pdp11 BBC BASIC for the PDP-11
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PDP-11 BBC BASIC running on
the Matchbox PDP-11 CoProcessor
I started writing BBC BASIC for the PDP-11 at university on the late 1980s. It got as far as starting up, producing its startup message and prompting for input. A few years ago I wrote a PDP emulator and assembler and resumed work on completing it.

BBC BASIC uses standard PDP-11 UNIX TRAPs for I/O (eg TRAP 4 for character output and TRAP 3 for character input), so should run on any compliant PDP-11 UNIX. With a suitable HostIO source BBC BASIC will run on other PDP-11 systems, eg on RSX-11. For example, TubeIO uses PDP-11 Tube EMT calls for I/O.

I have been testing PDP BASIC on UNIX Version 6 and Version 7 running on the SIMH PDP-11 and Ersatz-11 as well as my PDPTube emulator. Recently the PDP-11 core has been added to the BBC Matchbox Second Processor and the Tube version has been running on that as well.

BBC BASIC v0.27 (04-Aug-2018):
  • BBC BASIC for PDP-11 Unix
  • BBC BASIC for PDP-11 Tube
  • Brief overview
  • BBC BASIC documentation
  • Full BBC BASIC archive: source, docs, demos
  • PDP-11 BASIC demo programs (DFS image)
  • Background documentation
  • Development blog

Running BBC BASIC on Unix
  • Download bbcbasic (15K, v0.27, 04-Aug-2018).
  • Copy the file to an appropriate directory or into a Unix disk image with a tool such as putr or UxFiler with 'execute by all' permissions (eg chmod 755). On Unix a suitable location is usually /usr/bin/bbcbasic.
  • Boot into into Unix, log on and type bbcbasic at the user prompt. The source archive includes some demo programs and documentation.
  • bbcbasic is also directly runnable on PDPTube.
Running BBC BASIC on a PDP-11 Tube/CoPro
  • Download basic.rom (13K, v0.27, 04-Aug-2017).
  • Load it into a bank of sideways RAM, or program it into an EPROM.
  • With the PDP-11 CoProcessor enabled, PDP-11 BASIC will be the default language and will be entered on Break or with *BASIC.
  • Alternatively, the basic.rom file can be run from the PDP11> prompt.
  • Demos.ssd contains some demo programs, as well as a copy of basic.rom.
  • bbcbasic is also directly runnable on PDPTube.

Install shows more detailed examples on running PDP-11 BBC BASIC. You can also see blog entries following PDP-11 BASIC's development.

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Last update: 04-Aug-2018