Intel 9800758-02 manual Error Simulation, Restarting Program Execution, Error Handling

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Error Handling

BASIC-SO

Error Simulation

BASIC-SO provides a statement that can simulate any errors which produce an error code. When the ERROR statement is encountered during program execution, BASIC-SO acts as if the specified error had occurred. The example below demonstrates how ERROR can be used to test an error handling routine.

10ON ERROR GOTO 70

20INPUT A

30B = A* .3842

40PRINT B

50GOTO 20

70IF 11 = ERR THEN PRINT "Division by zero"

80RESUME NEXT

If line 40 is replaced with:

40 ERROR 11

Program control transfers to line 70 regardless of the result of the operation in line 30.

Restarting Program Execution

You can restart program execution after it has halted with the RUN or CONT instruction, and after an error in an ON ERROR routine with the RESUME instruction. Remember that RUN sets all variables to zero.

RUN restarts program execution at the lowest-numbered line of a program if no line number is specified, or at the specified line number. It can be used at any time.

CONT restarts execution at the line after a STOP, END, or CONTROL-C is en- countered. CONT will also restart program execution after an error, but it will try to execute the erroneous line.

RESUME can only be used when the halt occurs in an ON ERROR routine. It is given following the error-resolving routine pointed to by the ON ERROR instruc- tion. It can be used three ways: RESUME to begin execution at the erroneous line; RESUME NEXT to begin execution at the line following the erroneous line; RESUME followed by a line number to begin execution at any other line.

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Contents BASIC-SO Reference Manual A108/0979/7500 FL Preface Page Contents Illustrations Chapter Introduction to BASIC-80 Invoking BASIC-80Examples Introduction to BASIC-80Basic filename MEMTOPaddress FilenameListing the Directory of a Disk Renaming a FileChanging File Attributes Deleting a FileYou can now run, list, or edit the program Save LP ,ACommands StatementsBASIC-80 Commands Contd BASIC-80 StatementsBASIC-80 Statements Contd BASIC-80 FunctionsBASIC-80 Functions Contd Representing Data FunctionsConstants Integer ConstantsDecimal Integer Constants Hexadecimal Integer ConstantsDouble-Precision Floating-Point Constants Octal Integer ConstantsSingle-Precision Floating-Point Constants String Constants String VariablesThis is a string constant $ = Enter next data stringL4! = Csng l4 YI,1String Arrays Arithmetic Operators BASIC-SO Operators in Order of Precedence ContdLogical Operators String OperatorNumeric Expressions String ExpressionsEntering and Editing Programs 30 A=8*52 30 A=830 A=8*52 30 A=8*37 30 A--=8xx*522537 Control-R a = 8*37Subcommand Command 3D press 3, then D resultsInteger D If AB thenIf AB then 120 Else Null SET Syntax of the X subcommand is At this point, the other editing subcommands may be usedPrint Undefined SET The E subcommand is entered Integer C character characterMove the cursor to PRINT. Enter 2C RE L Print Undefined SET. Enter a LOverflow, Underflow, and Divide-by-Zero BASIC-80 Error MessagesSyntax Error Messages Error Trapping Trace Facility Error Simulation Error HandlingRestarting Program Execution If line 40 is replaced withOpening a Sequential File Open 1,#1,F1DATESRefer to for further details of Print Using Writing to a Sequential FileReading from a Sequential File If executed four times, it would read all eight valuesClosing a Sequential File Value of R$ would beField #3, 20 AS N$ BuffersDefining a Random 1/0 Field-FIELD Disk File Input/Output Field #3, 20 AS N$, 9 AS SS$Opening and Closing a Random Disk File Reading from a Random 1/0 FileAny of the parameters can be variables To read the next recordWriting to a Random 1/0 File IntegerSingle-precision value Double-precision valueMKI$ Attrib Fdrive numberfilename, W1 Attrib Fdrive numberfilename, WOAuto first lineJ, increment Clear expression,addressCommands and Statements CloseDEF FNX Rules for function name are the same as for variable nameDefsng Defdbl Defstr Defint DIM DeleteError DIREdit ENDError expression ExitField FOR-NEXT-STEPGET GosubFor variable=expression to expression Step expression GET I file number ,record numberGoto IF-THEN-ELSEInput Kill LETLine Input ListLSET, Rset LoadMerge NEWNext 9 16Open On ... GosubOn ... Goto Poke Option BaseOUT String Fields Print UsingPrint Numeric fields If X$=SEVEN and Y$=EIGHT, the results of line 40 would bePrun PUTRandomize ReadREM Resume ReturnSave RUN line numberlstring expression ,FLine number RUN filename 60 ENDTRON, Troff ? 5,8,2Wait WidthABS ATNFunctions CHR$Cint Csng CVI CVS10 A# = 1.00/3.00 AO/o =Dskf EOFFIX Ok·Inputs HexsINP LEFT$ INTInstr LEN LOCLOF LOGOCT$ MID$MKI$ MKS$ MKD$ Rights Peek expressionPOS integer RIGHT$ string,integerSGN SINSpaces 10 a =1SPC SPC integerIf A$ = 2 then Print Correct Else Goto SQRexpressionTAN expression STR$ expressionTAB expression Here is an example of how the USRn statement is used 60 AO/o =Appendix a BASIC-SO Error Codes Table A-I. BASIC-80 Error CodesTable A-I. BASIC-SO Error Codes Contd Appendix B BASIC-SO Reserved Words Page To halt program execution and return to command LevelTo tab across the line To resume program execution after it is stopped byPage Table D-l. Ascii Code List Appendix D Ascii CodesTable D-2. Ascii Code Definition BELAppendixe Calling Subroutines Figure B-1. Internal Representation of Numbers and Strings Some Real Examples RESULT=USR%1VARPTRA, VARPTRB, VARPTRC» PRINTA+B+C= ResultFigure E-2 /8085 Assembly Language Program Figure E-3. PL/M-80 Program Appendix F RMX/SO BASIC-SO Initializing the Predefined RMX/SO BASIC-SO Configuration ISIS-II BASIC-SOTable F-l. Sample Configuration Jumper Wiring OOOOH-OFFFHGenerating Boot-Loaded and PROM-Based Versions BASIC-80 Source FilesBASIC-80 Object Files BASIC-80 Executable FilesGenerating a Boot-Loaded RMX/80 BASIC-80 That are not boot loaded This option is used to allocate memory. It is 1 if the bootSetting baud rates, refer to the RMX/SO Users Guide This option enables your user-written I/O drivers if youISBC 80/20-4 Generating a PROM-Based RMX/80 BASIC-80 Prom F1 RMX820.L1BSTART, & FOBASCM.OBJ,& FORMXBAS.LlB F1 DFSDIR. L1BDIRECTORY ,RENAM E,& F1 MTI810.L1B Configuring DFS on an iSBC 80/10 Adding BASIC-SO to an Existing RMX/SO ConfigurationConfiguration Requirements ISBC SO/10 System ClockPublic Variables Adding User-Written I/O Drivers to RMX/SO BASIC-SO Open 0,#1, L1LlSTFigure F-S. Sample User-Written 1/0 Driver Routine Altering BASIC-80 Workspace Burning a BASIC-80 Program Into PromBaprom F1HEATER.BAS Page Index Ase BASIC-80 RIGHT$,7-1O Request for Readerscomments 111111