bits in C

This is a discussion on bits in C within the C Programming forums, part of the General Programming Boards category; I do not know how to refer to bits in C and i need an example.Do i refer as char ...

  1. #1
    ch4
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    bits in C

    I do not know how to refer to bits in C and i need an example.Do i refer as char or as int.I do not know basic commands in bits.
    I just need an example...

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    Woof, woof! zacs7's Avatar
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    Last edited by zacs7; 07-10-2007 at 06:51 AM.

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    Dr Dipshi++ mike_g's Avatar
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    You should read up about 'bitwise operators' in C. There should be a tutorial here about it.

    For example if you want to check if the 32 bit in a byte is on you could use the bitwise 'and' opetator:
    Code:
    if(somenumber & 32)
    For setting a bit I would check if its set first, if not then just add the bit value to it.
    Code:
    if(!(somenumber & 32))somenumber+=32;
    This may not be the best way to do this tho.

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    Deathray Engineer MacGyver's Avatar
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    Quote Originally Posted by mike_g View Post
    For example if you want to check if the 32 bit in a byte is on you could use the bitwise 'and' opetator:
    Not to be pedantic, but a byte doesn't have a 32nd bit on most architectures.

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    Woof, woof! zacs7's Avatar
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    The tutorial covers all that in depth, and explains there's 8 bits to a byte, usually
    Last edited by zacs7; 07-10-2007 at 07:28 AM.

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    Dr Dipshi++ mike_g's Avatar
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    Er... I said 32 bit, not 32nd, but I guess it could seem confusing. I usually talk like that anyway with binary stuff and break ints down into octects. Plus it meant that I dident have to go into bitshifting with my explanation. But yeah, i'm sure the tutorial is better than my vague explanation.

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    Woof, woof! zacs7's Avatar
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    Ohh, I see where your coming from. Checking if the 32nd bit is on in a set of bytes, ie a byte (if you break it down)?

  8. #8
    The larch
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    For setting a bit I would check if its set first, if not then just add the bit value to it.
    Code:
    if(!(somenumber & 32))somenumber+=32;
    This may not be the best way to do this tho.
    Or or:
    Code:
    somenumber |= 32;
    I might be wrong.

    Thank you, anon. You sure know how to recognize different types of trees from quite a long way away.
    Quoted more than 1000 times (I hope).

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    Dr Dipshi++ mike_g's Avatar
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    Yeah, ORing its better. I forgot that

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    Captain Crash brewbuck's Avatar
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    Quote Originally Posted by MacGyver View Post
    Not to be pedantic, but a byte doesn't have a 32nd bit on most architectures.
    He said "32 bit" not "32nd bit." The 32 bit is the bit with value 32, in other words the fifth bit.

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    That bit would still be in one byte, as 32 in this case would be bit 5 (starting from bit 0).

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    Deathray Engineer MacGyver's Avatar
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    I get it now.... I just never think of the 5th (or 6th) bit as the "32 bit". lol....

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    >I get it now.... I just never think of the 5th (or 6th) bit as the "32 bit". lol....
    Me either. I would certainly use hex to write the same expression:
    Code:
    if (somenumber & 0x20)
    Or do a bit shift.

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