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EXTENDED BASIC UNRAVELLED IIAPPENDIX FBASIC/EXTENDED ERROR ENTRY POINTSORIGIN:SPECTRAL ASSOCREVISED:12/26/1999 WALTER K ZYDHEKThere are times when it is useful to cause an error message to beprinted to the screen in the same manner that BASIC prints its errormessages. The following table is provided to give the user the DISKBASIC entry points which will cause error messages to be printed tothe screen. A JMP to one of these error message routines will causethe two letter short form error message to be printed on the screenand a pseudo—warm start into BASIC will be taken. The pseudo—warmstart will reset the stack, the string stack and the continue pointerand jump to BASIC’s direct mode (OK).BASIC/EXTENDED ERROR JUMPSNAME NBR LABEL ADDR DESCRIPTIONNF 00 LB108 B108 NEXT WITHOUT FORSN 01 LB277 B277 SYNTAX ERRORRG 02 LAECF AECF RETURN WITHOUT GOSUBOD 03 LB0C3 B0C3 COND OUT OF DATAFC 04 LB44A B44A ILLEGAL FUNCTION CALLOV 05 LBA92 BA92 OVERFLOWOM 06 LAC44 AC44 OUT OF MEMORYUL 07 LAED2 AED2 UNDEFINED LINE NUMBERBS 08 LB447 B447 BAD SUBSCRIPTDD 09 LB43B B43B COND REDIMENSIONED ARRAY/0 10 LBC06 BC06 DIVISION BY ZEROID 11 INPUT AFF5 COND ILLEGAL DIRECT STATEMENTTM 12 LB151 B151 TYPE MISMATCHOS 13 LB585 B585 COND OUT OF STRING SPACELS 14 LB625 B625 STRING TOO LONGST 15 LB553 B553 STRING FORMULA TOO COMPLEXCN 16 LAE32 AE32 COND CAN'T CONTINUEFD 17 LAFD6 AFD6 COND BAD FILE DATAAO 18 LA61C A61C FILE ALREADY OPENDN 19 LA61F A61F DEVICE NUMBER ERRORIO 20 LA619 A619 INPUT/OUTPUT ERRORFM 21 LA616 A616 BAD FILE MODENO 22 LA3FB A3FB FILE NOT OPENIE 23 LB03F B03F COND INPUT PAST END OF FILEDS 24 LAC94 AC94 COND DIRECT STATEMENT IN FILEUF 25 L88BF 88BF COND UNDEFINED FUNCTION CALLNE 26 L8CDD 8CDD FILE NOT FOUNDThe addresses given for the entry points are valid for COLORBASIC Versions 1.0, 1.1, 1.2 and Extended BASIC Versions 1.0, 1.1, and 2.0.If the address is followed by a COND, the corresponding entry point is notunconditional, meaning that ACCB will be loaded with the error but somesort of test will be imposed before program control will be passed to theerror handler. As required, these conditional errors may be generated byloading a value equal to 2*(error number) into ACCB and then JMPing to$AC46.F1
EXTENDED BASIC UNRAVELLED IIAPPENDIX GEXTENDED BASIC 1.0 DIFFERENCESORIGIN:SPECTRAL ASSOCREVISED:12/26/1999 WALTER K ZYDHEKThe differences between Extended Basic 1.0 and 1.1 are not earthshaking.The primary difference involves the bug in the PCLEAR commandwhich caused BASIC programs to generate a syntax or illegal functioncall error at certain times when a PCLEAR command was executed ina BASIC program. This error was caused by the fact that the BASIC inputpointer was not adjusted when the program was moved as a result of aPCLEAR command. Accordingly, when control was returned to the BASICprogram after a PCLEAR command the BASIC input pointer would invariablyend up pointing to the middle of the program which would causethe error.ADDRESS80D0-80DDDIFFERENCES BETWEEN EXTENDED BASIC 1.0 AND 1.1Patch to move the BASIC input pointer during PCLEAR(see Figure G1). The originial code in the 1.0 versionwas designed to allow the SAM chip to be programmedfor 64K RAMs on power up but the code was never accessedby any routines in any of the 3 Basic ROMs.* THIS CODE IS NOT USED BY ANY OF THE BASICS80D0 B6 FF22 LDA PIA1+2 READ PIA PORT B80D3 85 02 BITA #2 CHECK MEM SIZE JUMPER80D5 26 03 BNE L80DA BRANCH IF HIGH80D7 B7 FFDD STA SAM+29 SET SAM CNTL REG MEM SIZE TO 64K80DA 6E 84 L80DA JMP ,X JUMP TO ADDRESS IN X REG80DC 00 00 FCB $00,$00 DEAD SPACEFigure G1 - Version 1.0 Code80FF Change version number 1.0/1.18112 Change Copyright Year (units digit)8C1B-8C22Patch to fix the DLOAD bug (see Figure G2). The codein 1.0 version did not allow for the fact that thecurrent BASIC input character was not in ACCA followingthe CLOSEing of cassette files (JSR LA429).8C1B 6F E2 CLR ,-S SAVE DEFAULT TOKEN (NON DLOADM) ON STACK8C1D 81 4D CMPA #'M' IS IT DLOADM?8C1F 26 04 BNE L8C25 NO8C21 A7 E4 STA ,S SAVE THE M ON THE STACKFigure G2 - Version 1.0 code8C51Change instruction op code from BNE(1.0) to BEQ(1.1).This change was necessitated by the previous fix toDLOAD.9179 Change op code address field from #12(1.0) to #10(1.1).This change and the one following fix a minor bug inG1
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TABLE OF CONTENTS1 FOREWORD……
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EXTENDED BASIC UNRAVELLED II INTROD
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