So is it correct to say you dont need the wire library if the lcd i2c library takes care of these commands.You still need the Wire library as the liquid crystal library uses it (calls wire functions). You still need to include the Wire library. Try not including it to see. To see what the functions and required function parameters are for a library, look at the header (.h) file. All member functions for that library (class) are declared there. The .cpp file has the member function definitions, ie the guts of the functions.