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<concept xml:lang="en" id="GUID-27F345DA-7969-5B3B-B2BD-285CD168CF72"><title>Timers And Timing Services Overview</title><prolog><metadata><keywords/></metadata></prolog><conbody><section><title>Purpose</title> <p>Provides timers that asynchronously notify an application after an interval or at a specific time.</p> </section> <section><title>Architectural relationships</title> <p>The <xref href="GUID-C197C9A7-EA05-3F24-9854-542E984C612D.dita"><apiname>User</apiname></xref> class in the System Static Functions API provides simple functions to suspend a thread for a given interval or until a specific time.</p> </section> <section><title>Description</title> <p>The API has three key concepts: simple timer, periodic timer, and heartbeat timer. </p> <p><b>Simple timer</b> </p> <p>The simple timer produces an event at a given system time or after a given interval. It is provided by <xref href="GUID-8A423EA2-4264-30C9-9579-0466994E6E88.dita"><apiname>RTimer</apiname></xref>. This service is wrapped in an active object by <xref href="GUID-5733DF34-5B54-3044-BBED-3BFECB7ACE7A.dita"><apiname>CTimer</apiname></xref>.</p> <p><b>Periodic timer</b> </p> <p>A periodic timer produces a sequence of events at a specified interval. The application is called through a callback (<xref href="GUID-6C5766BC-05DE-32A8-993D-6BB582931F43.dita"><apiname>TCallBack</apiname></xref>) when they occur. It is provided by <xref href="GUID-3CECC9FC-58C1-3117-AAF2-FDF88341F56F.dita"><apiname>CPeriodic</apiname></xref>.</p> <p><b>Heartbeat timer</b> </p> <p>A heartbeat timer is similar to a periodic timer. However, if the application is busy handling another event when the timer event occurs, a periodic timer simple delays delivering the event, while a heartbeat timer will inform the application that it has missed the event. </p> <p>It is provided by <xref href="GUID-12C497F2-DB51-3740-972C-11ACD6501DAB.dita"><apiname>CHeartbeat</apiname></xref>. Applications are alerted to timer events through implementing an interface <xref href="GUID-6DE7027A-54C0-33F1-B184-7070B1A85709.dita"><apiname>MBeating</apiname></xref>.</p> </section> <section><title>See also</title> <p><xref href="GUID-1294F540-FDA7-5050-BAFB-3C9888491B98.dita">Asynchronous Services Overview</xref> </p> <p><xref href="GUID-FF8F5D97-7D37-5F6B-84A3-C064E2FD53E0.dita">System Static Functions Overview</xref> </p> </section> </conbody></concept>