# C - Bitwise OR operator

The Bitwise OR operator (|) is a binary operator which takes two bit patterns of equal length and performs the logical OR operation on each pair of corresponding bits. It returns 1 if either or both bits at the same position are 1, else returns 0.

Bit_1Bit_2Bit_1 | Bit_2
000
101
011
111

The example below describes how bitwise OR operator works:

```50 | 25 returns 59

50    ->    110010  (In Binary)
| 25    ->  | 011001  (In Binary)
----        --------
59    <-    111011  (In Binary)
```

The code of using Bitwise OR operator (|) is given below:

```#include <stdio.h>

int main (){
int x = 50;
int y = 25;
int z;

//Bitwise OR operation
z = x | y;

//Displaying the result
printf("z = %d\n", z);
return 0;
}
```

The output of the above code will be:

```z = 59
```

### Example: Find largest power of 2 less than or equal to given number

Consider an integer 1000. In the bit-wise format, it can be written as 1111101000. However, all bits are not written here. A complete representation will be 32 bit representation as given below:

```00000000000000000000001111101000
```

Performing N = N | (N>>i) operation, where i = 1, 2, 4, 8, 16 will change all right side bit to 1. When applied on 1000, the result in 32 bit representation is given below:

```00000000000000000000001111111111
```

Adding one to this result and then right shifting the result by one place will give largest power of 2 less than or equal to 1000.

```00000000000000000000001000000000
```

The below code will calculate the largest power of 2 less than or equal to given number.

```#include <stdio.h>

static int MaxPowerOfTwo(int N) {
//changing all right side bits to 1.
N = N | (N>>1);
N = N | (N>>2);
N = N | (N>>4);
N = N | (N>>8);
N = N | (N>>16);

//adding 1 to N makes smallest power
//of 2 greater than given number
N = N + 1;

//right shift by one position makes
//largest power of 2 less than or
//equal to given number
N = N >> 1;

return N;
}

int main() {
printf("MaxPowerOfTwo(100) = %d\n",
MaxPowerOfTwo(100));
printf("MaxPowerOfTwo(500) = %d\n",
MaxPowerOfTwo(500));
printf("MaxPowerOfTwo(1000) = %d\n",
MaxPowerOfTwo(1000));
return 0;
}
```

The above code will give the following output:

```MaxPowerOfTwo(100) = 64
MaxPowerOfTwo(500) = 256
MaxPowerOfTwo(1000) = 512
```

❮ C - Operators

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