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136 lines
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<title>About application programming interfaces (APIs)</title>
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<body id="aboutapis"><a name="aboutapis"><!-- --></a>
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<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">About application programming interfaces (APIs)</h1>
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<div><p>Describes most of the iSeries™ application programming interfaces
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(APIs), as well as some APIs for related products that can be used on iSeries servers.</p>
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<p>Before using APIs, you should be familiar with the API concepts discussed
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in this topic. On occasion, you may need to refer to other IBM<sup>®</sup> books or topics
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for more specific information about a particular topic. Information for specific
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APIs or categories of APIs often provide links to additional information that
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may be useful to you.</p>
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<div class="section" id="aboutapis__who"><a name="aboutapis__who"><!-- --></a><h4 class="sectiontitle">Who should use APIs</h4><p>The APIs are intended
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for experienced application programmers who are developing system-level and
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other <span class="keyword">i5/OS™</span> applications.
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This topic provides reference information only; it is neither an introduction
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to the <span class="keyword">i5/OS</span> licensed program
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nor a guide to writing <span class="keyword">i5/OS</span> applications.</p>
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</div>
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<div class="section" id="aboutapis__how"><a name="aboutapis__how"><!-- --></a><h4 class="sectiontitle">How this information is organized</h4><p>In the
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API finder, you can search for APIs by category, by API name, by descriptive
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name, or by part of the name. You also can search for new APIs, changed APIs,
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and exit programs.</p>
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<p>The API categories are major functional categories,
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such as backup and recovery, objects, and work management. Within the individual
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categories, the APIs are organized in alphabetical order as follows:</p>
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<ul><li>By the spelled-out name for the original program model (OPM), the Integrated
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Language Environment<sup>®</sup> (ILE), and the ILE CEE APIs.</li>
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<li>By the function name for the UNIX-type APIs.</li>
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</ul>
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</div>
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<div class="section" id="aboutapis__compat"><a name="aboutapis__compat"><!-- --></a><h4 class="sectiontitle">Compatibility with future releases</h4><p>In
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future releases, IBM intends that one of the following will be true:</p>
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<ul><li>If additional input or output parameters are provided for any of the APIs,
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the new parameters will be placed after the current parameters and will be
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optional parameters. The existing APIs will continue to work without any changes.</li>
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<li>If an additional data structure is provided, a new format (layout of that
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data structure) will be created.</li>
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<li>New information may be added to the end of an existing format.</li>
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</ul>
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<p>It is IBM's intention that the APIs will continue to work as they
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originally worked and any existing applications that use the APIs will continue
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to work without changes. Significant architectural changes, however, may necessitate
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incompatible changes. Additionally, some API definitions, for example the UNIX<sup>®</sup> type
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of API definitions, are established by industry standards organizations where
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the degree of compatibility is determined by the organizations. </p>
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<p>To
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ensure better compatibility with future releases, you should retrieve and
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use all of the following when you work with user spaces generated by list
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APIs:</p>
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<ul><li>Offset values to the list data section</li>
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<li>Size of the list data section</li>
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<li>Number of list entries</li>
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<li>Size of each entry</li>
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</ul>
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</div>
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<div class="section" id="aboutapis__whenapi"><a name="aboutapis__whenapi"><!-- --></a><h4 class="sectiontitle">System APIs or CL commands--when to use each</h4><p>Before
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system APIs were offered on the system, you had to either code separate CL
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programs to perform the needed functions using the appropriate CL commands
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or code a call to the<span class="apiname"> Execute Command (QCMDEXC)</span> API in
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your program. Both methods made coding an application on the system more cumbersome
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(less straightforward and not as fast as possible).</p>
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<p>CL commands will
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always be needed; they are ideal for the interactive user and for CL applications
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that are performing basic tasks. They provide a complete set of functions
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on the system.</p>
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<p>APIs are not provided as a replacement for CL commands,
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although in many cases there may be both an API and a CL command that perform
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the same function. If a CL command and an API provide the same function, at
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times the API provides more flexibility and information. The CL command is
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intended to be entered either interactively or in a CL program, and the API
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is designed as a programming interface.</p>
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<p>Some APIs have no equivalent
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CL command. These APIs have been provided in areas where customers and business
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partners have indicated that they need high-level language (HLL) access.</p>
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</div>
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<div class="section" id="aboutapis__act"><a name="aboutapis__act"><!-- --></a><h4 class="sectiontitle">Actions and system functions of APIs</h4><p>An
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API can be categorized by the type of action it performs and by the system
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function that it relates to.</p>
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<p>Following are some of the types of APIs
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that perform actions; several examples of these APIs are discussed in more
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detail in later chapters of this book.</p>
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<ul><li>List APIs, which return lists of information about something on the system.</li>
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<li>Retrieve APIs, which return information to the application program.</li>
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<li>Create, change, and delete APIs, which work with objects of a specified
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type on the system.</li>
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<li>Other APIs, which perform a variety of actions on the system.</li>
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</ul>
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<p>While many APIs are used alone, some can be used together to perform
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a task or function. The following is a list of a few functions:</p>
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<ul><li>Defining, creating, distributing, and maintaining your own software products.</li>
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<li>Controlling systems and networks, which can include configuration, spooled
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files, network management, problem management, and so forth.</li>
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<li>Handling objects, which includes creating, changing, copying, deleting,
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moving, and renaming objects on the system.</li>
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</ul>
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</div>
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</div>
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<div>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="concept.htm" title="Describes the underlying concepts that you need to understand to work effectively with APIs. Among the concepts covered are basic concepts, programming considerations, and terminology.">API concepts</a></div>
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</div>
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<div class="relref"><strong>Related reference</strong><br />
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<div><a href="exdqdetermine.htm" title="If user queues and data queues supply the same function, which one should you choose for your implementation? The following is a comparison of the two and an insight into when you should use one queue rather than the other.">Determining whether to use data queues or user queues</a></div>
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<div><a href="ExTaskDataque.htm" title="Data queues and user queues both provide a means for one or more processes to communicate asynchronously. The queues can be processed FIFO (first-in first-out), LIFO (last-in first-out), or by key.">Examples: Using data queues or user queues</a></div>
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</div>
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</div>
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</body>
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