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(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$. Dependencies: COMMON_FUNCS ------------------------------------------ Command: VARS Description: VARS is a debugging command which prints a list of all variables defined which have global scope. Dependencies: DEBUG ------------------------------------------ Command: WEND Description: WEND concludes a WHILE-WEND loop; see WHILE. Dependencies: COMMON_CMDS ------------------------------------------ Command: WHILE expression Description: WHILE initiates a WHILE-WEND loop. The loop ends with WEND, and execution reiterates through the loop as long as the 'expression' is TRUE (-1). Dependencies: COMMON_CMDS ------------------------------------------ Command: WIDTH [# device-number,] number Description: WIDTH sets screen or device output to 'number' columns. device-number specifies the device or file for oputput. Dependencies: COMMON_CMDS ------------------------------------------ Command: WRITE [# device-number,] element [, element ].... Description: WRITE outputs variables to the screen or to a file or device specified by device-number. Commas are inserted between expressions output, and strings are enclosed in quotation marks. Dependencies: COMMON_CMDS ------------------------------------------6. PREDEFINED VARIABLES BWB.EDITOR$ 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$) may be available. 7. UNIMPLEMENTED COMMANDS AND FUNCTIONS, and AGENDA FOR DEVELOPMENT There are some items not implemented that have been so long a part of standard BASICs that their absence will seem surprising. In each case, though, their implementation would require opera- ting-system-specific functions or terminal-specific functions that cannot be universally provided. Some specific examples: CLOAD Relies on CP/M or MSDOS conventions for binary executable files. CONT See RESUME below (programmer ignorance?). DEF USR Relies on CP/M or MSDOS conventions for binary executable files. FRE() The ability to report the amount of free memory remaining is system-specific due to varying patterns of memory allocation and access; consequently this ability is not present in ANSI or earlier versions of C and this function is not available in bwBASIC. INPUT$() 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 ZONEWIDTH8. 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.9. COMMUNICATIONS: email: tcamp@delphi.com⌨️ 快捷键说明
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