Hi Mahnoor Shamsi,

To make an i/o pin (a port pin) act as an input, you set the port bit to the logical high state. The internal circuitry pulls the pin high, but will source a current if you pull the pin low externally. On one of the ports the outputs are open collector (port 0 if I remember correctly). In any case, some of the other issues you will want to concern yourself with are debouncing, and always use external resistors to pull a pin high or low with a mechanical switch. There was an excellent discussion of all of this just a few days ago. Do a search for "internal pull up" and you should find the thread easily.

As for you English, it's horrible. But it's still a lot better than my Hindi, Farsi, Spanish, Chinese, Russian, Italian, Dutch, German, French, Portugese, et al, etc.....