"if "p1.0 pin" is held low by an external signal (although i have written a 1 on it), i would read p1.0 now (from the code) as 0.

is that right? "

Right. But would you be kind enough to tell what derivative you are using ? Then one can be sure about the answer.

And going back to your first question, the setup as described by you ( part of the port as input and part as output) is a regularly used configuration. Why, there are even cases where the SAME port pin is used both as an output and input.

( Despite the above you do have to read the basic tutorials as pointed out by Erik ! )

Raghu