Could anyone please tell me?

[punchinello]

What is a segment selector?
How is "overflow" defined in assembly programming language?

Thank you very much in advance!

[NotNull]

An Overflow in assembly occurs when the result of
an arithmetic instruction is larger than the destination
operand. For instance, a Divide Overflow occurs when
the quotient is larger than the operand used to store
the quotient part of the result.

A segment selector is a value placed in a segment register
which acts as an index into a table of segment descriptors
which define the attributes, rights, size, and address
of a segment. These segment descriptors enable the
processor to find the actual linear address of the segment
and to check if the application requesting its use has
a high enough privilege level (0 is the highest) to access it.
In other words it "selects" a segment, allowing an application
to access data contained in that area.

[punchinello]

Thank you very much!