The IDL typeoctet, an 8-bit quantity, is mapped as an unsigned quantity to the typecorba:octet. The type specifiercorba:octet denotes the set of integers between 0 and 255, inclusive. This set can also be denoted by the type specifier(unsigned-byte 8).
For example:
(typep 255 'corba:octet) > T (typep -1 'corba:octet) > nil