Charles Sheffield - Georgia On My Mind

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Georgia On My Mind

by Charles Sheffield

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First published in Analog, January 1993

Fictionwise Contemporary

Science Fiction

Hugo Award Winner; Nebula Award Winner

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I first tangled with digital computers late in 1958. That may sound

like the dark ages, but we considered ourselves infinitely more advanced than

our predecessors of a decade earlier, when programming was done mostly by

sticking plugs into plug-boards and a card-sequenced programmable calculator

was held to be the height of sophistication.

Even so, 1958 was still early enough that the argument between analog

and digital computers had not yet been settled, decisively, in favor of the

digital. And the first computer that I programmed was, by anyone's standards,

a brute.

It was called DEUCE, which stood for Digital Electronic Universal

Computing Engine, and it was, reasonably enough to card players, the next

thing after the ACE (for Automatic Computing Engine), developed by the

National Physical Laboratory at Teddington. Unlike ACE, DEUCE was a commercial

machine; and some idea of its possible shortcomings is provided by one of the

designers' comments about ACE itself: "If we had known that it was going to be

developed commercially, we would have finished it."

DEUCE was big enough to walk inside. The engineers would do that,

tapping at suspect vacuum tubes with a screwdriver when the whole beast was

proving balky. Which was often. Machine errors were as common a cause of

trouble as programming errors; and programming errors were dreadfully

frequent, because we were working at a level so close to basic machine logic

that it is hard to imagine it today.

I was about to say that the computer had no compilers or assemblers,

but that is not strictly true. There was a floating-point compiler known as

ALPHACODE, but it ran a thousand times slower than a machine code program and

no one with any self-respect ever used it. We programmed in absolute, to make

the best possible use of the machine's 402 words of high-speed (mercury delay

line) memory, and its 8,192 words of back-up (rotating drum) memory. Anything

needing more than that had to use punched cards as intermediate storage, with

the programmer standing by to shovel them from the output hopper back into the

input hopper.

When I add that binary-to-decimal conversion routines were usually

avoided because they wasted space, that all instructions were defined in

binary, that programmers therefore had to be very familiar with the binary

representation of numbers, that we did our own card punching with hand (not

electric) punches, and that the machine itself, for some reason that still

remains obscure to me, worked with binary numbers whose most significant digit

was on the _right_, rather than on the left -- so that 13, for example, became

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1011, rather than the usual 1101 -- well, by this time the general flavor of

DEUCE programming ought to be coming through.

Now, I mention these things not because they are interesting (to the

few) or because they are dull (to the many) but to make the point that anyone

programming DEUCE in those far-off days was an individual not to be taken

lightly. We at least thought so, though I suspect that to higher management we

were all hare-brained children who did incomprehensible things, many of them

in the middle of the night (when de-bug time was more easily to be had).

A few years later more computers became available, the diaspora

inevitably took place, and we all went off to other interesting places. Some

found their way to university professorships, some into commerce, and many to

foreign parts. But we did tend to keep in touch, because those early days had

generated a special feeling.

One of the most interesting characters was Bill Rigley. He was a tall,

dashing, wavy-haired fellow who wore English tweeds and spoke with the open

"a" sound that to most Americans indicates a Boston origin. But Bill was a New

Zealander, who had seen at first hand things like the Great Barrier Reef, that

the rest of us had barely heard of. He didn't talk much about his home and

family, but he must have pined for them, because after a few years in Europe

and America he went back to take a faculty position in the Department of

Mathematics (and later the Computer Science Department, when one was finally

created) at the University of Auckland.

Auckland is on the north island, a bit less remote than the bleaker

south island, but a long way from the East Coast of the United States, where I

had put down my own roots. Even so, Bill and I kept in close contact, because

our scientific interests were very similar. We saw each other every few years

in Stanford, or London, or wherever else our paths intersected, and we knew

each other at the deep level where few people touch. It was Bill who helped me

to mourn when my wife, Eileen, died, and I in turn knew (but never talked

about) the dark secret that had scarred Bill's own life. No matter how long we

had been separated, our conversations when we met picked up as though they had

never left off.

Bill's interests were encyclopedic, and he had a special fondness for

scientific history. So it was no surprise that when he went back to New

Zealand he would wander around there, examining its contribution to world

science. What was a surprise to me was a letter from him a few months ago,

stating that in a farm-house near Dunedin, towards the south end of the south

island, he had come across some bits and pieces of Charles Babbage's

Analytical Engine.

Even back in the late 1950's, we had known all about Babbage. There was

at the time only one decent book about digital computers, Bowden's "Faster

Than Thought," but its first chapter talked all about that eccentric but

formidable Englishman, with his hatred of street musicians and his low opinion

of the Royal Society (existing only to hold dinners, he said, at which they

gave each other medals). Despite these odd views, Babbage was still our patron

saint. For starting in 1834 and continuing for the rest of his life, he tried

-- unsuccessfully -- to build the world's first programmable digital computer.

He understood the principles perfectly well, but he was thwarted because he

had to work with mechanical parts. Can you imagine a computer built of cogs

and toothed cylinders and gears and springs and levers?

Babbage could. And he might have triumphed even over the inadequacy of

the available technology, but for one fatal problem: he kept thinking of

improvements. As soon as a design was half assembled, he would want to tear it

apart and start using the bits to build something better. At the time of

Babbage's death in 1871, his wonderful Analytical Engine was still a dream.

The bits and pieces were carted off to London's Kensington Science Museum,

where they remain today.

Given our early exposure to Babbage, my reaction to Bill Rigley's

letter was pure skepticism. It was understandable that Bill would _want_ to

find evidence of parts of the Analytical Engine somewhere on his home

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stamping-ground; but his claim to have done so was surely self-delusion.

I wrote back, suggesting this in as tactful a way as I could; and

received in prompt reply not recantation, but the most extraordinary package

of documents I had ever seen in my life (I should say, to that point; there

were stranger to come).

The first was a letter from Bill, explaining in his usual blunt way

that the machinery he had found had survived on the south island of New

Zealand because "we don't chuck good stuff away, the way you lot do." He also

pointed out, through dozens of examples, that in the nineteenth century there

was much more contact between Britain and its antipodes than I had ever

dreamed. A visit to Australia and New Zealand was common among educated

persons, a kind of expanded version of the European Grand Tour. Charles Darwin

was of course a visitor, on the _Beagle_, but so also were scores of less

well-known scientists, world travelers, and gentlemen of the leisured class.

Two of Charles Babbage's own sons were there in the 1850's.

The second item in the package was a batch of photographs of the

machinery that Bill had found. It looked to me like what it was, a bunch of

toothed cylinders and gears and wheels. They certainly resembled parts of the

Analytical Engine, or the earlier Difference Machine, although I could not see

how they might fit together.

Neither the letter nor the photographs were persuasive. Rather the

opposite. I started to write in my mind the letter that said as much, but I

hesitated for one reason: many historians of science know a lot more history

than science, and few are trained computer specialists. But Bill was the other

way round, the computer expert who happened to be fascinated by scientific

history. It would be awfully hard to fool him -- unless he chose to fool

himself.

So I had another difficult letter to write. But I was spared the

trouble, for what I could not dismiss or misunderstand was the third item in

the package. It was a copy of a programming manual, hand-written, for the

Babbage Analytical Engine. It was dated July 7, 1854. Bill said that he had

the original in his possession. He also told me that I was the only person who

knew of his discovery, and he asked me to keep it to myself.

And here, to explain my astonishment, I have to dip again into computer

history. Not merely to the late 1950's, where we started, but all the way to

1840. In that year an Italian mathematician, Luigi Federico Menabrea, heard

Babbage talk in Turin about the new machine that he was building. After more

explanations by letter from Babbage, Menabrea wrote a paper on the Analytical

Engine, in French, which was published in 1842. And late that year Ada

Lovelace (Lord Byron's daughter; Lady Augusta Ada Byron Lovelace, to give her

complete name) translated Menabrea's memoir, and added her own lengthy notes.

Those notes formed the world's first software manual; Ada Lovelace described

how to program the Analytical Engine, including the tricky techniques of

recursion, looping, and branching.

So, twelve years before 1854, a programming manual for the Analytical

Engine existed; and one could argue that what Bill had found in New Zealand

was no more than a copy of the one written in 1842 by Ada Lovelace.

But there were problems. The document that Bill sent me went far beyond

the 1842 notes. It tackled the difficult topics of indirect addressing,

re-locatable programs and subroutines, and it offered a new language for

programming the Analytical Engine -- what amounted to a primitive assembler.

Ada Lovelace just might have entertained such advanced ideas, and

written such a manual. It is possible that she had the talent, although all

signs of her own mathematical notebooks have been lost. But she died in 1852,

and there was no evidence in any of her surviving works that she ever blazed

the astonishing trail defined in the document that I received from Bill.

Furthermore, the manual bore on its first page the author's initials, L.D. Ada

Lovelace for her published work had used her own initials, A.A.L.

I read the manual, over and over, particularly the final section. It

contained a sample program, for the computation of the volume of an irregular

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Charles Sheffield - Georgia On My Mind

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