AVR-Chat

I'm attempting to use the Codevision compiler with a tiny2313.  
Unfortunately its been 7 years since I took C, so I'm quite rusty...

While I wait for the moderator of the codevisionavr group to approve my 
membership, I will post my question here. :)

If I write:
   putchar (0x55)   ; transmit ascii U out the serial port
it works as expected.

But if I write:
   putchar ("U")   ; transmit ascii U out the serial port
it throws a "possible loss of precision" warning and actually transmits 
ascii 8.

What am I missing?

Aaron