Differentiate between shippable and non shippable products

I want to add products which are not shippable and some products which are shippable.How to do it?

What shipping module(s) are you using?

What is suppose to happen with the non-shippable?

What determines the difference between the two Products?

I want to create two types of products under the product type subscription.
Types of products:
1)shippable--The products which we can ship to the shipping address mentioned.
2)non-shippable--The products which we can not ship they are only downloadable

This is already built in to Zen Cart ...

If a Product has an Attribute that has a Download filename on it, then it "knows" this is not for shipping ...

NOTE: Downloads are set up as:

Product is Virtual: No, Shipping Address Required

Always Free Shipping: No, Normal Shipping Rules

This way, the affect of the Download on shipping is not included for:
Price
Item Count
Weight