Becauseit would be ambiguous. 'ffh', for example, could either be a variable or a hex constant. But prefixed with a '0', it must be a numeric constant, because variables cannot start with a number. > Yes, 'cp 0F5h' will work - for some reason when you use "h" to identify a > value as hex the compiler asks for a "0" before the value... 'cp $F5' would > work as well.