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From: Michael S <already5chosen@yahoo.com>
Newsgroups: comp.arch
Subject: Re: branch address architecture, not interactive use, The Design of
 Design
Date: Tue, 14 May 2024 12:35:24 +0300
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On Tue, 14 May 2024 02:59:38 -0000 (UTC)
John Levine <johnl@taugh.com> wrote:

> According to MitchAlsup1 <mitchalsup@aol.com>:
> >    JSR PC,@(SP)+
> >
> >Popped the return address off the stack, pushed another return
> >address on the stack and transfers control. This is how we did
> >coroutines.  
> 
> When I was teaching an operating system class in about 1977 I
> challenged the class to come up with a minimal coroutine package. They
> all found that pretty quickly.
> 
> It's not very good coroutines since it just switches the return
> address, not any other stack context, but it can sometimes be useful.
> 
> 

I would guess that is was sometimes usefull in 1967, much less often
usefull 1977 and almost never useful (on "big" general-purpose
computers) in 1997 or later.