How to Set, Clear, Check, Toggle and Copy Bits in ANSI C

In the examples below, I will use the uint8_t primitive data type from the stdint.h ANSI library. If you never used this datatype or if you find this article a little tough to understand you may want to read this first. 

1.Setting a bit

Description
Setting the x-th bit of a number means changing the x-th bit value to 1.
Example
Considering a number a = 36, we shall set its 6th bit.

Bits	7th	6th	5th	4th	3rd	2nd	1st	0th
a	0	0	0	1	0	1	0	0	36
a set 6	0	1	0	1	0	1	0	0	100

Syntax

#include<stdio.h>
#include<stdint.h>

int main(void)
{
   uint8_t a=36;
   uint8_t b=6;
   a |= (1<<b);
   printf("a set b : %u",a);
   return 0;
}
/*Output
a set b : 100
*/

2.Clearing a bit

Description
Clearing the x-th bit of a number means changing the x-th bit value to 0.
Example

Bits	7th	6th	5th	4th	3rd	2nd	1st	0th
a	0	0	1	0	0	1	0	0	36
a clear 5	0	0	0	0	0	1	0	0	4

Syntax

#include<stdio.h>
#include<stdint.h>

int main(void)
{
   uint8_t a=100;
   uint8_t b=6;
   a &= ~(1<<b);
   printf("a clr b : %u",a);
   return 0;
}
/*Output
a clr b : 36
*/

3.Checking a bit

Description
Checking the x-th bit of a number means verifying the value of x-th bit (which can be 0 or 1).
Example:
a = 36 = 0010 0100
After checking the 5th bit, the value which is returned should be 1.
Syntax

#include<stdio.h>
#include<stdint.h>

int main(void)
{
   uint8_t a=100;
   uint8_t b=6;
   uint8_t checkResult = a & (1<<b);
   printf("a chk b : %u",checkResult);
   return 0;
}
/*Output
a chk b : 64
*/

4.Toggling a bit

Toggling the x-th bit of a number means changing its current value to its complementary value (if the bit is 1, it will be 0 and if the bit is 0 it will be 1).
Example:

Bits	7th	6th	5th	4th	3rd	2nd	1st	0th
a	0	0	1	0	0	1	0	0	36
a toggle 1	0	0	0	0	0	1	0	1	37
a toggle 5	0	0	0	0	0	1	0	0	4

Syntax

#include<stdio.h>
#include<stdint.h>

int main(void)
{
   uint8_t a=36;
   uint8_t b=5;
   a ^= (1<<b);
   printf("a tgl b : %u",a);
   return 0;
}
/*Output
a tgl b : 4
*/

5.Copying bits from a number to another

Description
Copying bits means that you modify certain bits of a number according to the same certain bits of another number. Those "certain bits" are called a mask.
Example:
Let us consider two numbers a and b where a = 36 and b = 6. We will want concatenate the first 4 bits of a and the last 4 bits of b. In order to do this we shall define a mask who needs to have the bits we want to get from a set to 1 and the bits we want to get from b set to 0. So mask will be equal to 240.

Bits	7th	6th	5th	4th	3rd	2nd	1st	0th
a	0	0	1	0	0	1	0	0	36
b	0	0	0	0	0	1	1	0	6
mask	1	1	1	1	0	0	0	0	240
~mask	0	0	0	0	1	1	1	1	15

In order to concatenate a and b, we will need to clear the bits we do not want to be in the final number by using the AND operator. Then we shall concatenate the results using the OR operator.
a' = a AND mask 
b' = b AND (~mask)
res = a' OR b' 

Bits	7th	6th	5th	4th	3rd	2nd	1st	0th
a	0	0	1	0	0	1	0	0	36
b	0	0	0	0	0	1	1	0	6
mask	1	1	1	1	0	0	0	0	240
~mask	0	0	0	0	1	1	1	1	15
a & (mask)	0	0	1	0	0	0	0	0	32
b & (~mask)	0	0	0	0	0	1	1	0	6
a' | b'	0	0	1	0	0	1	1	0	38

Syntax

#include<stdio.h>
#include<stdint.h>

int main(void)
{
   uint8_t a=36;
   uint8_t b=6;
   uint8_t mask = 240;
   a = (a&mask)|( b&(~mask) );
   printf("a cpy b : %u",a);
   return 0;
}
/*Output
a cpy b : 38
*/

Since these operations are used often (especially on embedded systems), here are some macros for them:

#define BitSet(a,b)       ( (a) |=  ( 1<<(b) ) ) 
#define BitClear(a,b)     ( (a) &= ~( 1<<(b) ) )
#define BitCheck(a,b)     ( (a) &   ( 1<<(b) ) ) 
#define BitToggle(a,b)    ( (a) ^=  ( 1<<(b) ) )
#define BitCopy(a,mask,b) ( (a) = ( (a) & (mask) )|( (b) & (~(mask) ) ) 

Question: How often do you use in projects these bitwise operations?

References:
http://stackoverflow.com/questions/47981/how-do-you-set-clear-and-toggle-a-single-bit-in-c