It is very unlikely that you will see more than one question dealing with Statutory Invention Registrations on the patent bar exam. The basics I outline here will provide you with more than enough information to prepare for this topic.

Statutory Invention Registration:
1. an original SIR can be abandoned and replaced by a continuing application:
2. in this case, the applicant will get the earlier filing date
3. the applicant must file an express abandonment of the original application and a timely request or petition to withdraw the request for an SIR prior to the publication of the SIR

Publication
1. nonprovisional utility and plant applications filed on or after November 29, 2000 are published promptly after the expiration of 18 months from the earliest filing date for which benefit is sought
2. nonprovisional applications entering the national stage from an international application filed on or after November 29, 2000 will also be published
a. this is regardless of whether the international application was published by the International Bureau under PCT Article 21 in English

The following applications will not be published:
1. provisionals
2. designs
3. reissues

Exceptions to publication include when:
1. the application is recognized by the Office as not pending
2. its status has been changed to abandoned by the Office and has been removed from the publication process
3. the application is under a secrecy order
4. the application has already issued in sufficient time for it to be removed from the publication process
5. however, the Office will not stop with the publication process until a patent actually issues
6. the application was filed with a nonpublication request

A rescission of a nonpublication request will never receive the benefit of a certificate of mailing or transmission. The USPTO will use the actual date of receipt at the Office.