Warning #188-D pointless comparison of unsigned integer with zero for char

I'm getting this warning on line #9. It's almost like the char type is by default unsigned in the compiler. I believe this may be the case with the IAR compiler, but the cl430 compiler manual states that the char type is by default signed for this EABI data type. When I change the variable in line #5 to be a signed char the warning is removed. ?

Ref:-------------------------------------

Line #     Code

1          void TestCharDefaultType(void)
2          {
3            unsigned char smoc1;
4            unsigned char smoc2;
5            char result;

6            smoc1=10;
7            smoc2=3;
8            result=(char)smoc2 - (char)smoc1;
9            if (result < 0)
10             smoc1=2;
11         }