SharePoint - Timer job in share point? how to create this one

refer these links-

 

http://msdn.microsoft.com/en-us/library/hh528519.aspx

for custom Timer job-

http://code.msdn.microsoft.com/sharepoint/SharePoint-2010-Custom-416cd3a1

Refer this link
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http://www.simple-talk.com/dotnet/.net-tools/a-complete-guide-to-writing-timer-jobs-in-sharepoint-2010/

http://sptimerjobadmin.codeplex.com/