What did computers without screens do?

Paul Koning paulkoning at comcast.net
Mon Dec 14 11:55:20 CST 2015

On Sat, Dec 12, 2015, Mike wrote:
> The one question I do have for the older gentlemen on here is what in the world did the computers without a screen to look at do? Now I know about the tape, cassette tape's and even the paper with the hole punches in them but what kind of applications were they use for? Mathematics or? ? ?

I'll add my perspective.  My first exposure to the use of computers came from my father, who was a mechanical engineering professor at TU Eindhoven, doing precision measurement.  He used the university's computer (there was a single computer serving most of the university's needs) to do analysis of the test results.  For example, one instrument was an interferometer, which would measure positions in terms of wavelength (1/8th of the wavelength of a very stable helium-neon laser).  Those measurements were punched on paper tape by custom hardware, along with temperature and humidity observations.  The software would read those numbers, adjust the measurements to account for temperature (which changes both wavelength and the size of the test object) and humidity (which affects wavelength).  The results could be printed, but often would be shown graphically using a plotter (drum plotter).

A plotter is a pretty simple device, involving a pen that can move across paper in X and Y directions, usually with stepper motors, and a solenoid to raise or lower the pen.  Some had multiple pens (different color or size).  A "flat bed" plotter has an X/Y carriage moving over a flat table on which the paper is mounted.  A drum plotter has a carriage for one axis moving along a drum a few inches diameter, which transports paper (a long roll) in the other direction.

This stuff used the "THE" operating system, an early multi-process operating system and the first to use rigorous design for correctness and clean structure.  User input was via paper tape, for programs and data; output could be paper tape, line printer output, or plotter output.  There were some magnetic tapes as well, I'm not sure how those were used.  The OS used a magnetic drum (similar to a disk drive, older but for those days quite fast) for virtual memory (code and data) and for buffering I/O data streams for paper tape, printer, and plotter.


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