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#1
03-21-2008
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Change Specific Value Of A Bit
char character has lenght 4 bytes .that means that is is 32 bit. how can ichange a value of a specific bit , for example the 15 bit of this sequence of 32 bit in C ?
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#2
03-21-2008
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Kinda vague - do you want to turn the bit on? off? flip the bit?
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#4
03-21-2008
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Your answer still was not clear. I think you want this:
Code:
x = x ^ mask; (or x ^= mask;) Bits that are set to 1 in the mask will be flipped in x. Bits that are set to 0 in the mask will be unchanged in x. Toggling (flipping) means that if the bit is 1, it is set to 0, and if the bit is 0, it is set to 1. XOR truth table 0 ^ 0 = 0 1 ^ 0 = 1 0 ^ 1 = 1 1 ^ 1 = 0
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#5
03-21-2008
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if you want to see which bit is set:
Code:
if(value & 1 ) -> true if first bit is set if(value & 2 ) second bit if(value & 4) third if(value & 8) fourth if(value & 16) fifth ... and so on
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#7
03-21-2008
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What platform are you on? All char type variables have a width of 8-bits so I'm not sure how you are getting a size of 32-bits for variables of char type.
Code:
#include <stdio.h>
int main(int argc, char **argv)
{
unsigned long i, j;
unsigned long var; /* variable whose 15th bit you want to test */
i = 0100000; /* unsigned octal has 15th bit set to 1 and the rest are 0 */
j = var & i;
if (j == i) /* if the 15th bit of var is set to 1 then j will equal i */
printf("15th bit is set to 1\n");
else /* if the 15th bit of var is set to 0 j will equal zero */
printf("15th bit is set to 0\n");
}
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