What is a nullable Type? How to assign a default value to it? Are nested nullable types allowed?

What are nullable types?
Nullable types are those which can represent a null in addition to the normal range of values. It is an instance of System.Nullable.

How to assign a default value to it?
Use the ?? operator to assign a default value when it is assigned to a non-nullable type.
Ex:
int? empid=null;
int tempid= empid ?? 1;

Are nested nullable types allowed?
No.

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