BBC BASIC

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BBC BASIC was developed in 1981 as a native programming language for the MOS Technology 6502 based Acorn BBC Micro home/personal computer, mainly by Roger Wilson. It was a version of the BASIC programming language adapted for a U.K. computer literacy project of the BBC.

BBC BASIC, based on the older Atom BASIC (for the Acorn Atom), extended traditional BASIC with named 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 high-resolution 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.

1 BBC Micro versions
2 Acorn Archimedes (RISC OS) versions
3 BBC BASIC on other platforms
4 External links

[edit] BBC Micro versions

BASIC I, the original version, available on early BBC Micros, was superseded by BASIC II (used on the Acorn Electron and BBC Micros shipped after 1982). It added the OPENUP and OSCLI keywords, along with offset assembly and bug fixes.

BASIC III, the release supplied with the BBC B+, was produced in both a UK version and a U.S. 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. This was the only difference between the two versions.

BASIC IV, also known as CMOS BASIC, available on the BBC Master and BBC Master Compact machines, was changed to use the new instructions available in the 65C12 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.

[edit] Acorn Archimedes (RISC OS) versions

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. BASIC V version 1.04 was 61kB long.

Amongst the new commands and features supported were:

WHILE-ENDWHILE
IF-THEN-ELSE-ENDIF
CASE-OF-WHEN-OTHERWISE-ENDCASE,
RETURN parameters in procedures,
local arrays,
procedure libraries (LIBRARY,INSTALL and OVERLAY),
LOCAL DATA and LOCAL ERROR handlers,
a relative RESTORE,
array operations,
new operators,
TRACE STEP,
Commands for the new sound system, mouse, graphics.

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 does nothing.) 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. Current versions of RISC OS still contain a BBC BASIC interpreter.

[edit] BBC BASIC on other platforms

BBC BASIC has also been ported to many other platforms [1].

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 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 subsquent 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.

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 specfication (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.

A GPL clone of BBC BASIC named Brandy written in portable C is also available.

A near-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, and 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.