From:	Damian Yerrick <MYNAMEISd_yerrick AT hotmail DOT comNO2CANNEDHAM>
Newsgroups:	comp.os.msdos.programmer,comp.os.msdos.djgpp
Subject:	Re: Uptime and entropy in DOS
Organization:	Pin Eight Software http://pineight.8m.com/
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Date:	Sun, 13 Feb 2000 00:00:22 GMT
To:	djgpp AT delorie DOT com
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On Sat, 12 Feb 2000 18:13:37 GMT, manni DOT heumann AT gmx DOT de (Manni Heumann)
wrote:
>Damian Yerrick wrote:
>>Eli Zaretskii wrote:
>>>Damian Yerrick wrote:
>>>> 
>>>> Is it possible to get the uptime of a DOS system?  I need more entropy
>>>> than the 32 bits I get from time(NULL) to initialize a pseudorandom
>>>> number generator.
>>>
>>>Did you try `uclock' or `gettiomeofday'?.
>>
>>uclock() measures uptime of the current process, which is known
>>to be zero when I seed my PRNG.  gettimeofday() can be calculated
>>from time(NULL), which I'm already using.
>
>I'm nosy: Why isn't all of this enough for you?

Oh, now that I've rtfm again, it seems that srandom(time(NULL));
will work fine.  I've selected BSD random() (the new one with the
better seeder) with the obsolete advertising clauses removed
(Berkeley dropped them as of June 1999).
Is it possible to link BSD copyright files into a GPL program?

BSD random() seems to use the Apple RNG
  x = (x * 16807) % ((2 << 31) - 1);
to play with the seed.

>What about the user? How about a "Any key to continue" message
>and you measure the time it takes to answer that one

And watch people press the any key, anticipating the message, while
the game is showing the copyright/loading screen.

-- 
Damian Yerrick  http://yerricde.tripod.com/
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