Application Log & Backup files

Hi everybody,

I have two quaries..

1. In my program whenever errors occurs i am writing that error message in internal table and the same will be stored in application log.. here my query is how can we write error message in application log... can you explain the functionality of application log... do we need to define any internal table for application log.. please help me in tis regard.

2. I am creating four different named files in application server..... the same files will be taken backup in different backup folder.. how can i acheive this ....can anybody gone through this earlier...give me clear solution...

Thanks & Regards

R Nittala