HP C A.06.05 Reference Manual

Type Conversions
Integral Promotions
Chapter 4 77
To avoid situations where unsigned preserving and value preserving promotion
rules yield different results, you could refrain from using an unsigned char or
unsigned short in an expression that is used as an operand of one of the
following operators: >>, /, %, <, <=, >, or >=. Or remove the ambiguity by
using an explicit cast to specify the conversion you want.
If you enable ANSI migration warnings, the compiler will warn you of
situations where differences in the promotion rules might cause different
results. See “Compiling and Running HP C Programs” on page 207 for
information on enabling ANSI migration warnings.