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Problems with bit manipulation

This is a discussion on Problems with bit manipulation within the C++ Programming forums, part of the General Programming Boards category; I was trying to get a variable to represent all 1's. here is my code: unsigned long long x; x ...

  1. #1
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    Problems with bit manipulation

    I was trying to get a variable to represent all 1's. here is my code:

    unsigned long long x;
    x = ~0;

    cout << x << endl;

    when x is printed, it give me 18446744073709551615. I plug that into a calculator and it spits out a 1 followed by 64 zeros. Number 1. I thought long long was 64 bits (on a 32 bit machine) and not 65 and 2. why is it not all 1's? Is x the correct value and I just am not printing it out correctly?
    Last edited by redhawk87; 09-21-2011 at 09:20 PM.

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    ok, I tried printing it out using printf("%x", x) and printf("%d",x) and got 0xFFFFFFFF and -1 respectively. So it looks like it is working. So my question is, why does cout print a wrong value? Also does printf only print 32 bits? If so how can I get all 64 bits printed fairly easily?

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    Quote Originally Posted by anduril462 View Post
    Now, please, for the love of all things good and holy, think about what you're doing! Don't just run around willy-nilly, coding like a drunk two-year-old....
    Quote Originally Posted by quzah View Post
    ..... Just don't be surprised when I say you aren't using standard C anymore, and as such,are off in your own little universe that I will completely disregard.
    Warning: Some or all of my posted code may be non-standard and as such should not be used and in no case looked at.

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    Quote Originally Posted by redhawk87
    when x is printed, it give me 18446744073709551615. I plug that into a calculator and it spits out a 1 followed by 64 zeros.
    I plugged that into my calculator and it spits out 64 1s for the binary representation. Logically, looking at the decimal representation, this number must be odd, so it is impossible for the last bit to be a 0. I suspect a data entry error.
    iMalc likes this.
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