how to define a serial inputString

Projects Programming
9 
Twitter(const char *user_and_passwd);

So a String won't work.

I'm guessing the string needs to be converted somehow to simple text for use?

Yep, or don't use the String class in the first place.

char inputString[40] ;    

   Serial.begin(9600);
   if (twitter.post(inputString)) {

Rob