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<concept id="GUID-27F345DA-7969-5B3B-B2BD-285CD168CF72" xml:lang="en"><title>Timers

And Timing Services Overview</title><shortdesc>Provides timers that asynchronously notify an application after

an interval or at a specific time.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

<section id="GUID-48022E0B-8764-4944-8CFF-5EE6956DBC7C"><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 id="GUID-59820FCE-FEF5-4089-8B62-1E1D8328437A"><title>Description</title> <p>The API has three key concepts: simple

timer, periodic timer, and heartbeat timer. </p> </section>

<section id="GUID-4CD59C91-C827-4C5A-98D4-509CBD3948EA"><title>Simple timer</title> <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> </section>

<section id="GUID-D44976FF-8171-47B8-A211-66541247F256"><title>Periodic timer</title><p><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> </section>

<section id="GUID-3D6DC89E-DE6A-4AE1-84E8-870AF4B70FC3"><title>Heartbeat timer</title> <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>

</conbody><related-links>

<link>

<desc><xref href="GUID-1294F540-FDA7-5050-BAFB-3C9888491B98.dita">Asynchronous

Services Overview</xref></desc>

</link>

<link href="GUID-FF8F5D97-7D37-5F6B-84A3-C064E2FD53E0.dita"><linktext>System Static

Functions Overview</linktext></link>

</related-links></concept>