What does this line do?

This is a discussion on What does this line do? within the C Programming forums, part of the General Programming Boards category; Hi, just reading through some code and got a little stuck as to the format in which this value is ...

  1. #1
    Matt Conway bobthebullet990's Avatar
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    What does this line do?

    Hi, just reading through some code and got a little stuck as to the format in which this value is writing to a string...

    Code:
    char string[128];
    int i;
    
    for (i=0; i<10;i++){
      printf("%08X\n", i);
    }
    I don't get what the output would be when doing %08x rather than just %x, and I get that by doing %x, you would print the hexidecimal value for at each loop.

    Thanks!
    Many junglists take pride in their belongin to what may be referred to as a globalised drum & bass subculture, as a subculture though, it is not nearly as distinct at gothic or punk!

  2. #2
    Kernel hacker
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    %08x means "fill with zeros to make it 8 digits, in hex".

    Similarly, you can use %8x, in which case it's filled with spaces instead of zeros, and %-8x would mean "fill with spaces AFTER the number to make it 8 positions". I don't think "%-08x" does anything sensible. (That is, it's probably no different from "%08x" - but it may behave strangely different from bugginess in any given imlementation).

    --
    Mats

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    Registered User whiteflags's Avatar
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    >I don't get what the output would be
    Run it and take a look then. Really. It's just a printf statement.

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    Matt Conway bobthebullet990's Avatar
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    Ok... so if i = 2, would output be:

    20000000

    or would it be

    00000002
    Many junglists take pride in their belongin to what may be referred to as a globalised drum & bass subculture, as a subculture though, it is not nearly as distinct at gothic or punk!

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    Kernel hacker
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    Quote Originally Posted by bobthebullet990 View Post
    Ok... so if i = 2, would output be:

    20000000

    or would it be

    00000002
    What do you think makes most sense (try it and see if you are right. you may want to count a tiny bit higher than 9 to make it show that it's hex!)

    --
    Mats

  6. #6
    Matt Conway bobthebullet990's Avatar
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    I would love to try it! ...would have saved me having to post, but I'm on a windows machine with no C compiler!!!!
    Many junglists take pride in their belongin to what may be referred to as a globalised drum & bass subculture, as a subculture though, it is not nearly as distinct at gothic or punk!

  7. #7
    Matt Conway bobthebullet990's Avatar
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    Well.. Im guessing it would pad before the digit! as padding after would be stupid! ...So i'm guessing that output would be:

    00000000
    ...
    00000009
    0000000A
    0000000B
    ....
    Many junglists take pride in their belongin to what may be referred to as a globalised drum & bass subculture, as a subculture though, it is not nearly as distinct at gothic or punk!

  8. #8
    Just Lurking Dave_Sinkula's Avatar
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    Quote Originally Posted by bobthebullet990 View Post
    I would love to try it! ...would have saved me having to post, but I'm on a windows machine with no C compiler!!!!
    http://www.compilers.net/Dir/Free/Compilers/CCpp.htm
    7. It is easier to write an incorrect program than understand a correct one.
    40. There are two ways to write error-free programs; only the third one works.*

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