Hi,
The default is unsigned char in the 'c' compiler I use for 8051
OK.
Please correct me if I write something wrong:
1. Keil implementation suppose "char" as "signed char".
2. You don't use C51 Keil compiler. (I wrote about Keil compiler in my prevoius comment because it is in the thread topic.)
3. It is better to use "signed ..." and or "unsigned ..." for data types. Reason: 'C' source portability.

Vaclav