Binary Addition. Is it overflow?

Question

Binary values are in 2s Complement form.

If I am to add 110001 (-15) and 101110 (-18), and the answer has to be stored in a 6-bit integer, is this an underflow/overflow.

Answer 1

This is overflow, your professor is correct. You are storing more bits that can be held in the alloted space (even though the number that the bits represent is negative.)

Underflow is when bits get zero'd out through shifting on big math. Very common in fixed point math. Divide a very small number by a very big number and you will quite often get a 0. That is underflow.