An IBM Redpaper publication

Published 29 December 2007

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IBM Form #: REDP-4324-00
(75 pages)

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Authors: Gary Mullen-Schultz, Susan Gantner, Jon Paris, Paul Tuohy


The number of APIs supplied with a system increases from release to release. After belonging to the realm of the “advanced” programmer, APIs are playing an ever-increasing part in our day-to-day applications, for example, you might want an application program to be able to retrieve invoices from a spooled file, convert those spooled files to PDFs, and e-mail them to the relevant customer. By supplying such functions in the form of APIs, i5/OS® makes the functions available to C, COBOL, Java™ , and RPG programmers.

How many APIs are there? Well, back in 2003 there were over 1,500 APIs available to OS/400® developers. After that, we stopped counting!

Given the increased use of APIs, we decided to:
Describe how to find APIs
Explain how to interpret the API documentation
Explain how to use APIs

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