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From: John Levine <johnl@taugh.com>
Newsgroups: comp.arch
Subject: Re: PDP-10 addressing, was The Design of Design
Date: Sat, 27 Apr 2024 16:38:15 -0000 (UTC)
Organization: Taughannock Networks
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According to Thomas Koenig  <tkoenig@netcologne.de>:
>> While this wasn't terribly hard, it did mean that any time you wanted
>> to change a program to run in extended mode you had to look at all the
>> code and check every instruction that did an address calculation,
>> which was tedious.
>
>Hmm... would a simple recompilation have done the trick, or were there
>also issues with integers being restricted to 18 bits, for example?

This was 50 years ago. The system software was mostly written in
assembler. Some was written in BLISS which was more concise but still
extremely machine specific. I suppose you could recompile your Fortran
programs, but the Fortran compiler was written in BLISS.

There were later versions of BLISS for the PDP=11, Vax and other
machines but they were not compatible with each other. The earliest
places I can think of system programming languages with different
targets were when Bell Labs ported Unix to the Interdata, and the IBM
S/38 and its successors that had (still has) a virtual machine
language that is translated to whatever hardware it's running on.

-- 
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