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      Real Programmers write in FORTRAN.<br /><br />     Maybe they do now,<br />     in this decadent era of<br />     Lite beer, hand calculators, and "user-friendly" software<br />     but back in the Good Old Days,<br />     when the term "software" sounded funny<br />     and Real Computers were made out of drums and vacuum tubes,<br />     Real Programmers wrote in machine code.<br />     Not FORTRAN.  Not RATFOR.  Not, even, assembly language.<br />     Machine Code.<br />     Raw, unadorned, inscrutable hexadecimal numbers.<br />     Directly.<br /><br />     Lest a whole new generation of programmers<br />     grow up in ignorance of this glorious past,<br />     I feel duty-bound to describe,<br />     as best I can through the generation gap,<br />     how a Real Programmer wrote code.<br />     I'll call him Mel,<br />     because that was his name.<br /><br />     I first met Mel when I went to work for Royal McBee Computer Corp.,<br />     a now-defunct subsidiary of the typewriter company.<br />     The firm manufactured the LGP-30,<br />     a small, cheap (by the standards of the day)<br />     drum-memory computer,<br />     and had just started to manufacture<br />     the RPC-4000, a much-improved,<br />     bigger, better, faster --- drum-memory computer.<br />     Cores cost too much,<br />     and weren't here to stay, anyway.<br />     (That's why you haven't heard of the company,<br />     or the computer.)<br /><br />     I had been hired to write a FORTRAN compiler<br />     for this new marvel and Mel was my guide to its wonders.<br />     Mel didn't approve of compilers.<br /><br />     "If a program can't rewrite its own code",<br />     he asked, "what good is it?"<br /><br />     Mel had written,<br />     in hexadecimal,<br />     the most popular computer program the company owned.<br />     It ran on the LGP-30<br />     and played blackjack with potential customers<br />     at computer shows.<br />     Its effect was always dramatic.<br />     The LGP-30 booth was packed at every show,<br />     and the IBM salesmen stood around<br />     talking to each other.<br />     Whether or not this actually sold computers<br />     was a question we never discussed.<br /><br />     Mel's job was to re-write<br />     the blackjack program for the RPC-4000.<br />     (Port?  What does that mean?)<br />     The new computer had a one-plus-one<br />     addressing scheme,<br />     in which each machine instruction,<br />     in addition to the operation code<br />     and the address of the needed operand,<br />     had a second address that indicated where, on the revolving drum,<br />     the next instruction was located.<br /><br />     In modern parlance,<br />     every single instruction was followed by a GO TO!<br />     Put *that* in Pascal's pipe and smoke it.<br /><br />     Mel loved the RPC-4000<br />     because he could optimize his code:<br />     that is, locate instructions on the drum<br />     so that just as one finished its job,<br />     the next would be just arriving at the "read head"<br />     and available for immediate execution.<br />     There was a program to do that job,<br />     an "optimizing assembler",<br />     but Mel refused to use it.<br /><br />     "You never know where it's going to put things",<br />     he explained, "so you'd have to use separate constants".<br /><br />     It was a long time before I understood that remark.<br />     Since Mel knew the numerical value<br />     of every operation code,<br />     and assigned his own drum addresses,<br />     every instruction he wrote could also be considered<br />     a numerical constant.<br />     He could pick up an earlier "add" instruction, say,<br />     and multiply by it,<br />     if it had the right numeric value.<br />     His code was not easy for someone else to modify.<br /><br />     I compared Mel's hand-optimized programs<br />     with the same code massaged by the optimizing assembler program,<br />     and Mel's always ran faster.<br />     That was because the "top-down" method of program design<br />     hadn't been invented yet,<br />     and Mel wouldn't have used it anyway.<br />     He wrote the innermost parts of his program loops first,<br />     so they would get first choice<br />     of the optimum address locations on the drum.<br />     The optimizing assembler wasn't smart enough to do it that way.<br /><br />     Mel never wrote time-delay loops, either,<br />     even when the balky Flexowriter<br />     required a delay between output characters to work right.<br />     He just located instructions on the drum<br />     so each successive one was just *past* the read head<br />     when it was needed;<br />     the drum had to execute another complete revolution<br />     to find the next instruction.<br />     He coined an unforgettable term for this procedure.<br />     Although "optimum" is an absolute term,<br />     like "unique", it became common verbal practice<br />     to make it relative:<br />     "not quite optimum" or "less optimum"<br />     or "not very optimum".<br />     Mel called the maximum time-delay locations<br />     the "most pessimum".<br /><br />     After he finished the blackjack program<br />     and got it to run<br />     ("Even the initializer is optimized",<br />     he said proudly),<br />     he got a Change Request from the sales department.<br />     The program used an elegant (optimized)<br />     random number generator<br />     to shuffle the "cards" and deal from the "deck",<br />     and some of the salesmen felt it was too fair,<br />     since sometimes the customers lost.<br />     They wanted Mel to modify the program<br />     so, at the setting of a sense switch on the console,<br />     they could change the odds and let the customer win.<br /><br />     Mel balked.<br />     He felt this was patently dishonest,<br />     which it was,<br />     and that it impinged on his personal integrity as a programmer,<br />     which it did,<br />     so he refused to do it.<br />     The Head Salesman talked to Mel,<br />     as did the Big Boss and, at the boss's urging,<br />     a few Fellow Programmers.<br />     Mel finally gave in and wrote the code,<br />     but he got the test backwards,<br />     and, when the sense switch was turned on,<br />     the program would cheat, winning every time.<br />     Mel was delighted with this,<br />     claiming his subconscious was uncontrollably ethical,<br />     and adamantly refused to fix it.<br /><br />     After Mel had left the company for greener pa$ture$,<br />     the Big Boss asked me to look at the code<br />     and see if I could find the test and reverse it.<br />     Somewhat reluctantly, I agreed to look.<br />     Tracking Mel's code was a real adventure.<br /><br />     I have often felt that programming is an art form,<br />     whose real value can only be appreciated<br />     by another versed in the same arcane art;<br />     there are lovely gems and brilliant coups<br />     hidden from human view and admiration, sometimes forever,<br />     by the very nature of the process.<br />     You can learn a lot about an individual<br />     just by reading through his code,<br />     even in hexadecimal.<br />     Mel was, I think, an unsung genius.<br /><br />     Perhaps my greatest shock came<br />     when I found an innocent loop that had no test in it.<br />     No test.  *None*.<br />     Common sense said it had to be a closed loop,<br />     where the program would circle, forever, endlessly.<br />     Program control passed right through it, however,<br />     and safely out the other side.<br />     It took me two weeks to figure it out.<br /><br />     The RPC-4000 computer had a really modern facility<br />     called an index register.<br />     It allowed the programmer to write a program loop<br />     that used an indexed instruction inside;<br />     each time through,<br />     the number in the index register<br />     was added to the address of that instruction,<br />     so it would refer<br />     to the next datum in a series.<br />     He had only to increment the index register<br />     each time through.<br />     Mel never used it.<br /><br />     Instead, he would pull the instruction into a machine register,<br />     add one to its address,<br />     and store it back.<br />     He would then execute the modified instruction<br />     right from the register.<br />     The loop was written so this additional execution time<br />     was taken into account ---<br />     just as this instruction finished,<br />     the next one was right under the drum's read head,<br />     ready to go.<br />     But the loop had no test in it.<br /><br />     The vital clue came when I noticed<br />     the index register bit,<br />     the bit that lay between the address<br />     and the operation code in the instruction word,<br />     was turned on ---<br />     yet Mel never used the index register,<br />     leaving it zero all the time.<br />     When the light went on it nearly blinded me.<br /><br />     He had located the data he was working on<br />     near the top of memory ---<br />     the largest locations the instructions could address ---<br />     so, after the last datum was handled,<br />     incrementing the instruction address<br />     would make it overflow.<br />     The carry would add one to the<br />     operation code, changing it to the next one in the instruction set:<br />     a jump instruction.<br />     Sure enough, the next program instruction was<br />     in address location zero,<br />     and the program went happily on its way.<br /><br />     I haven't kept in touch with Mel,<br />     so I don't know if he ever gave in to the flood of<br />     change that has washed over programming techniques<br />     since those long-gone days.<br />     I like to think he didn't.<br />     In any event,<br />     I was impressed enough that I quit looking for the<br />     offending test,<br />     telling the Big Boss I couldn't find it.<br />     He didn't seem surprised.<br /><br />     When I left the company,<br />     the blackjack program would still cheat<br />     if you turned on the right sense switch,<br />     and I think that's how it should be.<br />     I didn't feel comfortable<br />     hacking up the code of a Real Programmer.<br /><br />

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