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U
         ┬┘╘┼╙: ╙╘╥╔╬╟ ╙╨┼┼─

           BY ═AURICE ╩ONES

    ╧N ╠╧┴─╙╘┴╥ #210 ╔ DESCRIBED HOW
ARRAY VARIABLES AND SIMPLE VARIABLES
WERE STORED. ╔N THE CASE OF STRING
VARIABLES ONLY THE NAME, LENGTH, AND
TWO POINTERS ARE STORED. ╘HE POINTERS
SHOW WHERE THE STRING IS STORED. ╘HE
ACTUAL STRINGS ARE STORED EITHER IN
THE CODE OR AT THE TOP OF ┬┴╙╔├ ╥┴═,
EXTENDING DOWNWARD. ╘HIS LATTER METHOD
OF STORAGE LEADS TO THE TOPIC OF
GARBAGE COLLECTION.

    ╔F THE STRING APPEARS IN THE CODE,
THE POINTERS WILL POINT INTO THE CODE,
AND NO NEW MEMORY WILL BE NEEDED.
╙TRINGS CREATED BY STATEMENTS SUCH AS
┴$="╘HIS IS A STRING" AND STRINGS READ
FROM DATA STATEMENTS WILL BE STORED
THIS WAY.

    ╙TRINGS INTRODUCED INTO THE
PROGRAM BY ╟┼╘, ╙╘╥$, OR BY
CALCULATION, SUCH AS ┴$=├$+─$, ARE
STORED AT THE TOP OF ┬┴╙╔├ ╥┴═. ┼ACH
SUCCESSIVE STRING IS STORED IN THE
FIRST FREE AREA CONTAINING ENOUGH ROOM
FOR THE ENTIRE STRING. ╘HIS PROCESS
CONTINUES UNTIL THE COMPUTER FINDS
THAT THE SPACE BETWEEN THE LAST STRING
AND THE TOP OF ARRAYS IS TOO SMALL FOR
THE CURRENT STRING.

    ╫HEN THIS HAPPENS, THE GARBAGE
COLLECTION ROUTINE ATTEMPTS TO
REORGANIZE THE SPACE ABOVE ARRAYS.

    ╘O SEE WHY IT MAY BE POSSIBLE TO
REORGANIZE THE SPACE WITHOUT LOSING
VARIABLES, CONSIDER A PROGRAM WHICH
USES ┴$ AND ┬$ OVER AND OVER. ╙UPPOSE
THAT EACH IS STORED IN HIGH MEMORY AND
EACH TAKES ON THESE VALUES IN THIS
ORDER: ┴$ IS"├┴╘", ┴$ IS "┬╔╥─", ┬$ IS
"╬╒═┬┼╥" AND FINALLY ┬$ IS "╠┼╘╘┼╥."
╘HE TOP OF MEMORY WILL NOW CONTAIN:

         ╠┼╘╘┼╥╬╒═┬┼╥┬╔╥─├┴╘

    ╔F THE GARBAGE COLLECTION ROUTINE
IS USED, THE COMPUTER WILL LOOK AT THE
POINTERS OF ALL VARIABLES AND SELECT
THE ONE NEAREST THE TOP OF ╥┴═. ╔N
THIS CASE, IT IS ┴$ AND THE POINTERS
INDICATE THE START OF ┬╔╥─, THE
CURRENT VALUE OF ┴$. ╙INCE THIS IS THE
HIGHEST ADDRESS FOUND, ANY STRING
ABOVE HERE IS NO LONGER NEEDED SO THE
COMPUTER MOVES ┬╔╥─ TO THE TOP AND THE
MEMORY NOW CONTAINS:

         ╠┼╘╘┼╥╬╒═┬┼╥┬╔╥┬╔╥─

    ╘HE ROUTINE NOW LOOKS THROUGH THE
ENTIRE LIST AGAIN, DECIDING WHICH
POINTER POINTS TO NEXT HIGHEST MEMORY
LOCATION. ╔N OUR EXAMPLE THERE IS ONLY
ONE STRING LEFT, ┬$. ╘HE CURRENT VALUE
OF ┬$ IS ╠┼╘╘┼╥, SO THIS IS MOVED TO
THE NEXT SPACE AFTER THE NEW POSITION
OF ┴$ AND THE MEMORY LOOKS LIKE THIS:

         ╠┼╘╘┼╥╬╒═╠┼╘╘┼╥┬╔╥─

    ╘HE POINTER WHICH INDICATES THE
BOTTOM OF STRINGS IS NOW SET TO THE
SPACE WHERE THE NEWLY PLACED ╠┼╘╘┼╥
STARTS. ╘HE OLD VALUES ARE NOT ERASED
BUT WILL BE OVERWRITTEN BY THE NEXT
STRING.

    ╙IMPLE ENOUGH, BUT IF THE NUMBER
OF VARIABLES IS LARGE, THE PROCESS CAN
BE TIME CONSUMING. ╙INCE THE SIMPLE
VARIABLES AND THE ARRAY VARIABLES MAY
CONTAIN STRINGS, ALL OF THESE AREAS
MUST BE SEARCHED COMPLETELY ╞╧╥ ┼┴├╚
╓┴╥╔┴┬╠┼. ╔F THERE ARE 100 VARIABLES,
EACH WILL BE LOOKED AT MANY TIMES, AND
MORE TIME WILL BE REQUIRED TO MOVE
EACH STRING.

    ╬OTICE THAT THE ROUTINE WORKS WITH
POINTERS AND LENGTH OF STRING UNTIL
THE ACTUAL MOVE IS MADE. ┼VEN THEN,
THESE NUMBERS ALLOW THE STRING TO BE
MOVED EFFICIENTLY, SINCE THE START OF
THE NEW LOCATION IS EASILY CALCULATED.

    ╘HIS ALSO MEANS THAT THE ACTUAL
MOVES REQUIRED ONLY A FRACTION OF THE
TIME THAT THE SEARCH REQUIRES WHEN THE
NUMBER OF STRINGS IS FAIRLY LARGE.

    ╘HE LENGTH OF STRINGS HAS VERY
LITTLE EFFECT ON THE TIME REQUIRED FOR
GARBAGE COLLECTION. ╘HE DOMINATING
FACTOR IS THE NUMBER OF STRINGS STORED
ABOVE THE END OF ARRAYS. ╫HEN THE
SEARCH IS MADE, VARIABLES STORED IN
THE CODE ARE PASSED OVER SINCE THEY
ARE NEVER MOVED. ╥UN THE DEMO FOR
EVIDENCE OF THESE STATEMENTS AND READ
THE TEXT SCREENS FOR MORE INFORMATION.


    ╘HAT ABOUT DOES IT FOR THE SUMMARY
OF THE STUDY, SO NOW ╔ WILL CLOSE WITH
SOME COMMENTS AND SOME SUGGESTIONS.

    ╘HIS WHOLE THING WAS PROMPTED BY
╩EFF ╩ONES'S ┬┴╙╔├╙ ARTICLE ON
╠╧┴─╙╘┴╥ #57, AND WHILE A FEW OF HIS
REMARKS MAY NEED TO BE QUALIFIED, HIS
MAIN POINTS ARE WELL PROVED. ┴ FEW
JIFFIES HERE AND THERE ARE OF NO GREAT
IMPORT. ┴ FEW JIFFIES IN EACH PART OF
A 1000 STEP LOOP ARE VERY IMPORTANT.
═ORE TIME IS GAINED BY USING SHORT
CODE AND EFFICIENT ALGORITHMS THAN BY
ATTEMPTING TO CHANGE MULTIPLY TO
DIVIDE OR SOME OTHER SUCH DOUBTFUL
SCHEME. ╫ORRY MORE ABOUT THE BIG
PICTURE.

    ╔ NOW BELIEVE THAT GARBAGE
COLLECTION HAS BEEN BADLY HANDLED IN
THE LITERATURE. ╘HE USUAL THING HAS
BEEN TO MAKE SOME PRONOUNCEMENT
WITHOUT ANY EVIDENCE OR EXPLANATION.
═Y OPINION IS THIS: ╔F THE NUMBER OF
STRINGS STORED AT THE TOP OF MEMORY IS
RELATIVELY SMALL, SAY LESS THAN 60,
SERIOUS PROBLEMS WITH GARBAGE
COLLECTION WILL ONLY ARISE IF
AVAILABLE MEMORY IS SMALL. ╘HE
PROBLEM, THEN, IS TO STRIKE A BALANCE.

    ╔ SUSPECT THERE ARE MANY
TECHNIQUES THAT NEED TO BE EXPLORED
AND DISCUSSED, BUT ╔ AM NOT THE ONE TO
DO IT. ╔ HAD A LOT OF TROUBLE
DESIGNING PROGRAMS TO ILLUSTRATE THE
IDEA. ╘HE MODIFIED ┬┘╘┼╙ #57 DEMO THAT
╔ MENTIONED IN ╨ART ╔ CONTAINED VERY
LONG (ABOUT 140 CHARACTERS) STRINGS
AND WAS CONSTANTLY GENERATING MORE.
┘ET, GARBAGE WAS ONLY COLLECTED AFTER
ABOUT SIX HANDS AND REQUIRED ABOUT
╙┼╓┼╬ ╩╔╞╞╔┼╙.

    ┼MERSON SAID, "╞EAR ALWAYS SPRINGS
FROM IGNORANCE." ├OULD IT BE THAT HE
WAS TALKING ABOUT FEAR OF GARBAGE
COLLECTION?

    ╔T SEEMS OBVIOUS THAT THE SPEED
AND MEMORY USAGE ARE CONNECTED IN MANY
WAYS AND THAT THE TWO MUST BE
CONSIDERED TOGETHER. ╔ LIKE HEAVILY
DOCUMENTED PROGRAMS, AND THIS STUDY
SHOWS THAT SPEED IS NOT SERIOUSLY
AFFECTED BY ╥┼═ STATEMENTS, UNLESS
SPACE IS A PROBLEM.

    ╔N ORDER TO FULLY UNDERSTAND HOW
┬┴╙╔├ USES MEMORY, ONE NEEDS MUCH MORE
DETAIL THAN WAS POSSIBLE HERE.  ╔
STRONGLY SUGGEST THAT SERIOUS
PROGRAMMERS MUST UNDERSTAND THIS AND
SUGGEST THE SOURCES THAT ╔ MENTIONED
IN ╨ART ╔.

    ╬UMBERS AND STRINGS STORED BY
ARRAYS USE LESS SPACE AND ARE MORE
QUICKLY LOCATED THAN THOSE STORED BY
SIMPLE VARIABLES. ╔ BELIEVE THAT IT IS
ONLY A MATTER OF HABIT THAT SO MANY
SIMPLE VARIABLES ARE FOUND IN THE
CODE. ╫ITH A LITTLE ATTITUDE
ADJUSTMENT, WE COULD SEE THIS CHANGE.
╔ CANNOT SEE ANY DIFFICULTY IN
DECLARING ┴╠╠ VARIABLES EARLY IN THE
PROGRAM NOR WITH DECLARING THE MOST
HEAVILY USED SIMPLE VARIABLES NEAR THE
TOP OF THE LIST. ┴ SIMPLE ─╔═
STATEMENT DOES IT ALL. ╘HERE'S NOTHING
WRONG WITH SOMETHING LIKE

100 ─╔═┴$,╔,╩,╦,┬$,├$,┬,├,─,╪,┘,┌

AT THE BEGINNING OF YOUR PROGRAM.

    ═Y EXAMINATION OF CODE HAS SHOWN
THAT SOME PEOPLE DO A GOOD JOB OF
KEEPING THE NUMBER OF VARIABLES SMALL,
WHEREAS OTHERS SEEM TO BE AFRAID TO
REUSE VARIABLES AT ALL. ╔T IS NOT
DIFFICULT TO KNOW WHEN THE VALUE
STORED BY A VARIABLE WILL NOT BE
NEEDED AGAIN, SO THAT THE VARIABLE CAN
BE REUSED.

    ┼VEN THOUGH ╔ SPENT HOURS WAITING
FOR LONG LOOPS TO RUN, HOURS DESIGNING
AND REVISING TESTS, HOURS READING AND
HOURS EVALUATING, THIS STUDY HAS BEEN
GRATIFYING. ╔ BELIEVE THAT ╔ HAVE KEPT
MY OPINIONS TO A MINIMUM AND HAVE
PROVED THOSE THINGS THAT ╔ HAVE
CLAIMED.

    ╔ WISH THAT THOSE WHO READ THIS
COULD LEARN AS MUCH AS ╔ DID. ╔F YOU
WANT TO LEARN SOMETHING, TRY TO FIGURE
OUT HOW TO EXPLAIN IT TO SOMEONE ELSE.

 ═╩


 [─┴╓┼'╙ ┴──┼╬─╒═:] ├OMPUTERS ARE
NECESSARILY LOGICAL. ╨URE REASON AND
SCIENTIFIC METHOD -- AS DISPLAYED BY
═AURICE -- ARE THE ONLY ANSWERS TO
WILD RUMORS AND HALF-TRUTHS. ╘HIS GOES
FOR OPERATING SYSTEM ISSUES AND
VIRUSES! ╚AS [ANYONE] SPENT EVEN A FEW
MOMENTS TRYING TO SCOPE OUT WHY
╫INDOWS HANGS?