🚀 go-pugleaf

I must apologise for two things:  first, I don't read this newsgroup
so if this has appeared before, sorry; second, I have no idea who
wrote this, as I found it on a bulletin board about 10 years ago and
only rediscovered it in my archives recently, so sorry to whoever wrote
it for no author credit.

I think this is a lovely story that even outdoes "Real Programmers..."
------------------
A recent article devoted to the macho side of programming ("Real
Programmers Don't Use Pascal") made the bald and unvarnished
statement:
          Real programmers write in Fortran

Maybe they do now, in this decadent era of Lite beer, hand calculators
and "user-friendly" software, but back in the Good Old Days, when the
term "software" sounded funny and Real Computers were made out of
drums and vacuum tubes, Real Programmers wrote in machine code. 
Not Fortran.  Not RATFOR.  Not even assembly language.  Machine
code.  Raw, unadorned, inscrutable, hexadecimal numbers.  Directly.

Lest a whole new generation of programmers grow up in ignorance of
this glorious past, I feel duty bound to describe, as best I can through
the generation gap, how a Real Programmer wrote code.  I'll call him
Mel, because that was his name.

I first met Mel when I went to work for Royal McBee Computer Corp.,
a now-defunct subsidiary of the typewriter company.  The firm
manufactured the LGP-30, a small, cheap (by the standards of the day)
drum-memory computer, and had just started to manufacture the RPC-
4000, a much improved, bigger, better, faster -- drum memory computer. 
Cores cost too much, and weren't here to stay, anyway.  (That's why
you haven't heard of the company, or the computer.)

I had been hired to write a Fortran compiler for this new marvel and
Mel was my guide to its wonders.  Mel didn't approve of compilers.

If a program can't rewrite its own code", he asked, "what good is it?"

Mel had written in hexadecimal, the most popular computer program the
company owned.  It ran on the LGP-30 and played blackjack with
potential customers at computer shows.  Its effect was always dramatic. 
The LGP-30 booth was packed at every show, and the IBM salesmen
stood around talking to each other.  Whether or not this actually sold
computers was a question we never discussed.

Mel's job was to re-write the blackjack program for the RPC-4000. 
(Port?  What does that mean?)  The new computer had a one-plus-one
addressing scheme, in which each machine instruction, in addition to the
operation code and the address of the needed operand, had a second
address that indicated where, on the revolving drum, the next instruction
was located.  In modern parlance, every single instruction was followed
by a GOTO!  Put that in Pascal's pipe and smoke it.

Mel loved the RPC-4000 because he could optimize his code: that is,
locate instructions on the drum so that just as one finished its job, the
next would be just arriving at the "read head" and available for
immediate execution.  There was a program to do that job, an
"optimizing assembler", but Mel refused to use it.

"You never knew where it's going to put things," he explained, "so
you'd have to use separate constants."

It was a long time before I understood that remark.  Since Mel knew the
numerical value of every operation code, and assigned his own drum
addresses, every instruction he wrote could also be considered a
numerical constant.  He could pick up an earlier "add" instruction, say,
and multiply by it, if it had the right numeric value.  His code was not
easy for someone else to modify.

I compared Mel's hand-optimized program with the same code massaged
by the optimizing assembly program, and Mel's always ran faster.  That
was because the "top-down" method of program design hadn't been
invented yet, and Mel wouldn't have used it anyway.  He wrote the
innermost parts of his program loops first, so they would get first choice
of the optimum address locations on the drum.  The optimizing
assembler wasn't smart enough to do it that way.

Mel never wrote time-delay loops, either, even when the balky
Flexowriter required a delay between output characters to work right. 
He just locate instructions on the drum so each successive one was just
past the read head when it was needed; the drum had to execute another
complete revolution to find the next instruction.  He coined an
unforgettable term for this procedure.  Although "optimum" is an
absolute term, like "unique", it became common verbal practice to make
it relative: "not quite optimum" or "less optimum" or "not very
optimum".  Mel called the maximum time-delay locations the "most
pessimum".

After he finished the blackjack program and got it to run, ("Even the
initialiser is optimized", he said proudly) he got a Change Request from
the sales department.  The program used an elegant (optimized) random
number generator to shuffle the "cards" and deal from the "deck", and
some of the salesmen felt it was too fair, since sometimes the customers
lost.  They wanted Mel to modify the program so, at the setting of a
sense switch on the console, they could change the odds and let the
customers win.

Mel balked.  He felt this was patently dishonest, which it was, and that
it impinged on his personal integrity as a programmer, which it did, so
he refused to do it.  The Head Salesman talked to Mel, as did the Big
Boss and, at the boss's urging, a few Fellow Programmers.  Mel finally
gave in and wrote the code, but he got the test backwards and, when the
sense switch was turned on, the program would cheat, winning every
time.  Mel was delighted with this, claiming his subconscious was
uncontrollably ethical, and adamantly refused to fix it.

After Mel had left the company for greener pa$ture$, the Big Boss
asked me to look at the code and see if I could find the test and reverse
it.  Somewhat reluctantly, I agreed to look.  Tracking Mel's code was
a real adventure.

I have often felt that programming is an art form, whose real value can
only be appreciated by another versed in the same arcane art; there are
lovely gems and brilliant coups hidden from human view and
admiration, sometimes forever, by the very nature of the process.  You
can learn a lot about an individual just be reading through his code, even
in hexadecimal.  Mel was, I think, an unsung genius.

Perhaps my greatest shock came when I found an innocent loop that had
no test in it.  No test.  None.  Common sense said it had to be a closed
loop, where the program would circle forever, endlessly.  Program
control passed right through it, however, and safely out the other side. 
It took me two weeks to figure it out.

The RPC-4000 computer had a really modern facility called an index
register.  It allowed the programmer to write a program loop that used
an indexed instruction inside; each time through, the number in the index
register was added to the address of the instruction, so it would refer to
the next datum in a series.  Mel never used it.

Instead, he would pull the instruction in a machine register, add one to
its address, and store it back.  He would then execute the modified
instruction right from the register.  The loop was written so this
additional instruction time was taken into account -- just as this
instruction finished, the next one was right under the drum's read head,
ready to go.  But the loop had no test in it.

The vital clue came when I noticed the index register bit, the bit that lay
between the address and the operation code in the instruction word, was
turned on -- yet Mel never used the index register, leaving it zero all the
time.  When the light went on it nearly blinded me.

He had located the data he was working on near the top of memory --
the largest locations the instructions could address -- so, after the last
datum was handled, incrementing the instruction address would make it
overflow.  The carry would add one to the operation code, changing it
to the next one in the instruction set: a jump instruction.  Sure enough,
the next program instruction was in address location zero, and the
program went happily on its way.

I haven't kept in touch with Mel, so I don't know if he ever gave in to
the flood of change that has washed over programming techniques since
those long-gone days.  I like to think he didn't.  In any event, I was
impressed enough that I quit looking for the offending test, telling the
Big Boss I couldn't find it.  He didn't seem surprised.  When I left the
company, the blackjack program would still cheat if you turned on the
right sense switch, and I think that's how it should be.  I didn't feel
comfortable hacking up the code of a Real Programmer.
-----
Mark Kosten,           phone: +61 3 479-2767
Computer Centre,       AARNet (internet): cc...@lure.latrobe.edu.au
La Trobe University,   ACSnet: cc...@lure.lat.oz.au
Bundoora, 3083         X.25 (PSI): 2347300000::ccmk
Australia