Re: The History of the ALGOL Effort

Henry Spencer wrote:
> Peter Ludemann <p_ludemann@yahoo.com> wrote:
>
>>One of the nice properties of the PL360 compiler is that it could
>>compile a program, produce a listing, and cross-references faster than
>>IBM's IEBPTPCH utility could produce only a listing.


> This experience had wider ramifications, too: PL360 compiled so much
> faster than IBM's glacially-slow linker could link, that it soured Wirth
> on separate compilation. The result was several influential languages,
> most notably Pascal, with no provision for separate compilation.


I finally just finally got around to reading _The Mythical Man-Month_,
and Fred Brooks has some comments on the OS/360 Linkage Editor. His
thesis is that it's the final culmination of the overlay linkers in
previous systems, such as the 7094 -- whatever they would have wanted
there got thrown into OS/360, making it very slow. At the same time
OS/360 got, and made extensive use of, dynamic linking, that made most
of the features of the Linkage Editor obsolete. Unfortunately, the
two development groups didn't communicate too well...


[That's not really what he said on page 56. OS didn't have dynamic
linking in the modern sense. What it did have was the ability to
allocate storage dynamically to each program. OS programs used static
overlays extensively, probably too extensively. IEWL, the link editor,
was heavily overlaid so it could run in a tiny amount of storage, like
8K bytes, at the cost of dreadful performance as it read in all those
overlays. But in the 99% of the cases where it had a whole lot more
than 8K available, since the overlay structure was fixed at link time,
it still did all the overlays and was just as slow. One of the nicest
things about virtual memory is that it automatically sizes to the
amount of real storage you have, so if you attach more memory, your
programs automatically run faster. -John]

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