ONE OF THE EARLIEST MACHINES to be accepted as an analog
computer is the Antikythera Mechanism. Dated to around 100 BC,
it was used in astronomy to determine the positions of celestial
bodies decades in advance. Only fragments of it remain, but
detailed imaging suggests it could even model the irregular orbit of
the moon. You can find a simulation of the Antikythera Mechanism
at http://www.etl.uom.gr/mr/index.php?mypage=antikythera_sim. It
only has a Windows executable, but it runs under Wine.
In the 13th century, we find Turkish inventor Ismail al-Jazari
and his automata, laid out in his Book of Knowledge of Ingenious
Mechanical Devices. Al-Jazari made complex mechanical
musicians that ran via clockwork, and even had a programmable
drum machine, coded by altering the movement of cams. However,COMPUTING PRE-HISTORY
Defining the earliest “computer” is tricky, but they’ve
certainly been around for longer than you might think
Imagine your processor starting a calculation on one side of the
room and finishing on the other, all run by cogs.WHERE’S ALAN TURING?
Babbage’s machines were analog, but for digital computers,
history usually looks to Alan Turing. You probably know
the story well—how Alan Turing cracked the Germans’
Enigma code so that Benedict Cumberbatch could save
England (according to the film The Imitation Game). But
this simplified version of events gives the impression that
Turing was behind all the computer design and Nazi code-
breaking. That’s not really the case. The Enigma codes were
indeed broken with the aid of a machine called the Bombe,
designed by Turing and Gordon Welchman, thus helping to
defeat the German navy.
The ultimate target was the coding for the more
advanced Lorenz machine, used by the German high
command, and even Hitler himself. Although Turing
influenced what was built, it was actually an unsung hero,
telephone engineer Tommy Flowers, who was behind the
design and construction of Colossus—and out of his own
pocket, no less.
The computer needed to be built using valves and
switches. This made it enormous—as big as a room—
presumably leading to its name. With the first model
being built in 1943, the Colossus is regarded as the first
programmable digital electronic computer. You can run
your own online at http://www.virtualcolossus.co.uk.documentaries usually start just before the Victorian era. In
those days the word “computer” would have evoked an image of
a guy with a pencil behind his ear doing math. But these squishy
creatures were unreliable at best, and a machine with unerring
accuracy was needed for a genuine technical revolution.SPLIT THE DIFFERENCE
Enter Charles Babbage (1791-1871) and his Difference Engine.
This was a mechanical number-cruncher, powered by a hand
crank, with digits shown on rotating dials. It could not only perform
arithmetic, but could also be programmed to follow numeric
sequences, and even extract the root of a quadratic equation.
Babbage also designed the Analytical Engine, though it was
never built. This would have been so far ahead of its time that it’s
almost scary, with features much like a mainframe computer of
the mid 20th century: punch-card programming, 16.2K of decimal
storage, a grid layout with its own internal procedures, like a CPU
dubbed “The Mill,” and something akin to assembly language.
Unfortunately, withdrawn funding meant the Difference
Engine was never completed (Babbage only made a stripped-
down prototype), and there was no interest in producing the even
more elaborate Analytical Engine. Nevertheless, enough design
existed for Babbage’s friend Ada Lovelace to write an algorithm
for it, thus Lovelace is generally credited as having written the
first computer program.
Victorian Britain may not have been interested in completing
the Difference Engine, but thankfully modern Britain is. If you
want to try out the Difference Engine, there are some simulations
online, and a Python script on GitHub if you want to look for them.
If you want to see it in the metal, as it were, the Science Museum
in London has an operational section on display. Meanwhile,
the Analytical Engine is currently being built by the Plan28
organization—see http://plan28.org for more info.A Colossus Mark 2 being operated by British Wrens.so retro
26 MAXIMUMPC JUN 2019 maximumpc.com