”, and gives numerous examples with astronomy, with science, and other patterns that were discovered just by listening. Find the (German) article online here and the paper copy at http://bit.ly/2ylIwqP = https://zeitungsarchiv.nzz.ch/neue-zuercher-zeitung-vom-13-10-2017-seite-9.html?hint=19743452

An ICL 1903 around 1965 – still without disc (often spelled disk at that time) in Holbeck, England 
 I have my own experience with hearing technology at work.
   In the year 1969 in West Berlin my friend Ulrich Bosler and I were allowed to use Technical University’s mainframe during nights for our engineer diploma program. The largest computer in Berlin then, a ICL 1904 that had just gotten the newest gadget, disc drives, the size of American washing machines. Magnetic tapes were standard to store programs and data. We kept our program, an Exapt compiler written in in Fortran II for portability, on some 7,000 punch cards, so as to be able to quickly correct the program. To write our thesis we used another computer, less in demand, in another building, a Digital Equipment PDP 10 as line editor. At that time texts usually were written “offline” on purely mechanic typewriters.
   The ICL 1904 had a disc operating system (to be started by loading a sizeable punched tape), and was able to run four programs at the same time (“multiprogramming”). The disc was used for swapping, if necessary (called overlaying by Wikipedia). As we typically were all alone on the machine, there was only one program running (if at all …), ours.
Paper Tape Rewinder,
the later cordless model
originally for $ 150.
HP Computer Museum
   The operating system was controlled by an American electromechanic teletypewriter or teleprinter. As there were no “displays” like today, these 7 bit ASCII typing machines from the standard “four row” 110 baud telex service by Western Union (TWX) (110 characters per second), were the normal “keyboards” for all computers at that time, except for some European models using local 5-channel telex machines (see Baudot code) and Control Data, using six bit bytes rather than eight bit bytes. Incidentally a US teletype needed a sizeable 220-110 Volt stepdown transformer. But it could be used for the usual paper tape winder as well, derived from standard electric American erasers, mostly from these. (In Europe we still manually used a piece of india rubber to erase.)    
Teletypewriter to control computers.
Price advertized $ 1450. More here.
We used those with an adjustable mono
loudspeaker in the front cover.
Other example here.
So we had a loudspeaker in the console typewriter, with a little knob to turn volume up or down. Like a radio receiving electromagnetic interference by spark plugs, this litte “radio” reproduced the switching operations of the computer’s CPU, central processing unit.
   You could hear the computer at work.
   What you heared was reassuring – most of the time. You could hear loops, notice interrupts (peripheral devices bringing in some fresh data), and when an error stopped the program the sound stopped as well, at least its melody.
   The computer sound indicated program errors as well: You could hear a program looping indefinitely, when it repeated a sequence over and over and over again without change. Normally you are afraid to manually stop a program, to forcibly “end a task” as you’d say today. It might still be productive, progressing, just slow. With the ICL’s loudspeaker we could hear progress – or kill the program, dump a bit of memory, and find out in what loop it had hung. Even then, finding the place in the source program where we had stopped the program, was difficult.

Today the operating system of an ICL 1900 can be run on a Raspberry PI, more here.

Memories and specifications of the ICL 1900 by Brian Spoor. Very readable!
How I tried to trick the ICL 1904
• Another old story: The HP 3000 in Geneva 1972
• Another old story: A modem message via tape recorder

More stories: https://blogabissl.blogspot.com/2017/10/old-computer-stories-hp-2116-et-al.html

More on early Teletype code: www.colossus-computer.com/colossus1.html#appendix1

Link to here: https://blogabissl.blogspot.com/2017/10/listening-to-compter-bugs.html

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