Truth Table#
| X | Y | X & Y | X | Y | X ^ Y |
|---|
| 0 | 0 | 0 | 0 | 0 |
| 0 | 1 | 0 | 1 | 1 |
| 1 | 0 | 0 | 1 | 1 |
| 1 | 1 | 1 | 1 | 0 |
Points to Remember#
- The left-shift and right-shift operators should not be used for negative numbers
- Left Shift(
<<) just means multiply by 2. Similarly >> results division by 2. XOR results 0 if both bits are same. So a^1=~a , a^0=a and a^a=0.
Questions#
- How to toggle or flip a particular bit in a number?
To toggle any bit in a variable, Use (^) exclusive OR operator.
#define togglebit(data, bit) (data* = data ^ (1<<bit))
- Write MACRO to Swap the bytes in 16bit Integer Variable.
#define ByteSwap16(Value) ((Value & 0x00FF) << 8) | ((Value & 0xFF00) >> 8)
#define ByteSwap32(Value) ((Value & 0x000000FF) << 24) |
((Value & 0x0000FF00U) << 8) |
((Value & 0x00FF0000U) >> 8) |
((Value & 0xFF000000U) >> 24)
- Count the number of set bits in a number
unsigned int countSetBits( unsigned int number )
{
unsigned int count = 0;
while( number != 0)
{
count++;
number &= (number-1);
}
return count;
}
- Swap 2 bits of given integer
int swapBits(unsigned int n, unsigned int p1, unsigned int p2)
{
unsigned int bit1 = (n >> p1) & 1; /* Move p1'th to rightmost side */
unsigned int bit2 = (n >> p2) & 1; /* Move p2'th to rightmost side */
unsigned int x = (bit1 ^ bit2); /* XOR the two bits */
/* Put the xor bit back to their original positions */
x = (x << p1) | (x << p2);
/* XOR 'x' with the original number so that the two sets are swapped */
unsigned int result = n ^ x;
}