Number of languages known [was Re: Python is readable] - somewhat OT

[Phil Runciman]

> -----Original Message-----
> From: Mark Lawrence [mailto:breamoreboy at yahoo.co.uk]
> Sent: Wednesday, 4 April 2012 3:16 a.m.
> To: python-list at python.org
> Subject: Re: Number of languages known [was Re: Python is readable] -
> somewhat OT
> 
> On 03/04/2012 15:56, Chris Angelico wrote:
> > On Wed, Apr 4, 2012 at 12:46 AM, Grant
> Edwards<invalid at invalid.invalid>  wrote:
> >> Anybody remember DEC's VAX/VMS "patch" utility?  Apparently, DEC
> >> thought it was a practical way to fix things.  It had a built-in
> >> assembler and let you "insert" new code into a function by
> >> auto-allocating a location for the new code an hooking it into the
> >> indicated spot with jump instructions.
> >>
> >> The mind wobbled.
> >
> > Not specifically, but I _have_ heard of various systems whose source
> > code and binary were multiple years divergent. It's actually not a
> > difficult trap to fall into, especially once you start patching
> > running systems. I've had quite a few computers that have been unable
> > to reboot without assistance, because they go for months or years
> > without ever having to go through that initial program load. (I've
> had
> > _programs_ that were unable to load, for the same reason.) But
> > auto-allocating a new spot for your expanded function? That's just...
> > awesome. My mind is, indeed, wobbling.
> >
> > ChrisA
> 
> Around 1990 I worked on Telematics kit.  The patches on all their
> software were implemented via assembler once the original binary had
> been loaded into memory.  They even came up with a system that let you
> select which patches you wanted and which you didn't, as e.g. some
> patches were customer specific.
> 
> --
> Cheers.
> 
> Mark Lawrence.
> 

In the 70's I worked with Honeywell 16 Series computers controlling a variety of systems. The patches were loaded as a starting address followed by machine code, using a piece of software for this purpose. This all sounds rather similar to Mark's situation. The reason however is less obvious. On the H16 series we did not have a multi-access O/S and the process of assembling and linking a large system involved many steps. Often the modifications required were trivial. It was generally easier to reload a memory dump from off paper tape and then apply the patches.


Phil Runciman