|unsigned specifier||Unsigned integer type specifier|
simple-type-specifier := unsigned
The unsigned type specifier can be used with any integral type to make the type unsigned. Unsigned integer arithmetic is always performed modulo 2n, in which n is the number of bits in the value representation of the integer. When used alone, unsigned means unsigned int.
char c; if (isalpha(static_cast<unsigned char>(c)) handle_alpha(c);
char, int, long, short, signed, type, Chapter 2