bsrdp@warwick.ac.uk (Hylton Boothroyd) (06/23/89)
A couple of years ago I wrote a short turbo pascal 3 programme to generate 8-character random alpha strings. I've just been surprised by the result of putting a copy in a .ZOO and running it under MSDOS 3.20 on an XT clone. Using looz xx zoohive rndname I get the same string each time: kkiioriv . Giving the programme a different name and putting it in a different .ZOO yields the same string! The command works OK at DOS command level - or more strictly at the DOS/CED command level that one of Rahul's remarks nudged me towards. The odd behaviour of this one programme is not important to me in itself. I just happened to use it as an example in testing out a set of command structures. What disturbs me is that I can't see why it might happen, and I therefore can't guess the class of circumstances in which there might be changed behaviour. Any comments? ----------------------- Hylton Boothroyd Janet: h.boothroyd@uk.ac.warwick.cu Warwick Business School Darpa: h.boothroyd%cu.warwick.ac.uk@relay-nsfnet.ac.uk University of Warwick Uucp: h.boothroyd%sol@warwick.uucp COVENTRY Earn/Bitnet: h.boothroyd%uk.ac.warwick.cu@UKACRL England CV4 7AL Phone: +44 203 523523 Extension 2428 -----------------------
leonard@bucket.UUCP (Leonard Erickson) (06/29/89)
In article <3008@sol.warwick.ac.uk> bsrdp@warwick.ac.uk (Hylton Boothroyd) writes:
<A couple of years ago I wrote a short turbo pascal 3 programme to generate
<8-character random alpha strings.
<
<I've just been surprised by the result of putting a copy in a .ZOO and
<running it under MSDOS 3.20 on an XT clone. Using
< looz xx zoohive rndname
<I get the same string each time:
< kkiioriv .
<
<Giving the programme a different name and putting it in a different .ZOO
<yields the same string!
<
<The command works OK at DOS command level - or more strictly at the DOS/CED
<command level that one of Rahul's remarks nudged me towards.
<
<The odd behaviour of this one programme is not important to me in itself. I
<just happened to use it as an example in testing out a set of command
<structures. What disturbs me is that I can't see why it might happen, and I
<therefore can't guess the class of circumstances in which there might be
<changed behaviour.
As I recall the random routines in TP3 use some chunk of memory for a seed.
When you run it from inside the Zoo file, this chunk of the DOS environment
will *always* be the same. Try putting the program in your autoexec and
you'll get the same kind of result.
Remember, programs *can't* generate truly random numbers, only psuedo-
random ones. If the machine state is the same, the output will be the same.
--
Leonard Erickson ...!tektronix!reed!percival!bucket!leonard
CIS: [70465,203]
"I'm all in favor of keeping dangerous weapons out of the hands of fools.
Let's start with typewriters." -- Solomon Short