user3336: The uno has digital pins marked 0-13. 
0 is marked as rx and 1 is marked as tx. 
Can these two pins be used as regular digital pins if i am short of digital pins?

user3004: Also you will probably want to ensure these wires are not connected when programming the Arduino. Otherwise you may have problems.

user84: Yes you can perfectly use these 2 pins as long as your program does not use Serial.
EDIT: Serial data over USB goes through copper traces connected to the rx and tx pins, connecting them to the USB to serial converter chip.

3336: <p>The uno has digital pins marked 0-13. </p>

<p>0 is marked as rx and 1 is marked as tx. 
Can these two pins be used as regular digital pins if i am short of digital pins?</p>
 3004: <p>Also you will probably want to ensure these wires are not connected when programming the Arduino. Otherwise you may have problems.</p>
 84: <p>Yes you can perfectly use these 2 pins as long as your program does not use <code>Serial</code>.</p>

<p>EDIT: Serial data over USB goes through copper traces connected to the rx and tx pins, connecting them to the USB to serial converter chip.</p>
