Intel 9800758-02 Logical Operators, String Operator, Numeric Expressions, String Expressions

Page 22

Language Elements

BASIC-SO

Logical Operators

The logical operators NOT, AND, OR, XOR, IMP, and EQV are operators that compare the nth bit of argument X with the nth bit of argument Y. They are evaluated after the arithmetic and relational operators; therefore, arithmetic expres- sions resolve to a number which is compared with another number. A relational operator test can be used with logical operations. If there are two logical operators of the same precedence in a single expression, they are evaluated left to right. Table 2-6 lists the logical operators in order of precedence'. Some examples of the logical operators, used in complex expressions, are shown below.

IF A>=3.5X OR X > 3 THEN 01=0

IF B=1 OR B=2 OR B=3 THEN 2750 ELSE 280u

IF (A-B) AND (B+3) THEN STOP ELSE IF (A AND B) THEN CLOSE 2

String Operator

The relational operators may be used with strings to compare them according to ASCII order. If strings of unequal length are compared, and the shorter is identical to the first part of the longer, then the longer is greater. There is one operator only used with strings: the concatenation operator (+). This operator defines a string as two or more strings joined together.

A$ = B$+C$

Expressions

Except for the command and stateqlent instructions, all of the language elements previously discussed can be combined to form expressions. Depending on the type of constants, variables, and operators used, expressions can be classed as numeric or string.

Numeric Expressions

In BASIC-80, numeric expressions are created with numeric variables, constants, functions, and operators. Variables are initialized with 0, and may be assigned other values with assignment statements, or with INPUT statements during program execution.

Any function which returns a numeric value can be used in a numeric expression. Strings can only be used if they are converted to a number. Numeric expressions can use arithmetic, logical, or relational operators. Some numeric expressions:

K(I) = B*SOR(X)

IF A>12.1 THEN C = C + 1

IF PEEK (2FFFH) AND OCH THEN PRINT "ON"

String Expressions

String expressions can be specified in BASIC-80 using string constants, string variables, relational operators, and the concatenation operator (+). The concatena- tion operator combines two strings into one. If the resulting string is longer than 255 characters, execution halts and an error message is displayed. Some string expres- sions are:

A$ = "NAME:" + NAME$

IF B1$>R$ THEN 81$ = ""

R$(I)=R$(I) + S$(I) + "DONE"

2-12

Page 21 Page 23
Image 22
Page 21 Page 23
Contents BASIC-SO Reference Manual A108/0979/7500 FL Preface Page Contents Illustrations Chapter Introduction to BASIC-80 Invoking BASIC-80Basic filename MEMTOPaddress ExamplesIntroduction to BASIC-80 FilenameChanging File Attributes Listing the Directory of a DiskRenaming a File 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 FunctionsDecimal Integer Constants ConstantsInteger Constants Hexadecimal Integer ConstantsSingle-Precision Floating-Point Constants Octal Integer ConstantsDouble-Precision Floating-Point Constants This is a string constant String ConstantsString Variables $ = Enter next data stringL4! = Csng l4 YI,1String Arrays Arithmetic Operators BASIC-SO Operators in Order of Precedence ContdNumeric Expressions Logical OperatorsString Operator String ExpressionsEntering and Editing Programs 30 A=8*52 30 A=8*37 30 A=8*5230 A=8 30 A--=8xx*522537 Control-R a = 8*37Integer D SubcommandCommand 3D press 3, then D results If AB thenIf AB then 120 Else Null SET Syntax of the X subcommand is At this point, the other editing subcommands may be usedMove the cursor to PRINT. Enter 2C RE L Print Undefined SET The E subcommand is enteredInteger C character character Print Undefined SET. Enter a LSyntax Error Messages BASIC-80 Error MessagesOverflow, Underflow, and Divide-by-Zero Error Trapping Trace Facility Restarting Program Execution Error SimulationError Handling If line 40 is replaced withOpening a Sequential File Open 1,#1,F1DATESReading from a Sequential File Refer to for further details of Print UsingWriting to a Sequential File If executed four times, it would read all eight valuesClosing a Sequential File Value of R$ would beDefining a Random 1/0 Field-FIELD BuffersField #3, 20 AS N$ Disk File Input/Output Field #3, 20 AS N$, 9 AS SS$Any of the parameters can be variables Opening and Closing a Random Disk FileReading from a Random 1/0 File To read the next recordSingle-precision value Writing to a Random 1/0 FileInteger Double-precision valueMKI$ Auto first lineJ, increment Attrib Fdrive numberfilename, W1Attrib Fdrive numberfilename, WO Clear expression,addressCommands and Statements CloseDEF FNX Rules for function name are the same as for variable nameDefsng Defdbl Defstr Defint DIM DeleteEdit ErrorDIR ENDField Error expressionExit FOR-NEXT-STEPFor variable=expression to expression Step expression GETGosub GET I file number ,record numberInput IF-THEN-ELSEGoto Line Input KillLET ListLSET, Rset LoadMerge NEWNext 9 16On ... Goto On ... GosubOpen OUT Option BasePoke Print Print UsingString Fields Numeric fields If X$=SEVEN and Y$=EIGHT, the results of line 40 would bePrun PUTRandomize ReadREM Resume ReturnLine number RUN filename SaveRUN line numberlstring expression ,F 60 ENDTRON, Troff ? 5,8,2Wait WidthABS ATNCint CHR$Functions 10 A# = 1.00/3.00 CsngCVI CVS AO/o =Dskf EOFFIX Ok·INP HexsInputs Instr INTLEFT$ LOF LENLOC LOGMKI$ MKS$ MKD$ MID$OCT$ POS integer RightsPeek expression RIGHT$ string,integerSpaces SGNSIN 10 a =1If A$ = 2 then Print Correct Else Goto SPCSPC integer SQRexpressionTAB expression STR$ expressionTAN 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 tab across the line To halt program execution and return to commandLevel 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-OFFFHBASIC-80 Object Files Generating Boot-Loaded and PROM-Based VersionsBASIC-80 Source Files BASIC-80 Executable FilesGenerating a Boot-Loaded RMX/80 BASIC-80 Setting baud rates, refer to the RMX/SO Users Guide That are not boot loadedThis option is used to allocate memory. It is 1 if the boot 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 Configuration Requirements Configuring DFS on an iSBC 80/10Adding BASIC-SO to an Existing RMX/SO Configuration 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
Top Page Image Contents