[fpc-other] Yet another mainframe emulator

[Mark Morgan Lloyd]

I thought this might interest some people because on the one hand it's a 
significant part of the history of ALGOL-derived languages, and on the 
other the implementation is deeply weird.

As some might recall, Burroughs had a range of "Large System" computers 
from the 1960s through '80s which were oriented to running ALGOL and 
related languages, with hardware-assisted stacks, a descriptor-oriented 
architecture and so on. These are frequently described as being 
programmable /only/ in ALGOL, i.e. there was no lower-level language, 
but in practice the machine-level opcodes were accessible to those of us 
who had to know, i.e. the maintenance guys and the people who had to 
configure initial boot (sometimes via a binary punched card, to tell the 
CPU how to find the disk pack with the MCP). [1]

Doctrine has it that Knuth and Dijkstra were involved to some extent as 
advocates of the architecture. It's unarguable that lots of people cited 
it as influential, e.g. Alan Kay (Smalltalk) and Charles Moore (Forth). 
There was a fairly good range of languages available, some from 
Burroughs but others from various univerisites.

It appears that somebody has written an emulator for the B5500, and it 
is able to boot the MCP extracted from tapes somebody had on their shelf 
and to run compilers. [2] [3] Also other people are finding listings (if 
not machine-readable media) of other software, e.g. an APL system 
written by a number of people including Gary Kildall (CP/M). [4] [5]

The really weird thing is that they've written this in Javascript, to 
run in a browser. In my opinion that's utterly crazy: a far better 
choice would have been ALGOL (possibly via Pascal) so that in principle 
at least the system could have been self-hosting.

So while I've got absolutely no intention of getting involved (the 
Burroughs Large System range is /dead/, in a way that e.g. the IBM S/370 
isn't) I think that it raises an interesting question: is it possible to 
mechanically translate from Javascript to Free Pascal?

After all, if one developer has decided to use Javascript there might be 
others. And in some cases what they're working on might actually be 
useful to a wider community.

[1] http://en.wikipedia.org/wiki/Burroughs_large_systems
[2] http://code.google.com/p/retro-b5500/w/list
[3] http://www.phkimpel.us/B5500/webSite/SoftwareRequest.html
[4] 
http://bitsavers.trailing-edge.com/pdf/burroughs/B5000_5500_5700/listing/
[5] 
http://www.softwarepreservation.org/projects/apl/APLSoftware/APLSystems/B5500%20APL/

-- 
Mark Morgan Lloyd
markMLl .AT. telemetry.co .DOT. uk

[Opinions above are the author's, not those of his employers or colleagues]