Linking Companies and Linking Different Contacts within same company

[CJM]

I have two questions.  Im sure they have been asked before.

Question 1

For example: I have a company (Company A) who owns other companies with different names (Company B) how can i link those two companies together and still keep their own comany name.

Question 2

For example:  I have a company with the contact as the president.  Within that same company there is a CFO.  I can I have different contacts with in the same company.

Thanks in advance for your help.

Cory