mouse@mcgill-vision.UUCP (der Mouse) (03/16/89)
In article <7390@killer.DALLAS.TX.US>, chasm@killer.DALLAS.TX.US (Charles Marslett) writes: > In article <9718@smoke.BRL.MIL>, gwyn@smoke.BRL.MIL (Doug Gwyn ) writes: >> In article <7309@killer.DALLAS.TX.US> chasm@killer.DALLAS.TX.US (Charles Marslett) writes: >>> To make it even more serious, I do not know of any twos-complement >>> computer that even has a signed vs. unsigned add instruction. >> They are one and the same. > You fell into the same "oops" I did: the IBM 360 had two different > instructions (has ...) that differ only in the way the condition > codes are set (overflow and the like). So there is a difference. There's this obscure (:-) machine called a VAX.... The add instruction sets *two* overflow flags, one indicating (for adds, at least) signed overflow and the other indicating unsigned overflow. (It also sets other flags, but they're irrelevant right now.) One of the flags is called a carry flag instead of an overflow flag, but I don't see that the name makes any difference.... der Mouse old: mcgill-vision!mouse new: mouse@larry.mcrcim.mcgill.edu