some question about column constraints

hi,
I work on a tool that generates a creat script for an existing table.
My problem is to find out if a column is a constraint.
For example, I have the following creat script

create table abc(
xyz serial primary key
)

The metadata say that xyz is an int4 and not nullable.
Where I can recognize that it is a serial primary key?
Is it true that xyz always - if it is a serial primary key - will be
stored as a sequence like abc_xyz_seq?
how will others column constraints (check, unique) be stored?

Thanks,
Bjoern