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Re: Return of the Overlays!

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According to Don Y  <blockedofcourse@foo.invalid>:
>But, there is nothing in the traditional build process that
>ensures references from "some point" in the code don't refer
>back to some *other* point (that you thought you were done with).

Depends on your tools.

>Does anyone still develop with overlays (where the overlay has to
>replace the existing overlay at run time)?  Besides personal
>familiarity with the codebase, how do you select code portions
>to place in each overlay?

Still develop, no, but back in the 1980s I was one of the developers of Javelin,
a modelling package that ran on MS-DOS. We wrote it in Wizard C, which later
became Turbo C, in medium model so all of the static data was in one segment
that was always resident, with the code in each module in its own segment. We
used a third party linker that provided an overlay scheme similar to the OS/360
one I described in "Linkers and Loaders."

The linker let us (well, me) assign code modules to overlays and complained if
it saw calls that weren't strictly up or down the overlay tree. The digital
origami involved a lot of trial and error and guessing to see what in fact
caused overlay swapping, largely affected in our case by the way the users used
the program. There were about six views of the model of which you could put any
two on the screen at once, so I had to try and guess which views were likely to
be used together so I could put them in the same overlay.

-- 
Regards,
John Levine, johnl@taugh.com, Primary Perpetrator of "The Internet for Dummies",
Please consider the environment before reading this e-mail. https://jl.ly

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Return of the Overlays! Don Y <blockedofcourse@foo.invalid> - 2026-01-13 17:03 -0700
  Re: Return of the Overlays! George Neuner <gneuner2@comcast.net> - 2026-01-14 01:11 -0500
    Re: Return of the Overlays! Don Y <blockedofcourse@foo.invalid> - 2026-01-14 13:39 -0700
      Re: Return of the Overlays! George Neuner <gneuner2@comcast.net> - 2026-01-15 03:06 -0500
        Re: Return of the Overlays! Don Y <blockedofcourse@foo.invalid> - 2026-01-15 03:25 -0700
          Re: Return of the Overlays! George Neuner <gneuner2@comcast.net> - 2026-01-17 01:23 -0500
  Re: Return of the Overlays! John Levine <johnl@taugh.com> - 2026-01-14 20:39 +0000
    Re: Return of the Overlays! Grant Edwards <invalid@invalid.invalid> - 2026-01-14 21:00 +0000
      Re: Return of the Overlays! Don Y <blockedofcourse@foo.invalid> - 2026-01-14 18:55 -0700
    Re: Return of the Overlays! Don Y <blockedofcourse@foo.invalid> - 2026-01-14 18:48 -0700
  Re: Return of the Overlays! Don Y <blockedofcourse@foo.invalid> - 2026-01-25 01:46 -0700
    Re: Return of the Overlays! Don Y <blockedofcourse@foo.invalid> - 2026-01-25 02:10 -0700

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