Windows PowerShell 101 DVD Question

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jsclmedave
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Joined: Wed Mar 19, 2008 6:19 am

Windows PowerShell 101 DVD Question

Post by jsclmedave »

Question is -

Type the comparison that will allow PowerShell to determine if the fourth bit is "turned on" in the value 192.

Answer is -

129 -band 8
8 -band 129


I am at a loss here... If this is indeed correct can someone please explain?

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jsclmedave
Posts: 11
Joined: Wed Mar 19, 2008 6:19 am

Windows PowerShell 101 DVD Question

Post by jsclmedave »

Question is -

Type the comparison that will allow PowerShell to determine if the fourth bit is "turned on" in the value 192.

Answer is -

129 -band 8
8 -band 129


I am at a loss here... If this is indeed correct can someone please explain?

jvierra
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Joined: Tue May 22, 2007 9:57 am
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Windows PowerShell 101 DVD Question

Post by jvierra »

Bit 4 has a value of 8 when set.

2 ** (4-1) or 2 two the third power which is 2 * 2 * 2 or 8.

if bit and 8 matces bit by bit with 129 it will be true.

129 = 10000001 ( 128 + 1) or ( bit 8 + bit 1)
8 = 00001000

Does it match at the bit position.

Try 137 -band 8 it will tell you True.

false = 0
true <> 0

Try the following

[bool]0
[bool]1
[bool]-1

[bool](129 -band 8)
[bool](137 -band 8)
[bool](8 -band 8)

Now are you a believer?

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jsclmedave
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Joined: Wed Mar 19, 2008 6:19 am

Windows PowerShell 101 DVD Question

Post by jsclmedave »

Where does the 129 come in? They are all false which I get. The 4th BIT which is 8 in not true.

PS Z:> [bool]0FalsePS Z:> [bool]1TruePS Z:> [bool]-1TruePS Z:> [bool](129 -band 8)FalsePS Z:> [bool](137 -band 8)TruePS Z:> [bool](8 -band 8)TruePS Z:> [bool](8 -band 129)FalsePS Z:> [bool](8 -band 192)FalsePS Z:> [bool](192 -band 8)FalsePS Z:>

So shouldnt the answer to this question be - ?

192 -band 8
8 -band 192


It looks like a typo... If not I am completely lost as to where the 129 came from...

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donj
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Joined: Thu Nov 16, 2006 9:02 pm

Windows PowerShell 101 DVD Question

Post by donj »

Sorry, "192." Misread the question. But yes, the correct answer should be

8 -band 192

or

192 -band 8

If it isn't accepting that, then there may be a typo in the quiz module. It's also possible there's an extra or missing space; the quiz module is unfortunately extremely picky about that kind of thing.

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jsclmedave
Posts: 11
Joined: Wed Mar 19, 2008 6:19 am

Windows PowerShell 101 DVD Question

Post by jsclmedave »

Thank you all for the clarification and detailed information! Don - The module states the correct answer is - 129 -band 88 -band 129

So yes, I believe it

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