that produced invalid operation when i tried it, not the stack underflow of the previous example. the result won't fit in a signed integer, and unsigned integer isn't supported by the hardware, so you get a trap as documented. in fact, the compiler could and probably should compensate by converting to and from 64-bit signed integers, which would also eliminate the test-and-skip mentioned earlier. i think 64-bit is supported, since it's listed with an opcode, although the textual description then claims `word- or short-integer format' only. it's an Intel handbook. ``beware DEC manuals'' the stack underflow is more likely to be a compiler problem. (stack overflow on the other hand is quite likely to be a missing prototype.)