The headers of pcDuino is compatible with Arduino Uno.  However, pcDuino provides an extra set of GPIOs. You can use them in case you want.

The following picture shows where these GPIOs are:

To use them, it is fairely easy. Actually it is exactly same as other pins.

#include <core.h>

#define Relay 23

void setup(){
pinMode(Relay, OUTPUT);

}

void loop(){
digitalWrite(Relay,HIGH);
delay(100);
digitalWrite(Relay, LOW);hai
delay(100);

}