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30Jul/090

The Parable of the Two Programmers

Once upon a time, unbeknownst to each other, the "Automated Accounting Applications Association" and the "Consolidated Computerized Capital Corporation" decided that they needed the identical program to perform a certain service.

Automated hired a programmer-analyst, Alan, to solve their problem.

Meanwhile, Consolidated decided to ask a newly hired entry-level programmer, Charles, to tackle the job, to see if he was as good as he pretended.

Alan, having had experience in difficult programming projects, decided to use the PQR structured design methodology. With this in mind he asked his department manager to assign another three programmers as a programming team. Then the team went to work, churning out preliminary reports and problem analyses.

Back at Consolidated, Charles spent some time thinking about the problem. His fellow employees noticed that Charles often sat with his feet on the desk, drinking coffee. He was occasionally seen at his computer terminal, but his office mate could tell from the rhythmic striking of keys that he was actually
playing Space Invaders.

By now, the team at Automated was starting to write code. The programmers were spending about half their time writing and compiling code, and the rest of their time in conference, discussing the interfaces between the various modules.

His office mate noticed that Charles had finally given up on Space Invaders. Instead he now divided his time between drinking coffee with his feet on the table, and scribbling on little scraps of paper. His scribbling didn't seem to be Tic Tac Toe, but it didn't exactly make much sense, either.

Two months have gone by. The team at Automated finally releases an implementation timetable. In another two months they will have a test version of the program. Then a two month period of testing and enhancing should yield a completed version.

The manager of Charles has by now tired of seeing him goof off. He decides to confront him. But as he walks into Charles's office, he is surprised to see Charles busy entering code at his terminal. He decides to postpone the confrontation, so makes some small talk then leaves. However, he begins to keep a closer watch on Charles, so that when the opportunity presents itself he can confront him. Not looking forward to an unpleasant conversation, he is pleased to notice that Charles seems to be busy most of the time. He has even been see to delay his lunch, and to stay after work two or three days a week.

At the end of three months, Charles announces he has completed the project. He submits a 500 line program. The program appears to be clearly written, and when tested it does everything required in the specifications. In fact it even has a few additional convenience features which might significantly improve the usability of the program. The program is put into test, and, except for one quickly corrected oversight, performs well.

The team at Automated has by now completed two of the four major modules required for their program. These modules are now undergoing testing while the other modules are completed.

After another three weeks, Alan announces that the preliminary version is ready one week ahead of schedule. He supplies a list of the deficiencies that he expects to correct. The program is placed under test. The users find a number of bugs and deficiencies, other than those listed. As Alan explains, this is no surprise. After all this is a preliminary version in which bugs were expected.

After about two more months, the team has completed its production version of the program. It consists of about 2,500 lines of code. When tested it seems to satisfy most of the original specifications. It has omitted one or two features, and is very fussy about the format of its input data. However the company decides to install the program. They can always train their data-entry staff to enter data in the strict format required. The program is handed over to some maintenance programmers to eventually incorporate the missing features.

Sequel:

At first Charles's supervisor was impressed. But as he read through the source code, he realized that the project was really much simpler than he had originally though. It now seemed apparent that this was not much of a challenge even for a beginning programmer.

Charles did produce about 5 lines of code per day. This is perhaps a little above average. However, considering the simplicity of the program, it was nothing exceptional. Also his supervisor remembered his two months of goofing off.

At his next salary review Charles was given a raise which was about half the inflation over the period. He was not given a promotion. After about a year he became discouraged and left Consolidated.

At Automated, Alan was complimented for completing his project on schedule. His supervisor looked over the program. With a few minutes of thumbing through he saw that the company standards about structured programming were being observed. He quickly gave up attempting to read the program however; it seemed quite incomprehensible. He realized by now that the project was really much more complex than he had originally assumed, and he congratulated Alan again on his achievement.

The team had produced over 3 lines of code per programmer per day. This was about average, but, considering the complexity of the problem, could be considered to be exceptional. Alan was given a hefty pay raise, and promoted to Systems Analyst as a reward for his achievement.

30Jul/090

The Story of Mel, a Real Programmer

This was posted to USENET by its author, Ed Nather on May 21, 1983.

"A recent article devoted to the *macho* side of programming 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 GO TO! 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 know 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 programs with the same code massaged by the optimizing assembler 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 located 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 initializer 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 customer 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 by 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 that instruction, so it would refer to the next datum in a series. He had only to increment the index register each time through. Mel never used it.

Instead, he would pull the instruction into 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 execution 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."