Thread: What does this struct for ?

  1. #1
    Registered User TmX's Avatar
    Join Date
    Sep 2006

    What does this struct for ?

    I forget where I got this snippet from.
    Anyway, here's the code

    struct foo {
    	char ch : 8;
    	int aaa : 2;
    	long bbb : 3;
    I don't think it's for creating arrays ...

  2. #2
    Registered User
    Join Date
    Apr 2006
    I don't know what it's supposed to do, but that stuct will contain 3 signed integers of size 8 bits, 2 bits, and 3 bits. The char, int, and long keywords have no effect in this case except to point out that it is a signed integer type; there is no difference between the three.
    It is too clear and so it is hard to see.
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  3. #3
    Registered User
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    May 2007
    ch goes from -128 to 127
    aaa from -2 to 1
    bbb from -4 to 3

  4. #4
    Registered User
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    Jul 2007
    char does not go from -127 to 127 I think. It is a char and it is unsigned. ??

  5. #5
    Deathray Engineer MacGyver's Avatar
    Join Date
    Mar 2007
    Quote Originally Posted by ozumsafa View Post
    char does not go from -127 to 127 I think. It is a char and it is unsigned. ??
    Actually, -128 to 127 is more or less the right range.

    A char is signed by default.

  6. #6
    Registered User
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    Sep 2006
    The integer arithmetic can be either two's complement, ones complement or sign-magnitude (though most modern machines use the first). The latter two have a symmetric range, the first has one extra on the minus side. Whether a char is signed or unsigned depends on the compiler (unlike other integral types which are signed by default), so to guarantee one or the other it's necessary to specify signed or unsigned explicitly.

  7. #7
    Frequently Quite Prolix dwks's Avatar
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    Apr 2005
    In fact, declaring a signed char is the only place you have to use the keyword signed. (That's why it was introduced, in fact.) Everywhere else it is optional.

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