**Introduction**
Recently I got a task to implement a complex algorithm which involves lot of bitwise operation .After a bit struggle, I found a simple solution in C.

**BitArray Structure**
The easy and efficient way to store the bit information of a value is to create a structure as follows

typedef struct {
unsigned int bit : 1;
} Bit;
typedef struct {
Bit bitValues[BIT_ARRAY_LENGTH];
} BitArray;

**nth bit of an integer**
Here is the algorithm to findout the nth bit of an integer

nthBit of X =

1) Perform logical AND between X and 1

2) Right shift the result from step 1 n times

For example to findout the 3rd (4th position) bit of 171 (10101011)

tmp = 171 & (1 << 3)

result = tmp >> 3

The following function shows how to do this.

Bit getBit(int value, int position)
{
Bit singleBit;
singleBit.bit = 0;
if(position == 0) {
singleBit.bit = value & 1;
}else {
singleBit.bit = ( value & (1 << position ) ) >> position;
}
return singleBit;
}

**Integer value from the bit array**
We often require to convert back the bit array into the integer value. The following function does that.

int getValue(BitArray bitArray)
{
int value = 0;
unsigned int bitValue = 0;
bitValue = bitArray.bitValues[0].bit;
value |= bitValue;
for(int i = 1; i < BIT_ARRAY_LENGTH; i++)
{
bitValue = bitArray.bitValues[i].bit;
bitValue <<= i;
value |= bitValue;
}
return value;
}

**Example of Usage**
Imagine that we have to find out a secret key from a given value and the algorithm is as follows

->3rd bit of the value = 2nd bit of value XOR 3rd bit of value

->2nd bit of the value = 3rd bit of value XOR 1st bit of value

->1st bit of the value = 4th bit of value XOR 2nd bit of value

The following function shows how to do this by using our bitArray functions.

int calculateKey(int value) {
unsigned int key = 0;
BitArray bitArray = getBitArray(value);
bitArray.bitValues[3].bit = bitArray.bitValues[2].bit
^ bitArray.bitValues[3].bit;
bitArray.bitValues[2].bit = bitArray.bitValues[3].bit
^ bitArray.bitValues[1].bit;
bitArray.bitValues[1].bit = bitArray.bitValues[4].bit
^ bitArray.bitValues[2].bit;
key = getValue(bitArray);
return key;
}