Depite unparalled exposure and market saturation, the '''BBC Micro''' never made serious in-roads into the home computing market where it was beaten into third place by the much more affordable [[ZX Spectrum]] and [[Commodore 64]] until the arrival of the [[CPC|CPC 464]] pushed the ageing machine further down the pecking order.
The [[Acorn Electron]], a Spectrum-priced sibling of the BBC Micro, provides essentially the same software environment.
==Hardware==
[[File:BBC_Micro.jpg|right|350px|thumb|Standard BBC Micro]][[File:Acorn BBC Master Series.jpg|thumb|right|Acorn BBC Master 128]][[File:BBCMicro-PCB-layout.jpg|right|thumb|PCB Layout]]
While nine models were eventually produced with the BBC brand, the term '''BBC Micro''' is usually colloquially used to refer to the first six (Model A, B, B+64 and B+128, Master 128, Master Compact), with the subsequent models considered as part of the [[Acorn Archimedes|Archimedes]] series.
===BBC Master===
In 1986, [[Acorn]] followed up with the BBC Master, which offered memory sizes from 128 KB and many other refinements which improved on the 1981 original. At heart it was essentially the same 6502-based BBC architecture, with many of the upgrades that the original design had intentionally made possible (extra ROM software, extra paged RAM, second processors) now included on the circuit board as internal plug-in modules.
==Software==
Not all ROMs offered star commands (ROMs containing data files, for instance), but any ROM could claim certain vectors in order to extend the system's functionality. This feature was exploited in 1985 when Micro Power designed and marketed a Basic Extension Rom. This introduced new statements such as WHILE, ENDWHILE, CASE, WHEN, OTHERWISE, and ENDCASE, as well as many new direct mode commands including VERIFY. There were also DFS ROMs providing access to files on disc, and the Acorn GXR (Graphics eXtension ROM) added functionality to the VDU processing queue to allow flood fills and geometric shapes. Connecting an external EPROM programmer, one could write extensive programs, burn to PROM or EPROM, then run them without taxing user memory.
[[Acorn]] strongly discouraged programmers from directly accessing the system variables and hardware, favouring official system calls. This was ostensibly to make sure programs kept working when run on the Tube coprocessor, but it also made [https://www.romspedia.com/roms/bbc-micro BBC Micro] software more portable across the Acorn range. Whereas untrappable PEEKs and POKEs were commonly used on other computers to reach the system elements, both BBC BASIC and assembly language programs would instead pass parameters to an operating system routine. In this way the MOS could translate the request for the local machine's devices and memory layout or send it across the Tube interface, as direct access was impossible from the coprocessor. Published programs largely stuck to the API but games routinely made direct accesses for increased speed, and thus required a particular Acorn model or MOS version.
As the early '''BBC Micros''' had ample I/O allowing machines to be interconnected, and as many schools and universities employed the machines in Econet networks, numerous networked multiplayer games were created. With the exception of a tank game, ''Bolo'', few rose to popularity; in no small measure due to the limited number of machines aggregated in one place. A relatively late but well documented example can be found in a dissertation based on a ringed RS-423 interconnect.
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==Links==
*[[Media:BBC Microcomputer Advanced User Guide.pdf|BBC Micro - Advanced User Guide]]
*[[Media:Mullard SAA5050 datasheet.pdf|Mullard SAA5050 teletext chip datasheet]]
*[[Media:Texas instruments sn76489an.pdf|Texas Instruments SN76489AN sound chip datasheet]]
*[[Media:Intel 8271 FDC datasheet.pdf|Intel 8271 FDC datasheet]]
*[https://scarybeastsecurity.blogspot.com/2020/11/reverse-engineering-forgotten-1970s.html Reverse engineering the Intel 8271]
*[https://www.stardot.org.uk/forums/ Stardot.org.uk] Acorn computers forum
*[https://chrisacorns.computinghistory.org.uk/Computers/BBCMicros.html Chris's Acorns BBC microcomputers]
*[https://8bs.com/ BBC and Master Computer public domain library]
*[https://www.bbcmicro.co.uk/ Complete BBC Micro Games Archive]
*[https://youtu.be/a6r2QRTkqbc 1000 BBC Micro & Acorn Electron game clips]
*[https://youtu.be/T2VfgtTt5So Acorn Computers - Business Promo Video - Circa 1984]
*[https://youtu.be/bWGjEYMrm_0 Histoire, restauration et réparation BBC Micro] [https://youtu.be/kGYo2MOwslA Cette machine m'a bluffé !] by [[Rodrik Studio]]
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[[Category:Non CPC Computers]]