August 8, 2004

• Thanks for the Memory

  The first computer I had anything to do with used vacuum tubes instead of integrated circuits. Many of you have never seen a vacuum tube. They are about the size of an elongated light bulb and produce just about as much heat as a light bulb does. The computer was physically large, taking up three stories of one wing of the building it was in. The large number of vacuum tubes meant that failures were frequent, and the computer usually ran for about twenty minutes before something burned out and had to be replaced. Input and output were by punched cards, and the program had to be able to read in, read the data, perform all the calculations and produce its output in twenty minutes.

  The computer's speed was glacially slow by today's standards. Programming for it was an art, as there were no compilers or assemblers, only machine language. The memory used acoustic delay lines -- eight tanks of mercury, each almost twenty feet long, with a sonar transducer at each end -- and instructions had to be interspersed with data in such a way as to make the data available at the best possible time for the calculations being performed.

  There was a total of four kilobytes of memory in a space twenty feet long by ten feet wide, shock mounted and insulated against outside noise and vibration.

  I have seen, but have not used, the old eight inch floppy disks. The first machine I had with a floppy drive used single sided 5.25 inch floppies, each with a capacity of 180 kilobytes of storage. That's 45 times as much storage as that first commercial computer I used, and it took up less space than half a page of paper.

  Floppies continued to grow in capacity, first going double sided, then going to high density. Then the 5.25 inch floppies were replaced by the 3.5 inch floppies with a capacity of 1.44 megabytes, eight times the capacity of the first floppies.

  Some of you have never seen a 5.25 inch floppy. The 3.5 inch floppies have started to disappear.

  Now there are CD-ROMs and DVD-ROMs. The DVDs will soon be going to multiple layers for increased capacity.

  Meanwhile, hard drives have improved to the point that the home user can economically have a terabyte of storage in his computer.

  I keep all of my writings on a small memory device about the size of three cigarettes placed side by side. It is so small I keep it on a cord, a long shoelace, to keep from losing it. It contains 256 megabytes of storage, almost 178 times the capacity of a 3.5 inch floppy. That's 65,536 times the capacity of that old computer whose memory was the size of a living room, the first computer I worked with just 45 years ago.

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