Re: API Primer

[Vern Hamberg <vhamberg@xxxxxxxxxxxxxxxxxxxxxxxxx>]

Girish

Start at the Programming section in InfoCenter. There's a subsection on 
APIs (& CL, I think). The API Programming manual is there, as well a number 
of examples in various languages. Be sure to study the API Concepts section.

All the APIs are documented for use with C or C++. You'll need to get used 
to that syntax to understand better what they do. There are, however, a 
number of /COPY members for RPG and RPGLE in library QSYSINC. Some (in 
RPG/LE) you can use as is, others you may need to make a copy and add the 
non-fixed length parts. C can include a structure inside one of your own - 
AFAIK RPG/LE cannot do this - others may know better. This ability lets you 
not worry about release changes as much.

Very little is documented about using CL/LE for APIs, but it works quite 
well for those that use a user space or return data in a variable.

The documentation in InfoCenter includes API Concepts. Get to know user 
spaces very well, and how they are used in APIs.

If you use RPG/LE, learn about pointers - you'll have a much easier time of 
it. And you can have a pointer to a user space in RPG, allowing for 
automatic growth of what amounts to a character (or hex) buffer.

I agree with Al, to a point, that APIs are tough. But not all of them are. 
All they are is programs or service programs. The interface is defined, and 
you need to be careful to follow it exactly. But that's nothing new for 
anything we get from another developer. Once you get your feet a little 
wet, you'll be fine.

Some are definitely complex - the retrieve file description & query APIs 
are daunting, and almost impossible in RPG, since they are so dependent on 
pointers, and nested structures. Spooled file APIs, which offer a lot of 
functionality, are really a pain.

Enjoy!

Vern

At 06:37 PM 1/30/2003 -0500, you wrote:

> Could anyone suggest a good reference web site for using API's. I see soem 
> great ones referenced but wanted to see what else is
> available  what parametrs to use, any systems requirements and then (if 
> I'm not asking for too much already ) examples...
>
> thanks in advance...
>
> Girish