||BBC BASIC for the PDP11
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
|PDP11 BBC BASIC running on|
PDP11 Unix Version 7
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
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 v0.34 (30-Jun-2020):
|Running BBC BASIC on Unix
Running BBC BASIC on RT-11, RSTS and UKNC
- Download bbcbasic (15K, v0.34 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
- 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
- bbcbasic is also directly runnable on
The source archive includes some demo programs and
- Download basic.sav (15K, v0.34 30-Jun-2020) and
copy the file to an appropriate RT-11 disk image with a tool such as
- 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.
|Running BBC BASIC on a PDP11 Tube/CoPro
- Download basic.rom (13K, v0.34 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>
- bbcpdp.ssd contains some demo programs, as well as a
copy of basic.rom.
- bbcbasic and basic.sav are also directly runnable on
Install shows more detailed examples on
running PDP11 BBC BASIC. You can also see blog entries
following PDP11 BASIC's development.
Authored by J.G.Harston
Last update: 30-Jun-2020