Re: What model Apple II did your school have?

[mjmahon@aol.com (Michael J. Mahon)]

Willi Kusche wrote:

>    My "school" was the USAF.  I enlisted in January of 1959.  That
>fall I was sent to a programming class run by IBM.  The computer?  An
>IBM 650.

One of the first "affordable" computers--and with vacuum tubes!

The 650 was also Don Knuth's first computer--or at least the
one that he spent the most time with at the Case Institute
of Technology.

Don tells a great story about the night he was babysitting a
computation while reading, and, out of the corner of his eye,
he noticed that the 650's console lights seemed to be
flickering more slowly.  He dismissed it as an illusion and
went on with his reading.

Several minutes later, he noticed it again, and this time the
lights _did_ seem to be perceptibly slowing down...

It turned out that the magnetic drum motor had failed, and the
drum, which implemented all the computer's registers and
storage, and also supplied the clock to the computer, was
slowly spinning down, and lowering the speed of the computer
with it.  The inertia of the drum was such that it took a long time
to stop, and the margins on the read signals were such that
the computer continued to operate correctly for a good fraction
of the spin-down time.

My first computer was an IBM 1620 at St. Louis University.
It was the continuation of the trend to lower priced computers,
and was one of the earliest commercial "transistorized"
computers.  My introduction to it was through FORTRAN,
but within a week I had discovered its machine language.

Like the 650, it was a decimal machine.  But the 1620 was
a variable-field-length, storage-to-storage architecture, while
the 650 was a word-oriented, accumulator architecture.

My second "personal" computer--in that, like the 1620, I
was able to use it personally and interactively, was the
Burroughs 220.  It was available for grad student sign-up
because it had been obsoleted by Caltech's IBM 7090.
(I've often said that the most interesting computer research
used to be done on machines considered obsolete.  ;-)

The 220 was the last commercial vacuum tube machine,
and it had many modern niceties:  an index register,
floating-point arithmetic (BCD), a fast (and awful!)
electrostatic printer...  But the main thing it had was
a glorious interactive console, with every register's
contents displayed and changeable at the touch of
a button.  It even had a data address/code address
"breakpoint" register that could be used while sitting
at the eye-filling console!  (Of course, a downside to
any vacuum tube machine is that it required a full-time
technician to keep it running smoothly, and every week
or so, it would be down for a morning...)

Ahh, the joy of sitting at that console at 2 a.m., debugging
code and bringing it to life!

-michael

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