a C language code to implement the Binary Search algorithm.

int binarySearch(int arr[],int size, int item)
{
int left, right, middle;
left = 0;
right = size-1;

while(left <= right)
{
middle = ((left + right)/2);

if(item == arr[middle])
{
return(middle);
}

if(item > arr[middle])
{
left = middle+1;
}
else
{
right = middle-1;
}
}

return(-1);
}



Note that the Binary Search algorithm has a prerequisite that the array passed to it must be already sorted in ascending order. This will not work on an unsorted array. The complexity of this algorithm is O(log(n)).