This is the second of two articles discussing the basics of working with API-related data.

By Bruce Vining

When we left off in Part I, we were just calling the Retrieve Call Stack API, QWVRCSTK, for the first time. The program being discussed is repeated below. If you would like to review the API documentation, it can be found here.

In previous columns, we discussed the basics of API error handling and data types. Today, we'll talk about accessing and using information returned by retrieve type APIs.

By Bruce Vining

System APIs generally return information to you in one or more structures. One API that uses this approach, and that you might find handy to know about, is the Retrieve Call Stack (QWVRCSTK) API and format CSTK0100. This API and format is shown below and documented here.

If you search the 'net for ways to uppercase character data, you can find some really bad methods. But here's a really good one.

By Bruce Vining

Over the years, I have lost count of the number of times I have seen this question posed: "How do I uppercase character data?" And while the responses that I see on the Internet are getting better, I continue to see suggested "solutions" like the horrible "set the second bit on for each byte found in the range of a to z" (as shown in Figure 1) or the minimally correct "use the RPG %xlate function" (as shown in Figure 2). This first "solution" appears to work in a very restricted environment but has side effects, due to the EBCDIC collating sequence, that are not obvious. For instance, replace the value "Some character data" for variable CharData with the string "Some currency data like €100" and you will find that the Euro symbol € is "uppercased" to a symbol such as ÿ. Probably not the desired answer! The second "solution," though avoiding side effects such as the Euro being incorrectly "capitalized," does not support the full range of lowercase alphabetic characters (more on this a bit later).

By Bruce Vining

System APIs use a language-neutral convention when defining the type and size of data that is to be used as a parameter or a subfield of a data structure. A typical API parameter list would be the Retrieve Member Description QUSRMBRD API shown below and documented here.

Are you as knowledgeable about APIs as you should be?

By Bruce Vining

While it seems reasonable to assume that anyone reading RPG Developer is quite familiar with RPG, not every reader may be as familiar with the application program interfaces (APIs) available with i5/OS. In this ongoing column, "The API Corner," I will be discussing some of the wild and wonderful capabilities that are open to the RPG developer through system APIs. But the first few articles will be oriented toward the developer who, while knowledgeable about RPG, may not be that familiar with APIs.