Retained Earnings in BPC

Hi  All,

Can any one help me in the Area of Retained Earnings..Below are my questions:

1.How is Retained Earnings calculated in BPC? Is it a calculated figure or carried forward figure?

2. When it is calulated?

3.How it is carried forward from P&L account to B/S..Through any Business Rule or Script Logic.If so what are those rules/logic

Do you have any document on the same that could help to understant the above mentioned areas on Retained Earnings.

Thanks,

Shankar.v