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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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Intel 9800758-02 manual Error Simulation, Restarting Program Execution, Error Handling, If line 40 is replaced with

Contents

BASIC-SO Reference Manual A108/0979/7500 FL Preface Page Contents Illustrations Chapter Introduction to BASIC-80 Invoking BASIC-80 Examples Introduction to BASIC-80Basic filename MEMTOPaddress Filename Listing the Directory of a Disk Renaming a FileChanging File Attributes Deleting a File You can now run, list, or edit the program Save LP ,A Commands Statements BASIC-80 Commands Contd BASIC-80 Statements BASIC-80 Statements Contd BASIC-80 Functions BASIC-80 Functions Contd Representing Data Functions Constants Integer ConstantsDecimal Integer Constants Hexadecimal Integer Constants Double-Precision Floating-Point Constants Octal Integer ConstantsSingle-Precision Floating-Point Constants String Constants String VariablesThis is a string constant $ = Enter next data string L4! = Csng l4 YI,1 String Arrays Arithmetic Operators BASIC-SO Operators in Order of Precedence Contd Logical Operators String OperatorNumeric Expressions String Expressions Entering 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*37 Subcommand Command 3D press 3, then D resultsInteger D If AB then If AB then 120 Else Null SET Syntax of the X subcommand is At this point, the other editing subcommands may be used Print Undefined SET The E subcommand is entered Integer C character characterMove the cursor to PRINT. Enter 2C RE L Print Undefined SET. Enter a L Overflow, 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 with Opening a Sequential File Open 1,#1,F1DATES Refer 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 values Closing a Sequential File Value of R$ would be Field #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 record Writing to a Random 1/0 File IntegerSingle-precision value Double-precision value MKI$ Attrib Fdrive numberfilename, W1 Attrib Fdrive numberfilename, WOAuto first lineJ, increment Clear expression,address Commands and Statements Close DEF FNX Rules for function name are the same as for variable name Defsng Defdbl Defstr Defint DIM Delete Error DIREdit END Error expression ExitField FOR-NEXT-STEP GET GosubFor variable=expression to expression Step expression GET I file number ,record number Goto IF-THEN-ELSEInput Kill LETLine Input List LSET, Rset Load Merge NEW Next 9 16 Open On ... GosubOn ... Goto Poke Option BaseOUT String Fields Print UsingPrint Numeric fields If X$=SEVEN and Y$=EIGHT, the results of line 40 would be Prun PUT Randomize Read REM Resume Return Save RUN line numberlstring expression ,FLine number RUN filename 60 END TRON, Troff ? 5,8,2 Wait Width ABS ATN Functions CHR$Cint Csng CVI CVS10 A# = 1.00/3.00 AO/o = Dskf EOF FIX Ok· Inputs HexsINP LEFT$ INTInstr LEN LOCLOF LOG OCT$ MID$MKI$ MKS$ MKD$ Rights Peek expressionPOS integer RIGHT$ string,integer SGN SINSpaces 10 a =1 SPC SPC integerIf A$ = 2 then Print Correct Else Goto SQRexpression TAN 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 Codes Table 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 Codes Table D-2. Ascii Code Definition BEL Appendixe Calling Subroutines Figure B-1. Internal Representation of Numbers and Strings Some Real Examples RESULT=USR%1VARPTRA, VARPTRB, VARPTRC» PRINTA+B+C= Result Figure 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-SO Table F-l. Sample Configuration Jumper Wiring OOOOH-OFFFH Generating Boot-Loaded and PROM-Based Versions BASIC-80 Source FilesBASIC-80 Object Files BASIC-80 Executable Files Generating 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 you ISBC 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 Clock Public Variables Adding User-Written I/O Drivers to RMX/SO BASIC-SO Open 0,#1, L1LlST Figure F-S. Sample User-Written 1/0 Driver Routine Altering BASIC-80 Workspace Burning a BASIC-80 Program Into Prom Baprom F1HEATER.BAS Page Index Ase BASIC-80 RIGHT$,7-1O Request for Readerscomments 111111