Short BASIC program containing inline 6502 assembly |
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| Appeared in | 1981 |
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| Stable release | 5.90b |
| Influenced by | BASIC, Atom BASIC, BCPL |
| OS | BBC Micro MOS Technology 6502 RISC OS Sinclair ZX Spectrum CP/M DOS Microsoft Windows TI-83 Plus & TI-84 Plus |
| License | Proprietary |
| Website | http://www.bbcbasic.org |
BBC BASIC is a programming language, developed in 1981 as a native programming language for the MOS Technology 6502 based Acorn BBC Micro home/personal computer, mainly by Sophie Wilson. It is a version of the BASIC programming language adapted for a U.K. computer literacy project of the BBC.[1]
BBC BASIC, based on the older Atom BASIC (for the Acorn Atom), extended traditional BASIC with named DEF PROC/DEF FN procedures and functions, REPEAT UNTIL loops, and IF THEN ELSE structures inspired by COMAL. The interpreter also included powerful statements for controlling the BBC Micro's four-channel sound output and its low / high-resolution seven mode graphics display.
One of the unique features of BBC BASIC was the presence of an inline assembler allowing users to write 6502 assembly language programs. The assembler was fully integrated into the BASIC interpreter and shared variables with it. This allowed developers to write not just assembly language code, but also BASIC code to emit assembly language, making it possible to use code generation techniques and even write simple compilers in BASIC.
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In 1978 Hermann Hauser and Andy Hopper (while at Cambridge University), founded Acorn Computers. Andy Hopper is now the head of the University of Cambridge Computer Laboratory.[2] Much of the code was developed at Cambridge University by Sophie Wilson[3] and her colleagues.[4]
BASIC I, the original version, was shipped on early BBC Micros.
BASIC II was used on the Acorn Electron and BBC Micros shipped after 1982, including the BBC B+. It added the OPENUP OSCLI keywords, along with offset assembly and bug fixes.
BASIC III, was produced in both a UK version and a US market version for Acorn's abortive attempt to enter the cross-Atlantic computer market. Apart from a few bug fixes, the only change from BASIC II was that the COLOUR command could also be spelled COLOR: regardless of which was input, the UK version always listed it as COLOUR, the US version as COLOR. The main place that BASIC III can be found is as the HI-BASIC version for the external second processor.
BASIC IV, also known as CMOS BASIC, available on the BBC Master and Master Compact machines, was changed to use the new instructions available in the 65SC12 processor, reducing the size of the code and therefore allowing the inclusion of LIST IF, EXT# as a statement, EDIT, TIME$, ON PROC, | in VDU statements and faster floating point. Bug fixes were again included.
HI-BASIC: this was available in two versions, the first based on BASIC III, and the second based on BASIC IV. Both were built to run from a higher address (&B800) on the second processor, rather than the usual &8000 address on the BBC B. This allowed more program space to be available on either the external or internal 6502 Second Processors. A version was introduced to support a second Z80 processor.[5]
Another version of BBC BASIC, called BAS128, was supplied on tape and disc with the BBC Master and Master Compact; it loaded into main RAM and used the 64 kB of Sideways RAM for user programs. This provided support for much larger programs at the cost of being a lot slower than the normal ROM-based version.
With the move to the 32 bit ARM CPU and the removal of the 16kB limit on the BASIC code size many new features were added.[6] BASIC V version 1.04 was 61kB long. Current versions of RISC OS still contain a BBC BASIC interpreter. The source code to the RISC OS 5 version of BBC BASIC V has been released as 'shared source' by RISC OS Open. In 2011 TBA Software released test versions of an updated BASIC which includes support for VFP/NEON from assembler.[7]
Amongst the new commands and features supported were:
WHILE-ENDWHILEIF-THEN-ELSE-ENDIFCASE-OF-WHEN-OTHERWISE-ENDCASE,RETURN parameters in procedures,LIBRARY,INSTALL and OVERLAY),LOCAL DATA and LOCAL ERROR handlers,RESTORE,STEP TRACE,The graphics commands were entirely backwards compatible, the sound less so (for example, the ENVELOPE keyword from BASIC V onwards is a command which takes fourteen numeric parameters and effectively does nothing - as in older versions, it calls OS_Word 8, but that does nothing on RISC OS [1][2]). The in-line in 6502 assembler was replaced by an ARM assembler. BASIC V was said, by Acorn, to be "certainly the fastest interpreted BASIC in the world" and "probably the most powerful BASIC found on any computer".
BASIC VI is a version of BASIC V that supports 8 byte format real numbers (according to IEEE standard 754) as opposed to the standard 5 byte format introduced in BASIC I.
BBC BASIC V and VI were delivered as standard on the Acorn Archimedes and the Risc PC. A version of BBC BASIC V was also available to run on the ARM second processor for the BBC Micro.
A Compiler for BBC Basic V was produced by Paul Fellows, team leader of the Arthur OS development, and published initially by DABS Press. This was able to implement almost all of the language, with the obvious exception of the EVAL function - which inevitably required run-time programatic interpretation. As evidence of its completeness, it was able to support things like the in-line assembler syntax. Interestingly the compiler was written in BBC Basic. The compiler (running under the interpreter in the early development stages) was able to compile itself and verions that were distributed were self-compiled object code. Many applications initially written to run under the interpreter benefitted from the performance boost that this gave, putting BBC Basic on a par with other languages for serious application development.
BBC BASIC has also been ported to many other platforms.[8]
In addition to the version of BBC BASIC supplied with the BBC Micro's Z80 Second processor, a Z80 based version of BBC BASIC also exists for CP/M based systems. Until recently no version existed for the Sinclar ZX Spectrum, however due to efforts of J.G Harston (also responsible for a PDP-11 version), BBC BASIC for the Spectrum was released in January 2002 with many improvements made in subsequent releases.
A Zilog Z80 version of BBC BASIC was also used on the Tiki 100 desktop computer, Cambridge Z88 portable and the Amstrad NC100 Notepad and Amstrad NC200 Notebook computers. This version has been implemented on the TI-83 Plus and TI-84 Plus series graphing calculators.
For PC based systems, BBC BASIC was also implemented for DOS as BBCBASIC (86) (which aimed for maximum compatibility with the BBC Micro) and BBasic (which concentrated on the BASIC language itself, with its own enhancements based on BASIC II).
A version of BBC BASIC integrated with the Microsoft Windows graphical user interface, BBC BASIC for Windows created by Richard Russell (who also developed the Z80 and x86 versions), was released in 2001. This version is still under active development, seeing much industry use currently. Whilst supporting nearly completely the original BBC BASIC specification (BASIC IV), the Windows version supports much of BASIC V/VI syntax as well as some advanced features of its own. Features unique to BBC BASIC for Windows include interpreter support for record/structure types, and the ability to call Windows API routines or those in an external DLL. Recent versions have included advanced features comparable with languages like C.
A GPL clone of BBC BASIC named Brandy written in portable C is also available.[9][10][11][12]
An emulator of the BBC Micro for the Commodore Amiga was produced by Ariadne Software for CBM (UK). While extremely fast, it did not emulate the 6502 at full speed so assembly code would run slower than a real BBC while BASIC programs would run much faster, unfortunately due to the way the optimized Basic and the 6502 emulation interacted, almost no commercial games would run (but well behaved code and educational software generally worked); additionally it used a slightly less precise floating-point numeric format. For a while it was bundled with a special academic package of the Amiga 500, in the hope that schools would replace their aging BBC Bs with Amiga 500s.
A version of BBC BASIC (Z80) has also been made for the TI-83/84+ Texas Instruments calculator families by Benjamin Ryves.
A Commodore 64 version was produced by a small software house Aztec Software in the early 80s.
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