[Dwarf-Discuss] How best to represent multiple programs in a single file...

David Anderson davea42 at earthlink.net
Tue Jan 4 14:12:06 PST 2011


On 01/04/2011 01:08 PM, Relph, Richard wrote:
> Oh my... Overlays... I'd completely forgotten that term... But that you mentioned it and that I recognized it shows something about our age, doesn't it... ;-)
> But you're right, this is very much like the old MS-DOS (or was it CP/M?) style overlays of too many years ago.
The Wikipedia entry for "overlay (programming)"  Seems to be unaware of 
anything
earlier than the IBM PC!           Jean Sammet mentions all the basic
characteristics of overlays in  her 1969 book "Programming Languages, 
History and Fundamentals"
in a few sentences, though without any detail.  Look  for "overlays" in 
the index.

John R. Levine, in his book "Linkers and Loaders", says (p 177) "The 
final topic of this chapter
is tree-structured overlays, an approach that was widely used in the 
days before there was virtual
memory to fit a program into a memory area smaller than the program.  
Overlays are another
technique that dates back to before 1960 and are still in use in some 
memory-constrained environments."
and  "The OS 360 overlay manager is only about 500 bytes." (IBM OS 360 
debuted in 1964 with
quite a bit of flair and pizazz).

Sorry, off-topic.   But I did want to mention prior-art!
DavidA.



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