Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!decwrl!pa.dec.com!rust.zso.dec.com!shlump.nac.dec.com!jareth.enet.dec.com!edp From: edp@jareth.enet.dec.com (Eric Postpischil (Always mount a scratch monkey.)) Newsgroups: comp.sys.handhelds Subject: Re: Re: The mythical bug-free code Message-ID: <19927@shlump.nac.dec.com> Date: 7 Feb 91 13:33:39 GMT References: <27b07042:1922.3comp.sys.handhelds;1@hpcvbbs.UUCP> <27af59f6:1922.2comp.sys.handhel Sender: newsdaemon@shlump.nac.dec.com Reply-To: edp@jareth.enet.dec.com (Eric Postpischil (Always mount a scratch monkey.)) Organization: Digital Equipment Corporation Lines: 24 In article <27b07042:1922.3comp.sys.handhelds;1@hpcvbbs.UUCP>, akcs.falco@hpcvbbs.UUCP (Andrey Dolgachev) writes: > . . .Along this >line, can you imagine if the testers tried every single HP command on >every possible combination of object type, and for every situation of >system flags, and then what happens if you press the on key right after >another key, and if you transfer 0 byte programs, etc., etc. Actually, we can calculate how long this would have taken. I'll suppose the 32Kb RAM is all there is. I haven't followed the hardware details, so add to that for whatever other machine states there are. I'm assuming no plug-in devices. Let's see, that gives us 262,144 bits, so there are 2^262,144 machine states. At each instant, we can have a variety of possible inputs to the machine: clock tick, 49 keys, infared photocell high/low, receive wire high/low -- 53 bits. If HP tested a googol of states/inputs per second, it would only take, let's see, 10 to the power of tens of thousands of universe life-times to completely validate the machine. No problem. -- edp (Eric Postpischil) "Always mount a scratch monkey." edp@jareth.enet.dec.com