Power-Programmierung/CD1.mdf/basic/interpre/bwbasic/bwbasic.doc

Text File | 1992-10-27 | 17KB | 442 lines

               Bywater BASIC Interpreter/Shell, version 1.10
               ---------------------------------------------

                    Copyright (c) 1992, Ted A. Campbell
                 for bwBASIC version 1.10, 1 November 1992


CONTENTS:

   1. DESCRIPTION
   2. TERMS OF USE
   3. COMMANDS AND FUNCTIONS IMPLEMENTED
   4. SOME NOTES ON USAGE
   5. UNIMPLEMENTED COMMANDS AND FUNCTIONS
   6. SOME NOTES ON COMPILATION
   7. THE STORY OF BYWATER BASIC
   8. COMMUNICATIONS


1. DESCRIPTION

   The Bywater BASIC Interpreter (bwBASIC) implements a large
   superset of the ANSI Standard for Minimal BASIC (X3.60-1978)
   in ANSI C and offers shell program facilities as an extension
   of BASIC.

   The set of BASIC commands and functions implemented is fairly
   limited (see section three below), although more commands and
   functions are implemented than appear in the specification
   for Minimal BASIC. There are no commands that are terminal- or
   hardware specific. (Seriously -- CLS may work under bwBASIC
   on your DOS-based pc, but that is because bwBASIC shells
   out to DOS when it does not recognize CLS and executes CLS there.)

   The interpreter is 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.


2. TERMS OF USE:

   The bwBASIC source code and executables produced from it can be
   used subject to the following statement which is included in
   the header to all the source code files:

        All U.S. and international copyrights are claimed by the
        author. The author grants permission to use this code
        and software based on it under the following conditions:
        (a) in general, the code and software based upon it may be
        used by individuals and by non-profit organizations; (b) it
        may also be utilized by governmental agencies in any country,
        with the exception of military agencies; (c) the code and/or
        software based upon it may not be sold for a profit without
        an explicit and specific permission from the author, except
        that a minimal fee may be charged for media on which it is
        copied, and for copying and handling; (d) the code must be
        distributed in the form in which it has been released by the
        author; and (e) the code and software based upon it may not
        be used for illegal activities.


3. BASIC COMMANDS AND FUNCTIONS IMPLEMENTED:

   ABS( number )
   ASC( string$ )
   ATN( number )
   CHAIN [MERGE] file-name [, line-number] [, ALL]
   CHR$( number )
   CINT( number )
   CLEAR
   CLOSE [[#]file-number]...
   COMMON variable [, variable...]
   COS( number )
   CSNG( number )
   CVD( string$ )
   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...)]...
   END
   ENVIRON variable-string = string
   ENVIRON$( variable-string )
   EOF( device-number )
   ERASE variable[, variable]...
   ERL
   ERR
   ERROR number
   EXP( number )
   FIELD [#] device-number, number AS string-variable [, number AS string-variable...]
   FOR counter = start TO finish [STEP increment]
   GET [#] device-number [, record-number]
   GOSUB line
   GOTO line
   HEX$( number )
   IF expression THEN statement [ELSE statement]
   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 )
   LOF( device-number )
   LOG( number )
   LSET string-variable$ = expression
   MERGE file-name
   MID$( string$, start-position-in-string[, number-of-spaces ] )
   MKD$( double-value# )
   MKI$( integer-value% )
   MKS$( single-value! )
   NAME old-file-name AS new-file-name
   NEW
   NEXT counter
   OCT$( 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$;] expressions...
   PUT [#] device-number [, record-number]
   RANDOMIZE number
   READ variable[, variable]...
   REM string
   RESTORE line
   RETURN
   RIGHT$( string$, number-of-spaces )
   RND( number )
   RSET string-variable$ = expression
   RUN [line][file-name]
   SAVE file-name
   SGN( number )
   SIN( number )
   SPACE$( number )
   SPC( number )
   SQR( number )
   STOP
   STR$( number )
   STRING$( number, ascii-value|string$ )
   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 ]....

   If DIRECTORY_CMDS is set to TRUE when the program is compiled,
   then the following commands will be available:

   CHDIR pathname
   MKDIR pathname
   RMDIR pathname

   If DEBUG is set to TRUE when the program is compiled then
   the following debugging commands (unique to bwBASIC) will
   be available:

   VARS            (prints a list of all variables)
   CMDS            (prints a list of all commands)
   FNCS            (prints a list of all functions)

   If COMMAND_SHELL is set to TRUE when the program is compiled,
   then the user may enter a shell command at the bwBASIC prompt.


4. SOME NOTES ON USAGE:

   An interactive environment is provided, 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. In this case,
   however, one will not be able to alter the numberless lines
   within the interactive environment.

   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.

   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".

   All programs are stored as ASCII text files.

   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).

   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.

   Notes on the implementation of specific commands:

   CVI(), CVD(), 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.

   ENVIRON:  The ENVIRON command requires BASIC strings on either
   side of the equals sign.  Thus:

      environ "PATH" = "/usr/bin"

   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.

   ERR: 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.

   FOR and NEXT:  In this implementation of bwBASIC, a NEXT
   statement must appear in the first position in a program
   line; it cannot appear in a line segment beyond a colon.

   INPUT: bwBASIC cannot support the optional feature of INPUT
   that suppresses the carriage-return and line-feed at the end
   of the input.  This is because ANSI C does not provide for any
   means of input other than CR-LF-terminated strings.


5. UNIMPLEMENTED COMMANDS AND FUNCTIONS

   There are a few 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 ANSI C cannot provide. Some specific examples:

   CALL        In some versions of BASIC, CALL is used to call a
        machine language subroutine, but machine language
        routines are highly system-specific.  In other
        BASICs (conforming to the more complete ANSI
        definition of BASIC), CALL is used to call a
        named subroutine.  Although it's possible that
        bwBASIC could develop as a numberless BASIC
        with named subroutine calls, these features
        are not implemented in this earliest released
        version.

   CLOAD    See CALL above (machine language subroutines).

   CONT        See RESUME below (programmer ignorance?).

   DEF USR    See CALL above (machine language subroutines).

   EDIT        EDIT would be especially nice, but requires some
           specific knowledge of how particular computers
           handle interaction between the screen and the
           keyboard.  This knowledge isn't available within
           the bounds of ANSI C alone ("innerhalb die Grenzen
        der reinen Vernunft," with apologies to Immanuel
        Kant).

   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 C and this function
        is not available in bwBASIC.

   FILES    The FILES command requires a list of files conforming
           to a specifier; ANSI C does not provide this. When
           COMMAND_SHELL is defined as TRUE, users might want
           to issue operating-system commands such as "DIR"
           (DOS) or "ls -l" (Unix) to get a list of files.

   INKEY$    This function requires a keyboard scan to indicate
        whether a key is pending. Although this facility
        is easily available on microcomputers (it is part
        of the minimal CP/M Operating System), it is not
        easily available on some more complex systems.
        Consequently, it's not part of the C standard and
        bwBASIC has not implemented INKEY$.

   INPUT$()    Similar to INKEY$ above, ANSI 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 ANSI 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.

   RESUME    Is this possible under ANSI 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.


6. SOME NOTES ON COMPILATION

   bwBASIC is written in ANSI C and takes advantage of some of the
   enhancements of ANSI C over the older K&R standard.  The program
   expects to find standard ANSI C include files (such as <stddef.h>).
   Because there is nothing terminal- or hardware-specific about it,
   I should hope that it would compile correctly under any ANSI C
   compiler, but you may have to construct your own makefile.

   Two makefiles are currently provided: "makefile.qcl" will compile
   the program utilizing the Microsoft QuickC (tm) line-oriented
   compiler on DOS-based p.c.'s, and "makefile.gcc" will compile
   the program utilizing the ANSI option of Gnu C++. I have also
   compiled the program utilizing Borland's Turbo C++ (tm) on DOS-
   based machines.

   No alterations to flags are necessary for varied environments,
   but the beginning of file <bwbasic.h> allows the user to set
   some debugging flags and to control some program defaults.
   The file <bwb_mes.h> has a number of language-specific message
   sets that can be controlled by setting the appropriate language
   flag.


7. 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.


8. COMMUNICATIONS:

   Ted A. Campbell
   Bywater Software
   P.O. Box 4023
   Duke Station
   Durham, NC  27706
   USA

   email:  [e-mail]