#software fail

I AM GOING TO THE LAND OF FUCK YOU, THIS SHIT IS INTERESTING.

FuCK. THE uNDISCOVERED COuNTRY. FROM WHOSE BOuRN NO TRAVELER SHALL RETuRN. —OW!

WHAT DID I SAY ABOUT SHAKESPEARING AT ME. NOW HUSH, SIT THERE AND BE GOOD WHILE I UNLOAD A GREAT STEAMING VAT OF KNOWLEDGE ALL OVER ‘littlepinkbeast.’ RIVULETS OF PEDAGOGY WILL BRIM AND SPILL OVER. THERE WILL BE WISDOM ALL OVER THE FUCKING PLACE.

I’LL CALL THE CARPET CLEANING PLACE. AND TELL THEM TO BE ON STANDBY.

YOU ARE NOT AS FUNNY AS YOU THINK YOU ARE. ANYWAY.

WHEN THE OPERATOR REACHED THE COMMAND LINE AFTER ENTERING THE WRONG DATA, IT TOLD THE MACHINE THAT DATA ENTRY WAS COMPLETE AND IT COULD MOVE ON TO THE NEXT PHASE. HOWEVER, SHE WENT BACK UP THE SCREEN TO FIX THE ERROR AND THEN RETURNED TO THE COMMAND LINE IN UNDER 8 SECONDS.

WHICH HAPPENS TO BE ABOUT AS LONG AS THE THERAC-25 TAKES TO SET THE BENDING MAGNETS IT USES TO SHAPE AND CONTROL THE X-RAY BEAM.

BECAUSE OF THE WAY THE TASKS AND SUBROUTINES ARE SCHEDULED, IF EDITS ARE MADE WITHIN THAT EIGHT SECONDS, THE DATA ENTRY SUBROUTINE WILL NOT DETECT THAT THEY HAVE OCCURRED.

WORSE, THE DATA ENTRY COMPLETION VARIABLE ONLY MARKS THAT THE CURSOR HAS BEEN DOWN TO THE COMMAND LINE, NOT THAT IT IS STILL THERE. IT WAS SET BY THE OPERATOR WHEN SHE FINISHED ENTERING THE DATA THE FIRST TIME, SETTING THE WRONG TREATMENT MODE.

THE OTHER SET OF ACCIDENTS INVOLVED A COMPLETELY DIFFERENT OVERSIGHT INVOLVING THE SOFTWARE CONTROLLING THE ROTATION OF THE TREATMENT HEAD'S TURNTABLE. THE THERAC-25 TURNTABLE HAD THREE POSITIONS: ELECTRON BEAM, X-RAY BEAM, AND FIELD LIGHT. IN BOTH TREATMENT POSITIONS, IT HAD SOME PRETTY VITAL ACCESSORY EQUIPMENT TO MODULATE AND SHAPE THE BEAM. IF YOU DIDN'T HAVE THIS SHIT IN PLACE WHEN YOU TURNED IT ON, YOU WERE BASICALLY POURING THE FULL RAW POWER OF THE BEAM DOWN ON WHATEVER WAS UNDERNEATH IT. REMEMBER THAT IN X-RAY MODE THE BEAM ENERGY WAS SET TO 25 MeV. THAT'S A LOT, BY THE WAY.

THE TURNTABLE WAS MANEUVERED INTO POSITION BY THE COMPUTER. THREE MICROSWITCHES REGISTERED ITS POSITION AND SENT THE INFORMATION BACK TO THE COMPUTER. THE SOFTWARE RESPONSIBLE FOR CHECKING THAT THE HEAD WAS IN THE RIGHT POSITION RELIED ON THE VALUE OF A GIVEN VARIABLE: IF DURING ANY POINT IN THIS SETUP ROUTINE THAT VARIABLE WAS ZERO, IT INDICATED THAT EVERYTHING WAS IN THE RIGHT PLACE. ANY NONZERO VALUE MEANT THAT THINGS WERE STILL BEING ADJUSTED AND TREATMENT COULD NOT PROCEED. 

PROBLEM WAS THAT THE VARIABLE IN QUESTION WAS ONLY ONE BYTE. IT COULD ONLY CONTAIN DECIMAL VALUES UP TO 255. EVERY TIME THIS BIT OF CODE RAN, THE VALUE WENT UP BY ONE. SO AFTER TWO HUNDRED AND FIFTY-FIVE TRIPS THROUGH THIS ROUTINE, THE VARIABLE ROLLED OVER TO ZERO, THE WAY A CAR'S ODOMETER WILL GO FROM 999,999 TO 000.000. IF THE OPERATOR SET THE MACHINE AT THIS EXACT MOMENT, AND THE TURNTABLE WAS IN THE WRONG PLACE, THE SOFTWARE WOULD NOT NOTICE THE PROBLEM OR PREVENT THE BEAM TURNING ON.

YOu'RE SAYING. THAT THEY DIDN'T NOTICE THAT THIS WAS A GIGANTIC FuCKING SAFETY CONCERN. WHEN THEY WROTE THIS SOFTWARE.

I AM INDEED.

ANYWAY, TO GET BACK TO THE ACTUAL QUESTION. HOW SOMETHING LIKE THIS COULD MAKE IT TO PRODUCTION WITHOUT ANYBODY POINTING OUT THAT IT WAS LIKELY TO FRY PEOPLE INSTEAD OF TUMORS IS A FUNCTION OF A NUMBER OF DIFFERENT OVERSIGHTS. FIRST OFF, THE THERAC-25 SOFTWARE WAS BASED OFF CODE USED TO RUN THE THERAC-20 AND THERAC-6 MACHINES, RATHER THAN BEING WRITTEN FROM SCRATCH. THESE EARLIER MACHINES HAD HARDWARE SAFETY INTERLOCKS, SO THE SOFTWARE WASN'T RELIED UPON TOTALLY TO KEEP SHIT WHERE IT SHOULD BE; THEREFORE, IT WASN'T REALLY WRITTEN WITH THAT IN MIND. SECONDLY, THE SOFTWARE DEVELOPERS DIDN'T TAKE INTO ACCOUNT "IMPROBABLE" KEYSTROKE SEQUENCES SUCH AS THE HIGHLY-PRACTICED OPERATOR'S RAPID TYPING. THIRDLY, THE INTERFACE WITH THE OPERATOR WAS UNHELPFUL AS FUCK AND JUST SAID THINGS LIKE "MALFUNCTION 54" INSTEAD OF "MODE/SETTING DISAGREE."

TELL ME THEY FIXED THIS.

KIND OF. EVENTUALLY. AFTER A HELL OF A LOT OF BACK AND FORTH BETWEEN THE COMPANY THAT MADE THE THERAC-25 AND THE FDA, FIXES WERE PUT IN PLACE. BUT SIX PEOPLE WERE MASSIVELY OVERDOSED. AT LEAST THREE OF THEM DIED AS A DIRECT RESULT. AND UNFORTUNATELY THIS KIND OF THING--FOR REASONS INCLUDING HUMAN ERROR AND SOFTWARE FLAWS--HAS HAPPENED AGAIN SINCE THE 1980S. IT PROBABLY WILL KEEP HAPPENING.

ALSO. HOW DO YOu KNOW ALL THIS.

THE SAME REASON YOU KNOW ABOUT WEATHER SHIT.

RESEARCH BONERS.

AND A CHRONIC CASE OF FASCINATION WITH DISASTER, BUT THAT'S PRETTY MUCH A JOB REQUIREMENT.

I'M DEPRESSED NOW. TELL ME SOMETHING THAT ISN'T DEPRESSING. KARKAT. SOMETHING ENTERTAINING.

*SIGH* FINE. GO FIND ME THE BIG BOOK OF MONTY PYTHON SCRIPTS.

WILL YOu DO. THE CHEESE SHOP ONE.