Re: Programming with API's

On Fri, 3 Aug 2001 SCarter@rsrcorp.com wrote:
> 
> I have been looking lately play around with API's and try to get a general
> feel for using them. I have a couple of questions:
> 
> 1.  Are the system supplied api's useful?  Is there any real business need
> to use these?

Yes, very very useful.  There are endless business needs that use them.
Of course, depending on what business you work in, you'll have different
needs....

> 2.  Where can I get a better description of what an API does than just
> looking at QSYSINC and QUSRTOOL?

I don't use QUSRTOOL, and haven't really looked at it.  The system 
APIs are all documented in the IBM manuals.

Here's the "System API Programming" manual from IBM.  This is where I
got my start with the IBM APIs.  It only gives examples of a few
APIs, but you learn the basics:

http://publib.boulder.ibm.com:80/cgi-bin/bookmgr/DOCNUM/SC41-5800-00


Here's the main reference info for the IBM APIs.  It has the reference
info for all of the APIs, but is not a tutorial:

http://publib.boulder.ibm.com/pubs/html/as400/v4r5/ic2924/info/rzaj5_frm.htm

Everyone else on the list has suggested the "Who Knew You could Do That"
Redbook...  I have to admit that I haven't used this RedBook, I learned 
this stuff before that book was written, so I can't really comment on it.

> 3.  Where can I get API's other than IBM? Or are API's only supplied by
> IBM?

An API is an interface to some software function that is intended to be
called from a program -- as opposed to interfacing directly with a user.
I'm sure you're familiar with the design and implementation of a "user
interface" an API is an "application program interface".  Instead of a
screen where a user can type information, it's a set of parameters 
where a program can supply information.   That's all it is.

So where can you get API's?  Everywhere.  In my shop, we have many APIs
that we developed in-house.  In addition, there are "APIs" in the
T.L. Ashford Barcode/400 software that we use to print labels (though,
TL Ashford doesn't use that term, they're really APIs)   The "Trustedlink
EDI/400" software from Peregrine (previously Harbinger/Premenos) has APIs
as part of the package.   The PER/ZIP4 software from Worksright Software
has APIs.   

Heck, I'm even involved in two open-source projects that provide APIs.
(See http://klement.dstorm.net/oss.html)  APIs are everywhere!

> 4.  None of the examples in QUSRTOOL are in RPG IV, should they be in RPG
> IV format and what do I have to do to get them in RPGIV format?

I don't use QUSRTOOL, and I don't want to comment.

> 
> 5.  And I am sure this has already been asked but.... Where can I get
> information, examples, books, etc.... about how to use API's with RPG
> IV.?(Not C )

I'm currently working on writing a tutorial for the sockets API for RPG
programmers, which will provide some examples.   (But, it's not quite
finished... still, if you poked around my site, you'd stumble on it)

Over the past few years, I've posted many API examples on this mailing
list, as have other people -- try searching the archives at
http://archive.midrange.com

There are simply too many APIs out there to have a single book that has
examples of EVERYTHING.  If there's a specific API that you can't find
a useful example of, post a message here.  Odds are pretty good that
someone will be able to provide one.   (If it's an API that I use, I'd
be happy to post an example)

Hope that helps you in some small way...


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