Honored Contributor
Honored ContributorWell, since this is now over a month old, I'll try to point you in the right direction.
Most of these problems can be solved by carefully reading the error messages. In this case it says Signal "b[2]" drives an input pin. What this means is that vector (or multi-bit) signal is used to drive(output) a signal on an input pin. You cannot use an input pin as an output, only as an input. You can only use it to drive an input of a module lower in the hierarchy (such as the 4bitadder). A tip for the next time, just post the errors in text, the image resolution makes it difficult to read. p.s. Do you study at the HHS by any chance?
