AS/400 How does it look?

[Terrence Enger]

On Sat, 2008-08-23 at 16:18 -0400, Christopher Browne wrote:
> On Sat, Aug 23, 2008 at 2:42 PM, William Muriithi
> <william.muriithi-Re5JQEeQqe8AvxtiuMwx3w at public.gmane.org> wrote:
> > Hallo there,
> >
> > I happen to notice that a lot of Canadian companies uses IBM AS/400.
> > However, I haven't been fortunate to come across it and I am curious
> > how it look. Does it have any familiarity to Unix? 

If you want to feel really at home, run Linux or AIX in a separate
partition.

Withing AS/400 you can feel somewhat at home, even though a lot of
installations choose not to display that facet of the system.  

(*) One of the command interpreters is quite similar to `bash`.  But if
you look closely you will notice oddities like the fact that `echo`
lacks the -n option, and `touch` has an extra option -C <codepage>.  And
a lot of the utilities you are used to having must be downloaded
separately.  Still, it is quite close enough to run a large part of the
cvs test suite with only minor tweaks.

(*) You have directories and files and pathnames.  But if you look
closely, you will notice that files have more permission bits than you
are used to.  And text files have an associated code pages.  And certain
mounted filesystems impose draconian limits on the names you can use.
And some of the files are in fact database tables, and these do not play
nicely with Unix utilities like `grep`.  And some of the files are
programs, which are not actually files at all.  I find all of these
qualifications are less problematic than they sound.

(*) You will feel completely at home with some features, for example,
the configuration files for the apache server, for example.

There are, as well, parts of the system which are quite different.
Being mostly familiar with these other parts, I cannot predict whether a
new arrival from a Unix background would find them on the one hand
merely strange or on the other hand very, very strange <grin />.

> What would be
> > reason that make it more popular in Canada than in USA?
> >
> > Just curious.
> 
> AS/400 is the latest iteration of IBM's "midrange" systems:
>  - System 34
>  - System 36
>  - System 38
>  - Then came AS/400, with OS called OS/400

Before the 34, there was the System/32, and before that the System/3.
Since the introduction of the AS/400 in 1988, IBM has changed the name
several times:  iSeries, i5, System i.

> 
> I'll bet that many of the apps running on AS/400 are actually from the
> predecessor platforms, running in emulation mode.

Code which was compiled on the System/36 and earlier is recompiled for
the AS/400 or whatever the nom-du-jour is.  The System/32, System/34,
and System/36 had an interpreted command language, and an "execution
environment" on the 400 interprets almost the whole language and more
besides.  The System/38 had its control language, which could be either
interpreted or compiled, and on the 400 that language can be either
interpreted or compiled.  So, the old programs are at least as well
integrated as the term "emulation mode" suggests.

Compiled programs from the System/38 as far back as 1978 run without
recompiling.  They automatically execute as 64-bit programs on the
current hardware.  When we get 96-bit hardware, they will run as 96-bit
programs.

Meanwhile, I believe--without ever having worked with it--that the AIX
emulation environment used to be more nearly "emulation".  I do not know
how true that is in the current generation of systems.
> 
> This is traditionally a platform where apps are mostly in COBOL and
> RPG, with BASIC and PL/1 as alternatives.  System 38 had the somewhat
> unique property of having a relational database (DB2) integrated into
> the OS.  (Microsoft was planning to "innovate" this in Longhorn; that
> seems rather late, as IBM did this in S/38 released in 1979!)

Is there any other released OS with integrated relational database?

E.S.Raymond, "The Art of Unix Programming"
<http://www.catb.org/~esr//writings/taoup/html/> makes a good case for
the value of "textuality".  But when you always have database facilities
available, they quickly become almost as useful.

> 
> It's sold *VERY* much as a platform for inventory and accounting
> systems, which is a very different branch from where Unix started
> (e.g. - research and document management).
> 
> I suspect that the reason why it's seen more in Canada than in the US
> is that, as a midrange system (as distinct from IBM's mainframe line),
> it was cheaper to deploy for localizing the management of "branch
> plants" in Canada for organizations based out of other countries (e.g.
> - US & UK).  The mainframes (e.g. - what was once S360, S370,
> eventually S390, and which is presently called "zSeries") would reside
> in the home countries, and cheaper "midrange" systems (S/34, S/36,
> S/38, AS/400, later "iSeries") would reside at branch operations in
> Canada.
> 
> That's a guess, but the once I saw S/34 was in a similar case.  I was
> working on getting a paper plant in Thunder Bay moved to new
> accounting software; they had been a branch plant of Abitibi Price,
> and the only "local" accounting was on a S/34-based system called
> ShawWare.  I'm pretty sure Abitibi-Price was on IBM mainframes.
> 
> There is *now* a Unix emulation layer in OS/400, but that's an add-on
> to support systems integration (e.g. - to let you get data on and off
> of it) as opposed to being a way you'd build apps natively for it.

Of the Unix-y environments, the AIX environment (shell program QP2SHELL)
is most accurately "emulation".  How does this do transfer or conversion
better than the other available facilities?  Or, do I misunderstand
something?

> The hardware has historically been exceedingly proprietary (in ways
> that used to cause people to consider IBM "evil" in the sorts of ways
> that they don't like Microsoft, today).
> 
> There are interesting aspects (in a "CS geek" sense) to S/38 and
> AS/400, but they're not likely to be too visible to typical users of
> the platforms.

And for this purpose, you can include application programmers with the
users (if you did not mean that already).  One of the reasons for my
productivity as a programmer--pay no attention to the jeering from the
cheap seats--is the vast amount of advanced technology which I need not
pay attention to.

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