bwBASIC(1)

NAME
bwBASIC - BASIC Interpreter/Shell, version 2.10

SYNOPSIS
The Bywater BASIC Interpreter (bwBASIC) implements a large superset of the ANSI Standard for Minimal BASIC (X3.60-1978) and a significant subset of the ANSI Standard for Full BASIC (X3.113-1987) in C. It also offers shell programming facilities as an extension of BASIC. bwBASIC seeks to be as portable as possible. bwBASIC can be configured to emulate features, commands, and functions available on different types of BASIC interpreters; see the file INSTALL for further installation information. The interpreter is fairly slow. Whenever faced with a choice between conceptual clarity and speed, I have consistently chosen the former. The interpreter is the simplest design available, and utilizes no system of intermediate code, which would speed up considerably its operation. As it is, each line is interpreted afresh as the interpreter comes to it. bwBASIC implements one feature not available in previous BASIC interpreters: a shell command can be entered interactively at the bwBASIC prompt, and the interpreter will execute it under a command shell. For instance, the command "dir *.bas" can be entered in bwBASIC (under DOS, or "ls -l *.bas" under UNIX) and it will be executed as from the operating system command line. Shell commands can also be given on numbered lines in a bwBASIC program, so that bwBASIC can be used as a shell programming language. bwBASIC's implementation of the RMDIR, CHDIR, MKDIR, NAME, KILL, ENVIRON, and ENVIRON$() commands and functions offer further shell-processing capabilities.

TERMS OF USE
This version of Bywater BASIC is released under the terms of the GNU General Public License (GPL), which is distributed with this software in the file "COPYING". The GPL specifies the terms under which users may copy and use the software in this distribution. A separate license is available for commercial distribution, for information on which you should contact the author.

QUICK REFERENCE LIST OF COMMANDS AND FUNCTIONS
Be aware that many of these commands and functions will not be available unless you have set certain flags in the header files (see the expanded reference section below for dependencies). ABS( number ) ASC( string$ ) ATN( number ) CALL subroutine-name CASE ELSE | IF partial-expression | constant CHAIN [MERGE] file-name [, line-number] [, ALL] CHDIR pathname CHR$( number ) CINT( number ) CLEAR CLOSE [[#]file-number]... CLS COMMON variable [, variable...] COS( number ) CSNG( number ) CVD( string$ ) CVI( string$ ) CVS( string$ ) DATA constant[,constant]... DATE$ DEF FNname(arg...)] = expression DEFDBL letter[-letter](, letter[-letter])... DEFINT letter[-letter](, letter[-letter])... DEFSNG letter[-letter](, letter[-letter])... DEFSTR letter[-letter](, letter[-letter])... DELETE line[-line] DIM variable(elements...)[variable(elements...)]... DO NUM|UNNUM DO [WHILE expression] EDIT ELSE ELSEIF END IF | FUNCTION | SELECT | SUB ENVIRON variable-string = string ENVIRON$( variable-string ) EOF( device-number ) ERASE variable[, variable]... ERL ERR ERROR number EXP( number ) FIELD [#] device-number, number AS string-variable [, number AS string-variable...] FILES filespec$ FUNCTION FOR counter = start TO finish [STEP increment] GET [#] device-number [, record-number] GOSUB line | label GOTO line | label HEX$( number ) IF expression THEN [statement [ELSE statement]] INKEY$ INPUT [# device-number]|[;]["prompt string";]list of variables INSTR( [start-position,] string-searched$, string-pattern$ ) INT( number ) KILL file-name LEFT$( string$, number-of-spaces ) LEN( string$ ) LET variable = expression LINE INPUT [[#] device-number,]["prompt string";] string-variable$ LIST line[-line] LOAD file-name LOC( device-number ) LOCATE line, column LOF( device-number ) LOG( number ) LOOP [UNTIL expression] LSET string-variable$ = expression MERGE file-name MID$( string$, start-position-in-string[, number-of-spaces ] ) MKD$( number ) MKDIR pathname MKI$( number ) MKS$( number ) NAME old-file-name AS new-file-name NEW NEXT [counter] OCT$( number ) ON variable GOTO|GOSUB line[,line,line,...] ON ERROR GOSUB line OPEN "O"|"I"|"R", [#]device-number, file-name [,record length] file-name FOR INPUT|OUTPUT|APPEND AS [#]device-number [LEN = record-length] OPTION BASE number POS PRINT [# device-number,][USING format-string$;] expressions... PUT [#] device-number [, record-number] QUIT RANDOMIZE number READ variable[, variable]... REM string RESTORE line RETURN RIGHT$( string$, number-of-spaces ) RMDIR pathname RND( number ) RSET string-variable$ = expression RUN [line][file-name] SAVE file-name SELECT CASE expression SGN( number ) SIN( number ) SPACE$( number ) SPC( number ) SQR( number ) STOP STR$( number ) STRING$( number, ascii-value|string$ ) SUB subroutine-name SWAP variable, variable SYSTEM TAB( number ) TAN( number ) TIME$ TIMER TROFF TRON VAL( string$ ) WEND WHILE expression WIDTH [# device-number,] number WRITE [# device-number,] element [, element ]....

GENERAL NOTES ON USAGE
4.a. Interactive Environment An interactive environment is provided if the flag INTERACTIVE is defined as TRUE in bwbasic.h, so that a line with a line number can be entered at the bwBASIC prompt and it will be added to the program in memory. Line numbers are not strictly required, but are useful if the interactive enviroment is used for programming. For longer program entry one might prefer to use an ASCII text editor, and in this case lines can be entered without numbers. One can use DO NUM and DO UNNUM to number or unnumber lines. See also the documentation below for the pseudo-command EDIT. 4.b. Naming Conventions Command names and function names are not case sensitive, so that "Run" and "RUN" and "run" are equivalent and "abs()" and "ABS()" and "Abs()" are equivalent. HOWEVER, variable names ARE case sensitive in bwbASIC, so that "d$" and "D$" are different variables. This differs from some BASIC implementations where variable names are not case sensitive. Variable names can use any alphabetic characters, the period and underscore characters and decimal digits (but not in the first position). They can be terminated with '#' or '!' to allow Microsoft-type names, even though the precision is irrelevant to bwBASIC. 4.c. Numerical Constants Numerical constants may begin with a digit 0-9 (decimal), with the "&H" or "&h" (hexadecimal) or the "&o" or "&O" (octal). Decimal numbers may terminated with 'E', 'e', 'D', or 'd' followed by an exponent number to denote exponential notation. Decimal constants may also be terminated by the '#' or '!' to comply with Microsoft-style precision terminators, although the precision specified will be irrelevant to bwBASIC. 4.d. Command-Line Execution A filename can be specified on the command line and will be LOADed and RUN immediately, so that the command line bwbasic prog.bas will load and execute "prog.bas". 4.e. Program Storage All programs are stored as ASCII text files. 4.f. TRUE and FALSE TRUE is defined as -1 and FALSE is defined as 0 in the default distribution of bwBASIC. These definitions can be changed by those compiling bwBASIC (see file BWBASIC.H). 4.g. Assignments Assignment must be made to variables. This differs from some implementations of BASIC where assignment can be made to a function. Implication: "INSTR( 3, x$, y$ ) = z$" will not work under bwBASIC. 4.h. Operators and Precedence bwBASIC recognizes the following operators, with their level of precedence given (1 = highest): ^ 1 exponentiation * 2 multiplication / 2 division 3 integer division + 5 addition - 5 subtraction = 6 equality or assignment MOD 4 modulus (remainder) arithmetic <> 7 inequality < 8 less than > 9 greater than <= 10 less than or equal to =< 10 less than or equal to >= 11 greater than or equal to => 11 greater than or equal to NOT 12 negation AND 13 conjunction OR 14 disjunction XOR 15 exclusive or IMP 16 implication EQV 17 equivalence 4.h. Numerical Precision (NOT) bwBASIC utilizes numbers with only one level of precision. If the flag NUMBER_DOUBLE is defined as TRUE in bwbasic.h, the precision implemented will be that of the C "double" data type; otherwise (default) the precision will be that of the C "float" type. At a number of points there are commands (or pseudo- commands) that seem to recognize Microsoft-style precision distinctions, but for the most part these are just work-around aliases to allow Microsoft-style programs to be run.

EXPANDED REFERENCE FOR COMMANDS AND FUNCTIONS
The "Dependencies" listed in the folowing reference materials refers to flags that must be set to TRUE in bwbasic.h for the associated command or function to be implemented. These flags are as follows: (core) Commands and Functions in any implementation of bwBASIC; these are the ANSI Minimal BASIC core INTERACTIVE Commands supporting the interactive programming environment COMMON_CMDS Commands beyond ANSI Minimal BASIC which are common to Full ANSI BASIC and Microsoft BASICs COMMON_FUNCS Functions beyond the ANSI Mimimal BASIC core, but common to both ANSI Full BASIC and Microsoft-style BASIC varieties UNIX_CMDS Commands which require Unix-style directory and environment routines not specified in C STRUCT_CMDS Commands related to structured programming; all of these are part of the Full ANSI BASIC standard ANSI_FUNCS Functions unique to ANSI Full BASIC MS_CMDS Commands unique to Microsoft BASICs MS_FUNCS Functions unique to Microsoft BASICs ------------------------------------------ Function: ABS( number ) Description: ABS returns the absolute value of the argument 'number'. Dependencies: (core) ------------------------------------------ Function: ASC( string$ ) Description: ASC returns the ASCII code for the first letter in the argument string$. Dependencies: MS_FUNCS ------------------------------------------ Function: ATN( number ) Description: ATN returns the arctangent value of the argument 'number' in radians. Dependencies: (core) ------------------------------------------ Command: CALL subroutine-name Description: CALL calls a named subroutine (see SUB and END SUB). Dependencies: STRUCT_CMDS ------------------------------------------ Command: CASE ELSE | IF partial-expression | constant Description: CASE introduces an element of a SELECT CASE statement (see SELECT CASE). CASE IF introduces a conditional SELECT CASE element, and CASE ELSE introduces a default SELECT CASE element. Dependencies: STRUCT_CMDS ------------------------------------------ Command: CHAIN [MERGE] file-name [, line-number] [, ALL] Description: CHAIN passes control to another BASIC program. Variables declared COMMON (q.v.) will be passed to the new program. Dependencies: COMMON_CMDS ------------------------------------------ Command: CHDIR pathname$ Description: CHDIR changes the current directory to that indicated by the argument pathname$. Dependencies: UNIX_CMDS ------------------------------------------ Function: CHR$( number ) Description: CHR$ returns a one-character string with the character corresponding to the ASCII code indicated by argument 'number'. Dependencies: COMMON_FUNCS ------------------------------------------ Function: CINT( number ) Description: CINT returns the truncated integer for the argument 'number'. Dependencies: MS_FUNCS ------------------------------------------ Command: CLEAR Description: CLEAR sets all numerical variables to 0, and all string variables to null. Dependencies: COMMON_CMDS ------------------------------------------ Command: CLOSE [[#]file-number]... Description: CLOSE closes the file indicated by file-number (see OPEN). Dependencies: COMMON_CMDS ------------------------------------------ Command: CLS Description: CLS clears the display screen (IBM and compatibles only as of version 2.10). Dependencies: IMP_IQC and IMP_CMDLOC ------------------------------------------ Command: CMDS Description: CMDS is a debugging command that prints a list of all implemented bwBASIC commands. Dependencies: DEBUG ------------------------------------------ Command: COMMON variable [, variable...] Description: COMMON designates variables to be passed to a CHAINed program (see CHAIN). Dependencies: COMMON_CMDS ------------------------------------------ Function: COS( number ) Description: COS returns the cosine of the argument 'number' in radians. Dependencies: (core) ------------------------------------------ Function: CSNG( number ) Description: CSNG is a pseudo-function that has no effect under bwBASIC. It replicates a Microsoft-type command that would convert the 'number' to single-precision. Dependencies: MS_FUNCS ------------------------------------------ Function: CVD( string$ ) Description: CVD converts the argument string$ into a bwBASIC number (precision is irrelevant in bwBASIC since bwBASIC numbers have only one precision). Implenentation-Specific Notes: CVD(), CVI(), CVS(), MKI$(), MKD$(), MKS$(): These functions are implemented, but are dependent on a) the sizes for integer, float, and double values on particular systems, and b) how particular versions of C store these numerical values. The implication is that data files created using these functions on a DOS-based microcomputer may not be translated correctly by bwBASIC running on a Unix-based computer. Similarly, data files created by bwBASIC compiled by one version of C may not be readable by bwBASIC compiled by another version of C (even under the same operating system). So be careful with these. Dependencies: MS_FUNCS ------------------------------------------ Function: CVI( string$ ) Description: CVI converts the argument string$ into a bwBASIC number (precision is irrelevant in bwBASIC since bwBASIC numbers have only one precision; see also the note on CVD). Dependencies: MS_FUNCS ------------------------------------------ Function: CVS( string$ ) Description: CVI converts the argument string$ into a bwBASIC number (precision is irrelevant in bwBASIC since bwBASIC numbers have only one precision; see also the note on CVD). Dependencies: MS_FUNCS ------------------------------------------ Command: DATA constant[,constant]... Description: DATA stores numerical and string constants to be accessed by READ (q.v.). Dependencies: (core) ------------------------------------------ Function: DATE$ Description: DATE$ returns the current date based on the computer's internal clock as a string in the form "YYYY-MM-DD". As implemented under bwBASIC, DATE$ cannot be used for assignment (i.e., to set the system date). Note: bwBASIC presently (v2.10) does not allow assignment to a function. Dependencies: COMMON_FUNCS ------------------------------------------ Command: DEF FNname(arg...)] = expression Description: DEF defines a user-written function. This function corresponds to Microsoft-type implementation, although in bwBASIC DEF is a working equivalent of FUNCTION. Dependencies: (core) ------------------------------------------ Command: DEFDBL letter[-letter](, letter[-letter])... Description: DEFDBL declares variables with single-letter names as numerical variables (precision is irrelevant in bwBASIC). Dependencies: MS_CMDS ------------------------------------------ Command: DEFINT letter[-letter](, letter[-letter])... Description: DEFINT declares variables with single-letter names as numerical variables (precision is irrelevant in bwBASIC). Dependencies: MS_CMDS ------------------------------------------ Command: DEFSNG letter[-letter](, letter[-letter])... Description: DEFSNG declares variables with single-letter names as numerical variables (precision is irrelevant in bwBASIC). Dependencies: MS_CMDS ------------------------------------------ Command: DEFSTR letter[-letter](, letter[-letter])... Description: DEFSTR declares variables with single-letter names as string variables. Dependencies: MS_CMDS ------------------------------------------ Command: DELETE line[-line] Description: DELETE deletes program lines indicated by the argument(s). If you want to use DELETE for non- numbered programs, first use DO NUM, then DELETE, then DO UNNUM. Dependencies: INTERACTIVE ------------------------------------------ Command: DIM variable(elements...)[variable(elements...)]... Description: DIM specifies variables that have more than one element in a single dimension, i.e., arrayed variables. Note: As implemented under bwBASIC, DIM accepts only parentheses as delimiters for variable fields. (Some BASICs allow the use of square brackets.) Dependencies: (core) ------------------------------------------ Command: DO NUM|UNNUM Description: DO NUM numbers all lines in a program. The first line is given the number 10, and subsequent lines are numbered consecutively in multiples of 10. DO UNNUM removes all line numbers from a program. NOTE that these functions do nothing to line numbers, e.g., following a GOSUB or GOTO statement; these commands cannot be used as a replacement for RENUM (available in some systems, but not bwBASIC). With these commands, however, one can develop unnumbered programs by entering new lines with numbers, then running DO UNNUM to remove the line numbers. Together with LOAD and SAVE (q.v.) one can use bwBASIC as a primitive text editor. Dependencies: INTERACTIVE ------------------------------------------ Command: DO [WHILE expression] Description: DO implements a number of forms of program loops. DO...LOOP simply loops; the only way out is by EXIT; DO WHILE...LOOP loops while "expression" is true (this is equivalent to the older WHILE-WEND loop, also implemented in bwBASIC); DO...LOOP UNTIL loops until the expression following UNTIL is true. Dependencies: STRUCT_CMDS ------------------------------------------ Command: EDIT Description: EDIT is a pseudo-command which calls the text editor specified in the variable BWB.EDITOR$ to edit the program in memory. After the call to the text editor, the (edited) prgram is reloaded into memory. The user normally must specific a valid path and filename in BWB.EDITOR$ before this command will be useful. Dependencies: COMMON_CMDS ------------------------------------------ Command: ELSE Description: ELSE introduces a default condition in a multi-line IF statement. Dependencies: STRUCT_CMDS ------------------------------------------ Command: ELSEIF Description: ELSEIF introduces a secondary condition in a multi- line IF statement. Dependencies: STRUCT_CMDS ------------------------------------------ Command: END IF | FUNCTION | SELECT | SUB Description: END IF ends a multi-line IF statement. END FUNCTION ends a multi-line function definition. END SELECT ends a SELECT CASE statement. END SUB ends a multi- line subroutine definition. Dependencies: STRUCT_CMDS ------------------------------------------ Command: ENVIRON variable-string$ = string$ Description: ENVIRON sets the environment variable identified by variable-string$ to string$. It might be noted that this differs from the implementation of ENVIRON in some versions of BASIC, but bwBASIC's ENVIRON allows BASIC variables to be used on either side of the equals sign. Note that the function ENVIRON$() is different from the command, and be aware of the fact that in some operating systems an environment variable set within a program will not be passed to its parent shell. Dependencies: UNIX_CMDS ------------------------------------------ Function: ENVIRON$( variable-string$ ) Description: ENVIRON$ returns the environment variable associated with the name variable-string$. Dependencies: MS_FUNCS ------------------------------------------ Function: EOF( device-number ) Description: EOF returns TRUE (-1) if the device associated with device-number is at the end-of-file, otherwise it returns FALSE (0). Dependencies: MS_FUNCS ------------------------------------------ Command: ERASE variable[, variable]... Description: ERASE eliminates arrayed variables from a program. Dependencies: COMMON_CMDS ------------------------------------------ Function: ERL Description: ERL returns the line number of the most recent error. Dependencies: MS_FUNCS ------------------------------------------ Function: ERR Description: ERR returns the error number of the most recent error. Note that if PROG_ERRORS has been defined when bwBASIC is compiled, the ERR variable will not be set correctly upon errors. It only works when standard error messages are used. Dependencies: MS_FUNCS ------------------------------------------ Command: ERROR number Description: ERROR simulates an error, i.e., displays the message appropriate for that error. This command is helpful in writing ON ERROR GOSUB routines that can identify a few errors for special treatment and then ERROR ERR (i.e., default handling) for all others. Dependencies: COMMON_CMDS ------------------------------------------ Command: EXIT [FOR] Description: EXIT by itself exits from a DO...LOOP loop; EXIT FOR exits from a FOR...NEXT loop. Dependencies: STRUCT_CMDS ------------------------------------------ Function: EXP( number ) Description: EXP returns the exponential value of 'number'. Dependencies: (core) ------------------------------------------ Command: FIELD [#] device-number, number AS string-variable$ [, number AS string-variable$...] Description: FIELD allocates space in a random file buffer for device indicated by device-number, allocating 'number' bytes and assigning the bytes at this position to the variable string-variable$. Dependencies: COMMON_CMDS ------------------------------------------ Command: FILES filespec$ Description: FILES is a pseudocommand that invokes the directory program specified in the variable BWB.FILES$ with the argument filespec$. Normally, the user must set this variable before FILES can be used. E.g., for PC-type computers, BWB.FILES$ = "DIR" will work, for Unix machines, BWB.FILES$ = "ls -l" etc. Dependencies: COMMON_CMDS ------------------------------------------ Command: FNCS Description: CMDS is a debugging command that prints a list of all pre-defined bwBASIC functions. Dependencies: DEBUG ------------------------------------------ Command: FUNCTION Description: FUNCTION introduces a function definition, normally ending with END FUNCTION. In bwBASIC, FUNCTION and DEF are qorking equivalents, so either can be used with single-line function definitions or with multi- line definitions terminated by END FUNCTION. Dependencies: STRUCT_CMDS ------------------------------------------ Command: FOR counter = start TO finish [STEP increment] Description: FOR initiates a FOR-NEXT loop with the variable 'counter' initially set to 'start' and incrementing in 'increment' steps (default is 1) until 'counter' equals 'finish'. Dependencies: (core) ------------------------------------------ Command: GET [#] device-number [, record-number] Description: GET reads the next reacord from a random-access file or device into the buffer associated with that file. If record-number is specified, the GET command reads the specified record. Dependencies: COMMON_CMDS ------------------------------------------ Command: GOSUB line | label Description: GOSUB initiates a subroutine call to the line (or label) specified. The subroutine must end with RETURN. Dependencies: (core), but STRUCT_CMDS for labels ------------------------------------------ Command: GOTO line | label Description: GOTO branches program execution to the specified line (or label). Dependencies: (core), but STRUCT_CMDS for labels ------------------------------------------ Function: HEX$( number ) Description: HEX$ returns a string giving the hexadecimal (base 16) value for the 'number'. Dependencies: MS_FUNCS ------------------------------------------ Command: IF expression THEN [statement [ELSE statement]] Description: IF evaluates 'expression' and performs the THEN statement if it is true or (optionally) the ELSE statement if it is FALSE. If STRUCT_CMDS is set to TRUE, bwBASIC allows multi-line IF statements with ELSE and ELSEIF cases, ending with END IF. Dependencies: (core), STRUCT_CMDS for multi-line IF statements ------------------------------------------ Function: INKEY$ Description: INKEY$ reads the status of the keyboard, and a single keypress, if available. If a keypress is not available, then INKEY$ immediately returns a null string (""). Currently (v2.10) implemented in bwx_iqc.c only. Dependencies: IMP_IQC and IMP_CMDLOC ------------------------------------------ Command: INPUT [# device-number]|[;]["prompt string";]list of variables Description: INPUT allows input from the terminal or a device specified by device-number. If terminal, the "prompt string" is output, and input is assigned to the appropriate variables specified. bwBASIC does not support the optional feature of INPUT that suppresses the carriage-return and line-feed at the end of the input. This is because C alone does not provide for any means of input other than CR-LF-terminated strings. Dependencies: (core) ------------------------------------------ Function: INSTR( [start-position,] string-searched$, string-pattern$ ) Description: INSTR returns the position at which string-pattern$ occurs in string-searched$, beginning at start-position. As implemented in bwBASIC, INSTR cannot be used for assignments. Note: bwBASIC presently (v2.10) does not allow assignment to a function. Dependencies: MS_FUNCS ------------------------------------------ Function: INT( number ) Description: INT returns the largest integer less than or equal to the argument 'number'. NOTE that this is not a "truncated" integer function, for which see CINT. Dependencies: (core) ------------------------------------------ Command: KILL file-name$ Description: KILL deletes the file specified by file-name$. Dependencies: UNIX_CMDS ------------------------------------------ Function: LEFT$( string$, number-of-spaces ) Description: LEFT$ returns a substring a string$ with number-of-spaces from the left (beginning) of the string). As implemented under bwBASIC, it cannot be used for assignment. Dependencies: MS_FUNCS ------------------------------------------ Function: LEN( string$ ) Description: LEN returns the length in bytes of string$. Dependencies: COMMON_FUNCS ------------------------------------------ Command: LET variable = expression Description: LET assigns the value of 'expression' to the variable. As currently implemented, bwBASIC supports implied LET statements (e.g., "X = 4.5678" at the beginning of a line or line segment, but does not support assignment to multiple variables (e.g., "x, y, z = 3.141596"). Dependencies: (core) ------------------------------------------ Command: LINE INPUT [[#] device-number,]["prompt string";] string-variable$ Description: LINE INPUT reads entire line from the keyboard or a file or device into string-variable$. If input is from the keyboard (stdin), then "prompt string" will be printed first. Unlike INPUT, LINE INPUT reads a whole line, not stopping for comma-delimited data items. Dependencies: COMMON_CMDS ------------------------------------------ Command: LIST line[-line] Description: LIST lists program lines as specified in its argument. Dependencies: INTERACTIVE ------------------------------------------ Command: LOAD file-name Description: LOAD loads an ASCII BASIC program into memory. Dependencies: INTERACTIVE ------------------------------------------ Function: LOC( device-number ) Description: LOC returns the next record that GET or PUT statements will use. Dependencies: MS_FUNCS ------------------------------------------ Command: LOCATE line, column Description: LOCATE addresses trhe curor to a specified line and column. Currently (v2.10) implemented in bwx_iqc.c only. Dependencies: IMP_IQC and IMP_CMDLOC ------------------------------------------ Function: LOF( device-number ) Description: LOF returns the length of a file (specified by device-number) in bytes. Dependencies: MS_FUNCS ------------------------------------------ Function: LOG( number ) Description: LOG returns the natural logarithm of the argument 'number'. Dependencies: (core) ------------------------------------------ Command: LOOP [UNTIL expression] Description: LOOP terminates a program loop: see DO. Dependencies: STRUCT_CMDS ------------------------------------------ Command: LSET string-variable$ = expression Description: LSET transfers data from 'expression' to the left-hand side of a string variable or random access buffer field. Dependencies: COMMON_CMDS ------------------------------------------ Command: MERGE file-name Description: MERGE adds program lines from 'file-name' to the program in memory. Unlike LOAD, it does not clear the program currently in memory. Dependencies: COMMON_CMDS ------------------------------------------ Function: MID$( string$, start-position-in-string[, number-of-spaces ] ) Description: MID$ returns a substring of string$ beginning at start-position-in-string and continuing for number-of-spaces bytes. Dependencies: MS_FUNCS ------------------------------------------ Command: MKDIR pathname$ Description: MKDIR creates a new directory path as specified by pathname$. Dependencies: UNIX_CMDS ------------------------------------------ Function: MKD$( number ) Description: MKD$, MKI$, and MKS$ are all equivalent in bwBASIC. They convert the numerical value 'number' into a string which can be stored in a more compressed form in a file (especially for random file access). Since bwBASIC does not recognize differences in precision, these commands are effectively equivalent. Dependencies: MS_FUNCS ------------------------------------------ Function: MKI$( number ) Description: Equivalent to MKD$ (q.v.) Dependencies: MS_FUNCS ------------------------------------------ Function: MKS$( number ) Description: Equivalent to MKD$ (q.v.). Dependencies: MS_FUNCS ------------------------------------------ Command: NAME old-file-name AS new-file-name Description: NAME renames an existing file (old-file-name) as new-file-name. Dependencies: UNIX_CMDS ------------------------------------------ Command: NEW Description: NEW deletes the program in memory and clears all variables. Dependencies: INTERACTIVE ------------------------------------------ Command: NEXT [counter-variable] Description: NEXT comes at the end of a FOR-NEXT loop; see FOR. Dependencies: (core) ------------------------------------------ Function: OCT$( number ) Description: OCT$ returns a string giving the octal (base 8) representation of 'number'. Dependencies: MS_FUNCS ------------------------------------------ Command: ON variable GOTO|GOSUB line[,line,line,...] Description: ON either branches (GOTO) or calls a subroutine (GOSUB) based on the rounded value of variable; if it is 1, the first line is called, if 2, the second line is called, etc. Dependencies: (core) ------------------------------------------ Command: ON ERROR GOSUB line|label Description: ON ERROR sets up an error handling subroutine. See also ERROR. Dependencies: COMMON_CMDS, STRUCT_CMDS for labels ------------------------------------------ Command: OPEN "O"|"I"|"R", [#]device-number, file-name [,record length] file-name FOR INPUT|OUTPUT|APPEND AS [#]device-number [LEN = record-length] Description: OPEN allocates random access memory for access to a disk file or other device. Note that two quite different forms of the OPEN statement are supported. In the first form, "O" (note that these letters must be encased in quotation marks) denotes sequential output, "I" denotes sequential input, and "R" denotes random-access input and output. Once OPEN, any number of operations can be performed on a device (see WRITE #, INPUT #, PRINT #, etc.). Dependencies: COMMON_CMDS ------------------------------------------ Command: OPTION BASE number Description: OPTION BASE sets the lowest value for array subscripts, either 0 or 1. Dependencies: (core) ------------------------------------------ Function: POS Description: POS returns the current cursor position in the line. Dependencies: COMMON_FUNCS ------------------------------------------ Command: PRINT [# device-number,][USING format-string$;] expressions... Description: PRINT outputs text to the screen or to a file or device specified by device-number. In the current implementation of bwBASIC, expressions to be printed must be separated by the comma (tabbed output), the semicolon (immediate sequential output) or the plus sign (immediate sequential output by string concatenation). Expressions separated by blanks or tabs are not supported. If USING is specified, a number of formatting marks may appear in the format string: ! prints the first character of a string \ prints 2+x characters of a string, where x = the number of spaces between the backslashes & variable-length string field # represents a single digit in output format for a number . decimal point in a number + sign of a number (will output + or -) - trailing minus after a number ** fill leading spaces with asterisks $$ output dollar sign in front of a number ^^ output number in exponential format _ output next character literally As currently implemented, the exponential format will be that used by the C compiler. Dependencies: (core), COMMON_FUNCS for USING ------------------------------------------ Command: PUT [#] device-number [, record-number] Description: PUT outputs the next available record or the record specified by record-number to the file or device denoted by device-number. Dependencies: COMMON_CMDS ------------------------------------------ Command: QUIT Description: QUIT is a synonym for SYSTEM; with INTERACTIVE environment, it exits the program to the operating system (or the calling program). Dependencies: INTERACTIVE ------------------------------------------ Command: RANDOMIZE number Description: RANDOMIZE seeds the random number generator (see RND). Under bwBASIC, the TIMER function (q.v.) can be used to supply a 'number' seed for the random number generator. Dependencies: (core) ------------------------------------------ Command: READ variable[, variable]... Description: READ reads values from DATA statements and assigns these values to the named variables. Variable types in a READ statement must match the data types in DATA statements as they are occurred. See also DATA and RESTORE. Dependencies: (core) ------------------------------------------ Command: REM string Description: REM allows remarks to be included in a program. As currently implemented, the entire line following REM is ignored by the interpreter (thus, even if MULTISEG_LINES is set, a REM line will not be able to find a segment delimiter (":") followed by another line segment with command. bwBASIC does not currently implement the Microsoft-style use of the single quotation mark to denote remarks. Dependencies: (core) ------------------------------------------ Command: RESTORE line Description: RESTORE resets the line and position counters for DATA and READ statements to the top of the program file or to the beginning of the specified line. (Currently this must be a line number.) Dependencies: (core) ------------------------------------------ Command: RETURN Description: RETURN concludes a subroutine called by GOSUB. Dependencies: (core) ------------------------------------------ Function: RIGHT$( string$, number-of-spaces ) Description: RIGHT$ returns a substring a string$ with number-of-spaces from the right (end) of the string). As implemented under bwBASIC, it cannot be used for assignment. Dependencies: MS_FUNCS ------------------------------------------ Command: RMDIR pathname Description: RMDIR deletes the directory path indicated by pathname. Dependencies: UNIX_CMDS ------------------------------------------ Function: RND( number ) Description: RND returns a pseudo-random number. The 'number' value is ignored by bwBASIC if supplied. The RANDOMIZE command (q.v.) reseeds the random-number generator. Dependencies: (core) ------------------------------------------ Command: RSET string-variable$ = expression Description: RSET transfers data from 'expression' to the right-hand side of a string variable or random access buffer field. Dependencies: COMMON_CMDS ------------------------------------------ Command: RUN [line][file-name$] Description: RUN executes the program in memory. If a file-name$ is supplied, then the specified file is loaded into memory and executed. If a line number is supplied, then execution begins at that line. Dependencies: INTERACTIVE ------------------------------------------ Command: SAVE file-name$ Description: SAVE saves the program in memory to file-name$. bwBASIC only saves files in ASCII format. Dependencies: INTERACTIVE ------------------------------------------ Command: SELECT CASE expression Description: SELECT CASE introduces a multi-line conditional selection statement. The expression given as the argument to SELECT CASE will be evaluated by CASE statements following. The SELECT CASE statement conclludes with an END SELECT statement. As currently implemented, CASE statements may be followed by string values, but in this case only simple comparisons (equals, not equals) can be performed. Dependencies: STRUCT_CMDS ------------------------------------------ Function: SGN( number ) Description: SGN returns the sign of the argument 'number', +1 for positive numbers, 0 for 0, and -1 for negative numbers. Dependencies: (core) ------------------------------------------ Function: SIN( number ) Description: SIN returns the sine of the argument 'number' in radians. Dependencies: (core) ------------------------------------------ Function: SPACE$( number ) Description: SPACE$ returns a string of blank spaces 'number' bytes long. Dependencies: MS_FUNCS ------------------------------------------ Function: SPC( number ) Description: SPC returns a string of blank spaces 'number' bytes long. Dependencies: MS_FUNCS ------------------------------------------ Function: SQR( number ) Description: SQR returns the square root of the argument 'number'. Dependencies: (core) ------------------------------------------ Command: STOP Description: STOP interrupts program execution. As implemented under bwBASIC, STOP issues a SIGINT signal. Dependencies: (core) ------------------------------------------ Function: STR$( number ) Description: STR$ returns a string giving the decimal (base 10) representation of the argument 'number'. Dependencies: COMMON_FUNCS ------------------------------------------ Function: STRING$( number, ascii-value|string$ ) Description: STRING$ returns a string 'number' bytes long consisting of either the first character of string$ or the character answering to the ASCII value ascii-value. Dependencies: MS_FUNCS ------------------------------------------ Command: SUB subroutine-name Description: SUB introduces a named, multi-line subroutine. The subroutine is called by a CALL statement, and concludes with an END SUB statement. Dependencies: STRUCT_CMDS ------------------------------------------ Command: SWAP variable, variable Description: SWAP swaps the values of two variables. The two variables must be of the same type (either numerical or string). Dependencies: COMMON_CMDS ------------------------------------------ Command: SYSTEM Description: SYSTEM exits from bwBASIC to the calling program or (more usually) the operating system. Dependencies: INTERACTIVE ------------------------------------------ Function: TAB( number ) Description: TAB outputs spaces until the column indicated by 'number' has been reached. Dependencies: (core) ------------------------------------------ Function: TAN( number ) Description: TAN returns the tangent of the argument 'number' in radians. Dependencies: (core) ------------------------------------------ Function: TIME$ Description: TIME$ returns the current time based on the computer's internal clock as a string in the form "HH-MM-SS". As implemented under bwBASIC, TIME$ cannot be used for assignment (i.e., to set the system time). Note: bwBASIC presently (v2.10) does not allow assignment to a function. Dependencies: COMMON_FUNCS ------------------------------------------ Function: TIMER Description: TIMER returns the time in the system clock in seconds elapsed since midnight. Dependencies: MS_FUNCS ------------------------------------------ Command: TROFF Description: TROFF turns of the trace facility; see TRON. Dependencies: COMMON_CMDS ------------------------------------------ Command: TRON Description: TRON turns on the trace facility. This facility will print each line number in square brackets as the program is executed. This is useful in debugging programs with line numbers. To debug an unnumbered program with TRON, call DO NUM first, but remember to call DO UNNUM before you save the program later. Dependencies: COMMON_CMDS ------------------------------------------ Function: VAL( string$ ) Description: VAL returns the numerical value of the string$. Dependencies: COMMON_FUNCS ------------------------------------------ Command: VARS Description: VARS is a debugging command which prints a list of all variables defined which have global scope. Dependencies: DEBUG ------------------------------------------ Command: WEND Description: WEND concludes a WHILE-WEND loop; see WHILE. Dependencies: COMMON_CMDS ------------------------------------------ Command: WHILE expression Description: WHILE initiates a WHILE-WEND loop. The loop ends with WEND, and execution reiterates through the loop as long as the 'expression' is TRUE (-1). Dependencies: COMMON_CMDS ------------------------------------------ Command: WIDTH [# device-number,] number Description: WIDTH sets screen or device output to 'number' columns. device-number specifies the device or file for oputput. Dependencies: COMMON_CMDS ------------------------------------------ Command: WRITE [# device-number,] element [, element ].... Description: WRITE outputs variables to the screen or to a file or device specified by device-number. Commas are inserted between expressions output, and strings are enclosed in quotation marks. Dependencies: COMMON_CMDS ------------------------------------------

PREDEFINED VARIABLES
BWB.EDITOR$ BWB.FILES$ BWB.PROMPT$ BWB.IMPLEMENTATION$ The commands EDIT and FILES are pseudo-commands that launch shell programs named in the variables BWB.EDITOR$ and BWB.FILES$, respectively. The default values for these variables can be changed in bwbasic.h (DEF_EDITOR and DEF_FILES), or they can be changed on the fly by the user. An idea might be to initialize these variables in "profile.bas" for specific implementations; for instance, BWB.FILES$ might be defined as "ls -l" on Unix systems or "dir" on DOS systems. The preset variable BWB.PROMPT$ can be used to set the prompt string for bwBASIC. Again, it is suggested that a user- selected promptcan be set up in a "profile.bas" to be initialized each time bwBASIC starts. Note that special characters can be added to the prompt string, e.g., BWB.PROMPT$ = "Ok"+CHR$(10) will give an "Ok" prompt followed by a linefeed. The preset variable BWB.IMPLEMENTATION$ will return "TTY" for the bwx_tty implementation and will return "IQC" for the IBM PC or Compatibles with QuickC (bwx_iqc) implementation. This may be useful in determing which commands and functions (specifically CLS, LOCATE, and INKEY$) may be available.

UNIMPLEMENTED COMMANDS AND FUNCTIONS, and AGENDA FOR DEVELOPMENT
There are some items not implemented that have been so long a part of standard BASICs that their absence will seem surprising. In each case, though, their implementation would require opera- ting-system-specific functions or terminal-specific functions that cannot be universally provided. Some specific examples: CLOAD Relies on CP/M or MSDOS conventions for binary executable files. CONT See RESUME below (programmer ignorance?). DEF USR Relies on CP/M or MSDOS conventions for binary executable files. FRE() The ability to report the amount of free memory remaining is system-specific due to varying patterns of memory allocation and access; consequently this ability is not present in ANSI or earlier versions of C and this function is not available in bwBASIC. INPUT$() C by itself is not able to read unechoed keyboard input, and can read keyboard input only after a Carriage-Return has been entered. INP Calls to hardware ports, like machine-language routines, are highly system-specific and cannot be implemented in C alone. LLIST See LPRINT below. LPOS See LPRINT below. LPRINT and LLIST, etc., require access to a printer device, and this varies from one system to another. Users might try OPENing the printer device on their own operating system (e.g., "/dev/lp" on Unix systems, or "PRN" under DOS) and see if printing can be done from bwBASIC in this way. NULL In this case, I am convinced that NULL is no longer necessary, since very few printers now require NULLs at the end of lines. OUT See INP above (calls to hardware ports). PEEK() PEEK and POKE enabled earlier BASICs to address particular memory locations. Although bwBASIC could possibly implement this command (POKE) and this function (PEEK()), the limitation would be highly limited by the different systems for memory access in different systems. POKE see PEEK() above. RENUM Since unnumbered lines can be entered and executed under bwBASIC, it would not be possible to implement a RENUM routine. Instead, bwBASIC uses DO NUM and DO UNNUM. RESUME Is this possible under C? If so, I simply have failed to figure it out yet. Mea culpa (but not maxima). USR See CALL and DEF USR above (machine language subroutines). VARPTR See PEEK and POKE above. WAIT See INP and OUT above. There are other commands, functions, and implementation details that I am working on, and which are on the agenda list for future versions of bwBASIC. These agenda include: PARACT i.e., the ability to execute PARallel ACTions. This is described in ANSI BASIC, although I have not seen it implemented before. It will offer a rough, non- preemptive form of multitasking within the scope of a BASIC program. Programmers will note points at which there are already hooks for PARACT in bwBASIC. XMEM PC-type computers need to be able to use extended memory. If we could use extended memory for program lines, variables, and function defitions, we could write much longer programs. This would entail, however, a fairly serious rewriting of the program to utilize memory handles for these storage features instead of direct memory pointers. Windows The addition of memory handles in addition to the non-preemptive execution of program lines (in a crude form, already present) will make it possible to develop implementations for Windows and perhaps for other graphical user interfaces. But what form should this take? I have in mind presently a BASIC that would run in the background, appearing only as an icon in the GUI space, with pop-up editors and output windows. Thus, the interpreted language would serve a purpose something like 'cron' (a task scheduler) under Unix systems. You may have some reflections that would help me in this. Graphics Here we face fairly critical differences in different styles and implementations of graphics, e.g., between GWBASIC, ANSI BASIC, VisualBASIC, etc. But it's possible that Graphics commands and functions could be added. These would all be implementation-specific. The ANSI Standard for full BASIC does not specify which particular commands or functions must be implemented, and in fact the standard is very robust. Perhaps no implementation of BASIC would ever include all of the items, but some ANSI commands and functions which remain unimplemented are: ACCESS ANGLE AREA ARITHMETIC ARRAY ASK BSTR BVAL CEIL CELLS CLIP COLLATE CONNECT COSH DATUM DEBUG DECIMAL DECLARE DEGREES DEVICE DISCONNECT DISPLAY DOT DRAW ERASE EVENT EXCEPTION GRAPH HANDLER IMAGE KEY LCASE LINES LOG10 LOG2 MAT MIX MULTIPOINT OUTIN OUTPUT PARACT PICTURE PIXEL PLOT POINTS RADIANS RECEIVE RENUMBER REWRITE ROTATE ROUND SEIZE SEND SHIFT SINH TANH TIMEOUT TRACE TRANSFORM TRUNCATE UBOUND UCASE VIEWPORT WAIT VIEWPORT ZONEWIDTH

THE STORY OF BYWATER BASIC
This program was originally begun in 1982 by my grandmother, Mrs. Verda Spell of Beaumont, TX. She was writing the program using an ANSI C compiler on an Osborne I CP/M computer and although my grandfather (Lockwood Spell) had bought an IBM PC with 256k of RAM my grandmother would not use it, paraphrasing George Herbert to the effect that "He who cannot in 64k program, cannot in 512k." She had used Microsoft BASIC and although she had nothing against it she said repeatedly that she didn't understand why Digital Research didn't "sue the socks off of Microsoft" for version 1.0 of MSDOS and so I reckon that she hoped to undercut Microsoft's entire market and eventually build a new software empire on the North End of Beaumont. Her programming efforts were cut tragically short when she was thrown from a Beaumont to Port Arthur commuter train in the summer of 1986. I found the source code to bwBASIC on a single-density Osborne diskette in her knitting bag and eventually managed to have it all copied over to a PC diskette. I have revised it slightly prior to this release. You should know, though, that I myself am an historian, not a programmer.