Re: linking in OS/360, was The History of the ALGOL Effort

glen herrmannsfeldt <gah@ugcs.caltech.edu>
12 Sep 2006 21:57:48 -0400

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From: glen herrmannsfeldt <gah@ugcs.caltech.edu>
Newsgroups: comp.compilers
Date: 12 Sep 2006 21:57:48 -0400
Organization: Compilers Central
References: 06-08-082 06-08-086 06-08-105 06-08-138 06-09-050 06-09-053 06-09-065
Keywords: linker
Posted-Date: 12 Sep 2006 21:57:48 EDT

Peter Flass wrote:
(snip)


> John - I read his words that somewhat differently. If you look at
> PL/I(F), for example, you find a huge program composed of many small
> pieces, each linked separately into a small load module. The "overlays"
> are done using OS/360 LINK and XCTL macros rather than via the Linkage
> Editor. The execute loads a small root phase that links in turn to s
> series of second-level modules, each of which links to a series of
> third-level modules. I think three is it, but the important point is
> that none of this is done with the help of the Linkage Editor, but
> through dynamic allocation of storage and dynamic program loading.


That, and the fact that it will write the symbol table to disk if
needed, allows it to run in 44K (a 64K machine -20K for PCP).


Fortran H is a normal overlay structure designed to run in 256K
(at least that is what H is supposed to mean).


I believe many utilities are also dynamic (LINK and XCTL)
overlays, though I am not so sure which ones.


-- glen


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