DeltaStreams file-out format and class model

Jecel Assumpcao Jr jecel at merlintec.com
Wed Oct 10 15:12:06 UTC 2007


Klaus D. Witzel wrote:
> On Wed, 10 Oct 2007 12:35:20 +0200, Bert Freudenberg wrote:
> > On Oct 10, 2007, at 11:54 , Klaus D. Witzel wrote:
> >> On Wed, 10 Oct 2007 10:37:44 +0200, Bert Freudenberg wrote:
> >>> It's incredibly flexible indeed, and goes back to the B5000 that  
> >>> inspired Smalltalk.
> >>
> >> Interesting. Having worked with almost all B5000 series and successors  
> >> and still working with them, what's the chunk format on them (besides  
> >> that it has no naked memory pointers, but descriptors)?
> >
> > Maybe I should have wrote "the idea goes back", not chunk format itself.  
> > The idea to have the data itself specify how to be processed comes from  
> > there - the tapes had a loader program in front that reads the rest of  
> > the tape. I don't know much about the details.
> 
> Ah, the clear/start & halt/load tapes :) still in use in emergency  
> situations, when disks are down. Will tell my colleagues about  
> clar/start's usage in Smalltalk code file chunks :)

I think Bert might have been thinking of the Burroughs 220 tape format
used in Air Training Command installation which was mentioned by Alan
Kay in his "The Early History Of Smalltalk".

Since most problems in computing can be solved by adding another level
of indirection, it might be nice to extend the chunk format so that when
you got an error while trying to create a reader due to missing classes
there were some hint on how to fix the problem automatically (by
downloading another file).

-- Jecel



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