@Yadav1, Welcome to the SAS Communities 🙂
The questions you have posted can be answered by a simple Google search.
If you want good answers in the community, please ask good questions and show us that you made an effort yourself.
You'll learn a lot faster by reading SAS's documentation on DATA step processing. For example:
I combined all your one-line questions into one, as the answers are the same for all:
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Learn the difference between classical and Bayesian statistical approaches and see a few PROC examples to perform Bayesian analysis in this video.
Find more tutorials on the SAS Users YouTube channel.