pdp11 BBC BASIC for the PDP11
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PDP11 BBC BASIC running on
PDP11 Unix Version 6 with an ASR33 Teletype
I started writing BBC BASIC for the PDP11 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 PDP11 UNIX TRAPs for I/O (eg TRAP 4 for character output and TRAP 3 for character input), so should run on any compliant PDP11 UNIX. With a suitable HostIO source BBC BASIC will run on other PDP11 systems. For example, TubeIO uses PDP11 Tube EMT calls for I/O and RTIO uses RT-11 EMT calls - and will run on RSTS which has an RT-11 API layer.

I have been testing PDP BASIC on UNIX Version 5, 6 and 7 running on the SIMH PDP11 and Ersatz-11 as well as my PDPTube emulator. The PDP11 core has been added to the BBC Matchbox Second Processor and the Tube version has been running on that as well. I have recently started testing on RT-11 on SIMH, E11 and the UKNC-BackToLife emulator.

BBC BASIC v0.36 (30-Jun-2020):
  • BBC BASIC for PDP11 Unix
  • BBC BASIC for PDP11 Tube
  • BBC BASIC for RT-11/RSTS
  • Brief overview
  • BBC BASIC documentation
  • Full BBC BASIC archive: source, docs, demos
  • DFS disk image
  • RT-11 disk image
  • Background documentation
  • Development blog

Running BBC BASIC on Unix
  • Download bbcbasic (15K, v0.36 30-Jun-2020).
  • 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.
  • Alternatively, download the bbcpdp.zip archive and extract it to your Unix system.
  • Boot into into Unix, log on and type bbcbasic at the user prompt.
  • bbcbasic is also directly runnable on PDPTube.
Running BBC BASIC on RT-11, RSTS and UKNC
  • Download basic.sav (15K, v0.36 30-Jun-2020) and copy the file to an appropriate RT-11 disk image with a tool such as putr.
  • Alternatively, download the bbcpdp.dsk disk image.
  • Boot into into RT-11 and type BASIC (or RUN xyz:BASIC where xyz: is the device name of the disk the BASIC.SAV file is on.
The source archive includes some demo programs and documentation.
Running BBC BASIC on a PDP11 Tube/CoPro
  • Download basic.rom (13K, v0.36 30-Jun-2020).
  • Load it into a bank of sideways RAM, or program it into an EPROM.
  • With the PDP11 CoProcessor enabled, PDP11 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.
  • bbcpdp.ssd contains some demo programs, as well as a copy of basic.rom.
  • bbcbasic and basic.sav are also directly runnable on PDPTube.

Install shows more detailed examples on running PDP11 BBC BASIC. You can also see blog entries following PDP11 BASIC's development.

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Last update: 30-Jun-2020