╔T WAS AMONGST THE BIRDS WHEN IT ARRIVED ON THE ╨├╪ SOURCE FILES AND OUT OF KINDNESS ╔ LEFT IT THERE SO THAT IT WOULD NOT BE LONELY. ╫HAT EARTHBOUND CREATURE HAS A SKUNK FOR A BEST FRIEND?
┴ND NOW TO THE ARTICLE WHICH ╨ETER ╚UNT OF ╟EO├╠╒┬ ╧┌ KEEPS TELLING ME TO WRITE.
┴T HIS REQUEST ╔ DECIDED TO HAVE A GO AT CONVERTING ╔┬═ ╨├╪ FILES TO ╟EO╨┴╔╬╘ PICTURE IMAGE FILES AND IT HAS TURNED INTO A FAIRLY LONG STORY. ╚OPEFULLY, THE END HAS NOW ARRIVED SO FOR THOSE OF YOU WHO HAVE ALREADY USED A VERSION OF THE ╨├╪/╟EO╨┴╔╬╘ GRAPHICS CONVERTER, WHICH ╔ HAVE BEEN REHASHING FOR THE PAST YEAR OR SO, AND HAVE SEEN STRANGE THINGS OCCURRING, THEN HERE ARE SOME EXPLANATIONS.
╘HE FILES WHICH WERE INCLUDED ON ╟EO├╠╒┬ ┬┴╙╔├ 4 DISK DATED ╧CTOBER 1994 CONTAINED AN ERROR IN THE COMPACTION TO ╟┼╧╙ FORMAT. ╔T DIDN'T HAPPEN TO EVERY CONVERSION BUT TURNED UP ONCE IN A WHILE WHEN A CERTAIN COMBINATION OF DATA WAS READ BY ╟┼╧╙. ╙ORTING OUT THE COMPACTION WAS QUITE A JOB AS THE INFORMATION IN THE ╟┼╧╙ ╨ROGRAMMER'S ╥EF.╟UIDE WAS INCORRECT AND ╔ HAD TO WORK OUT A METHOD ACCEPTABLE TO ╟┼╧╙ BY RECONSTRUCTING HI-RES. PICTURES FROM THE DATA IN EXISTING PICTURE FILES - IF YOU KNOW WHAT ╔ MEAN.
╘HOSE FILES AND THE SUBSEQUENT ╓2.0 WHICH CORRECTED THE COMPACTION ERROR (IT HAS ALREADY BEEN FAIRLY WIDELY CIRCULATED, ORIGINALLY FOR TESTING PURPOSES) ARE NOW FOUND TO PRODUCE FILES WHICH, ALTHOUGH THEY FORM UNBLEMISHED PICTURES, ARE STRICKEN BY WHAT ╔ WILL CALL THE ┌┼╥╧ ┬╒╟. ╔TS EFFECT WAS NOT NOTICED BY ANYONE, APPARENTLY, EXCEPT ╨ETER ═C╟UINN OF ╬EW ┌EALAND AN ENTHUSIASTIC ╟EO├╠╒┬ ╧┌ ART PROVIDER, WHO VERY RECENTLY SENT ME A GRAPHIC ILLUSTRATION OF WHAT WAS HAPPENING TO HIS PICTURES IN ╟EO╨┴╔╬╘ WHEN HE TRIED TO SCROLL BELOW THEM.
╞ROM SQUARE ONE ╔ HAVE TESTED ALL THE CONVERTERS BY VIEWING THE RESULTS WITH ╟EO╓IEW AND ALSO IN ╟EO╨┴╔╬╘ ╓2/├128, WHERE ╔ COULD SCROLL BELOW THE GRAPHIC WITH NO APPARENT PROBLEMS. ╚OWEVER, UPON RECEIPT OF ╨ETER'S LETTER, IT OCCURRED TO ME TO TRY AND ADD FURTHER DATA BELOW THE GRAPHIC. ╘HIS THE DRIVE IGNORED WHEN USING BOTH 'PREVIEW' AND 'UPDATE' OPTIONS AND THE FILE WAS CLOSED WITHOUT BEING ABLE TO ADD ANYTHING TO IT IN THE '┘' DIRECTION.
╔T WAS WHEN ╔ LOADED A ╨├╪ CONVERSION INTO ╟EO╨┴╔╬╘ ╓2/├64 THAT ╔ WAS ABLE TO REPRODUCE ╨ETER'S EXPERIENCES EXACTLY. ╙CROLLING BELOW THE GRAPHIC CAUSED PARTS OF THE GRAPHIC TO 'DOUBLE IMAGE' IN THE AREA BELOW AND THE DRIVE COMPLAINED LOUDLY AS THE PICTURE WAS SCROLLED DOWN AND UP REPEATEDLY. ┴GAIN IT WAS NOT POSSIBLE TO ADD ANY FURTHER DATA TO THE FILE IN THE '┘' DIRECTION EXCEPT THAT ON OCCASION THE 'DOUBLE IMAGING' BECAME A PERMANENT PART OF THE PICTURE.
╔'VE NOW FOUND THE CAUSE OF THE PROBLEM AND IT IS UNDOUBTEDLY ╟┼╧╙ TEACHING ME A LESSON FOR DARING TO TACKLE IT WITH STRAIGHTFOWARD ├╧══╧─╧╥┼ PROGRAMMING INSTEAD OF DOING ALL THINGS VIA ╟EO╨╥╧╟╥┴══┼╥ AND THE DRIVE ROUTINES IT PROVIDES!
═Y APOLOGIES TO ALL FOR ╓2 OF THE CONVERTER WHICH IS ON GEO├╠╒┬ DISK EITHER 334 OR 335. ╓ERSION 3, WHICH WILL PROVIDE CONVERSIONS WITHOUT THE ┌┼╥╧ ┬╒╟ PROBLEM SHOULD ACCOMPANY THIS ARTICLE.
╞OR THOSE WHO ARE IN POSSESSION OF CONVERTED ╨├╪ GRAPHICS AND HAVE BEEN PREVENTED FROM USING THEM FOR PURPOSES OTHER THAN PRINTER DUMPS BY THIS ERROR, THE GOOD NEWS IS THAT A FIX CAN BE EFFECTED QUITE SIMPLY WITH A TRACK AND SECTOR EDITOR.
╞IRST MAKE A COPY OF THE DISK CONCERNED SO THAT ANY EXPERIMENTING THAT COMES TO GRIEF WON'T LEAVE YOU WITHOUT THE ORIGINAL. ╞IND THE NAME OF THE FILE YOU WANT TO FIX WHEREVER IT MAY BE ON TRACK 18 OF THE DISK AND THEN TAKE NOTE OF THE TWO BYTES WHICH APPEAR IN THE HEXADECIMAL POSITIONS $03/$04 IMMEDIATELY BEFORE THE FILE NAME, IF IT IS THE FIRST ONE IN THAT SECTOR. ╞OR THE SECOND FILE THE BYTES ARE AT POSITIONS $23/24, THE THIRD ARE AT $43/44 AND SO ON AT $63/64, $83/84, $┴3/┴4, $├3/├4 OR $┼3/┼4.
╘HESE TWO BYTES ARE THE NUMBERS, PROBABLY IN HEXADECIMAL, OF THE TRACK AND SECTOR OF WHAT ╟┼╧╙ CALLS THE ╔╬─┼╪ ╘┴┬╠┼ FOR THAT PARTICULAR FILE AND IT IS IN THIS TABLE WHERE THE ERROR HAS OCCURRED.
╫HEN CONSULTING THE ╔╬─┼╪ ╘┴┬╠┼ YOU WILL SEE SOMETHING LIKE THIS (IT USUALLY IS IN HEXADECIMAL AND THE PICTURE DATA FOR EACH FILE WILL END AT DIFFERENT SETS OF BYTES):
00: 00 ╞╞ 11 01 11 02 11 07
08: 10 01 10 05 10 08 10 0┴
10: 10 0┼ 09 00 00 00 00 00
╔T IS THOSE TWO FINAL SETS OF ┌┼╥╧'S WHERE THE PROBLEM STARTS. ╘HE ACTUAL PICTURE DATA IN THIS EXAMPLE ENDS AT BYTE $13 WITH $09 00 AND FROM THERE ON UP TO AND INCLUDING BYTE $5┬ ╟┼╧╙ REQUIRES A PADDING OF $00 $╞╞ SO LINE $10 SHOULD BE ALTERED TO READ:
10: 10 0┼ 09 00 00 ╞╞ 00 ╞╞
18: 00 ╞╞ 00 ╞╞ 00 ╞╞ 00 ╞╞
ALL THE WAY TO BYTE $5┬. ╘HE REST OF THE SECTOR SHOULD BE LEFT AS ZEROS.
╘WO THINGS TO WATCH ARE THAT YOU DON'T ACCIDENTLY SUPPOSE THAT THE ZERO AT BYTE $13 (19) ABOVE IS PART OF THE ERROR. ╘HAT PAIR OF BYTES RELATES TO FURTHER FILES AT TRACK NINE ╙┼├╘╧╥ ┌┼╥╧. ╘HE PROBLEM STARTS FROM THE BYTE AT $14 (20). ┴LSO, ALL THE SUBSEQUENT $╞╞'S MUST BE ON THE ODD NUMBERED BYTES OR THE DRIVE WILL ATTEMPT TO FIND A TRACK NUMBERED 255. ╚APPY EDITING!
╔F THAT ISN'T ENOUGH, TESTING TURNED UP A FURTHER PROBLEM - THIS TIME THE FEEDBACK CAME FROM ╟ORDON ╘URRALL, ANOTHER OF ╟EO├╠╒┬ ╧┌'S ART PROVIDERS. ╟ORDON, USING TWO 1571'S, FOUND THAT IN THE COURSE OF CONVERTING HIS ╨├╪ GRAPHICS, PICTURES CONTAINING 'DOUBLE IMAGES' WERE PRODUCED IN THE DESTINATION FILES.
╘HIS WAS A BIT OF A STUMPER AS ╔ HAD USED THIS SYSTEM FOR MOST OF THE CONVERSIONS ╔ DID AND NOTHING LIKE THAT HAPPENED TO ME.
╔ DO HAVE THREE 1571'S, ONE OF WHICH HAS A SWITCH WHICH ALLOWS ME TO USE EITHER THE OLD PRE-1988 ╥╧═ CHIP OR THE NEW ╥╧═ CHIP WHICH THE PREVIOUS OWNER HAD INSTALLED. ╔ DO USE THIS DRIVE CONSTANTLY WITH THE NEW ╥╧═ CHIP SWITCHED IN BUT IN DESPERATION DECIDED TO SEE WHAT WOULD HAPPEN IF ╔ SWITCHED IT OVER TO THE OLD ╥╧═ CHIP. ╫ITHOUT A DOUBT IT WAS THE CAUSE OF 'DOUBLE IMAGING' AS THE CONVERSION PROCESS TOOK PLACE. ╔T WAS QUITE INTERESTING TO WATCH THE DESTINATION DRIVE SPASMODICALLY FAIL TO WRITE A FILE TO THE DISK; IN FACT ╔ WAS ABLE BY COUNTING TO ANTICIPATE JUST WHICH 'PAGES' OF THE ╟┼╧╙ GRAPHIC WOULD BE REPLACED BY THE DATA IN THE PREVIOUS 'PAGE'.
╘HE ODD THING IS THAT IT IS THE DRIVE WITH THE OLD ╥╧═ USED AS THE ╙╧╒╥├┼ WHICH CAUSED THE DISTORTION. ╔T BEHAVED PERFECTLY WHEN USED AS THE DESTINATION DRIVE.
┴PART FROM WHAT THE OLD 1571 ╥╧═ DOES TO THE ╨├╪ CONVERTER WHICH IS, WHEN ALL IS SAID AND DONE, A MINOR PROBLEM, FROM WHAT ╔ AM ABLE TO GLEAN BY LOOKING BACK THROUGH MAGAZINES, IT SEEMS THAT THE OLD ╥╧═ ALSO CAUSES BITS OF ╙┼╤.FILES TO DISAPPEAR WHEN WRITING TO THE SECOND SIDE OF A DISK UNDER CERTAIN CONDITIONS AND THE DRIVE OCCASIONALLY HAS DIFFICULTY IN ACCESSING THE DIRECTORY. ╫ITH ALL THE SECOND HAND EQUIPMENT ON SALE THESE DAYS IT MAY BE JUST AS WELL TO KNOW EXACTLY WHAT ONE HAS.
╘O THIS END THE FOLLOWING SHORT ┬┴╙╔├ PROGRAM WILL PROVIDE THE INFORMATION REQUIRED:
10 ╔╬╨╒╘"─┼╓╔├┼ ╬╒═┬┼╥";─
20 ╧╨┼╬15,─,15
30 ╨╥╔╬╘#15,"═-╥"├╚╥$(0)├╚╥$(192)├╚╥$(1)
40 ╟┼╘#15,┴$
50 ┴=┴╙├(┴$)
60 ╨╥╔╬╘ ┴
70 ├╠╧╙┼15:┼╬─
╔F ┴ WHEN PRINTED =
56, THEN YOU HAVE THE NEW 1571 ╥╧═
66, THEN YOU HAVE THE OLD 1571 ╥╧═
132, THEN YOU ARE USING A ├128─.
╔N CONCLUSION MY THANKS TO ╨ETER ╚UNT FOR HIS INTEREST AND ENCOURAGEMENT DURING MY HASSLES WITH THE CONVERTER AND ALSO TO ╨ETER ═C╟UINN AND ╟ORDON ╘URRALL FOR THE FEEDBACK THEY PROVIDED. ╔T IS INEVITABLE THAT WHEN WRITING A PROGRAM SOME ANGLE DOESN'T GET CHECKED AND ╔ HAVE REALLY APPRECIATED THE DETAILED ERROR REPORTS THAT HAVE BEEN RECEIVED.
═EANWHILE HERE IN ╧┌ WE LOOK FORWARD TO EVERY ISSUE OF GEO╬┼╫╙. ╠ONG MAY IT CONTINUE.
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